/* SPDX-FileCopyrightText: 2007 by Janne Karhu. All rights reserved.
 *
 * SPDX-License-Identifier: GPL-2.0-or-later */

/** \file
 * \ingroup bke
 */

/* Allow using deprecated functionality for .blend file I/O. */
#include "BKE_report.hh"
#define DNA_DEPRECATED_ALLOW

#include <algorithm>
#include <cmath>
#include <cstdlib>
#include <cstring>
#include <optional>

#include "MEM_guardedalloc.h"

#include "DNA_cloth_types.h"
#include "DNA_collection_types.h"
#include "DNA_curve_types.h"
#include "DNA_dynamicpaint_types.h"
#include "DNA_fluid_types.h"
#include "DNA_key_types.h"
#include "DNA_material_types.h"
#include "DNA_mesh_types.h"
#include "DNA_meshdata_types.h"
#include "DNA_object_force_types.h"
#include "DNA_particle_types.h"
#include "DNA_scene_types.h"
#include "DNA_texture_types.h"

#include "BLI_kdopbvh.hh"
#include "BLI_kdtree.hh"
#include "BLI_linklist.h"
#include "BLI_listbase.h"
#include "BLI_math_base_safe.h"
#include "BLI_math_geom.h"
#include "BLI_math_matrix.h"
#include "BLI_math_rotation.h"
#include "BLI_math_vector.h"
#include "BLI_rand.h"
#include "BLI_string_utf8.h"
#include "BLI_task.h"
#include "BLI_threads.h"
#include "BLI_utildefines.h"

#include "BLT_translation.hh"

#include "BKE_anim_path.h"
#include "BKE_boids.h"
#include "BKE_cloth.hh"
#include "BKE_collection.hh"
#include "BKE_colortools.hh"
#include "BKE_customdata.hh"
#include "BKE_deform.hh"
#include "BKE_displist.h"
#include "BKE_effect.h"
#include "BKE_idtype.hh"
#include "BKE_key.hh"
#include "BKE_lattice.hh"
#include "BKE_layer.hh"
#include "BKE_lib_id.hh"
#include "BKE_lib_query.hh"
#include "BKE_material.hh"
#include "BKE_mesh.hh"
#include "BKE_mesh_legacy_convert.hh"
#include "BKE_modifier.hh"
#include "BKE_object.hh"
#include "BKE_particle.h"
#include "BKE_pointcache.h"
#include "BKE_scene.hh"
#include "BKE_texture.h"

#include "DEG_depsgraph.hh"
#include "DEG_depsgraph_build.hh"
#include "DEG_depsgraph_query.hh"

#include "RE_texture.h"

#include "BLO_read_write.hh"

#include "particle_private.h"

namespace blender {

static void fluid_free_settings(SPHFluidSettings *fluid);

static void particle_settings_init(ID *id)
{
  ParticleSettings *particle_settings = id_cast<ParticleSettings *>(id);
  INIT_DEFAULT_STRUCT_AFTER(particle_settings, id);

  particle_settings->effector_weights = BKE_effector_add_weights(nullptr);
  particle_settings->pd = BKE_partdeflect_new(PFIELD_NULL);
  particle_settings->pd2 = BKE_partdeflect_new(PFIELD_NULL);
}

static void particle_settings_copy_data(Main * /*bmain*/,
                                        std::optional<Library *> /*owner_library*/,
                                        ID *id_dst,
                                        const ID *id_src,
                                        const int /*flag*/)
{
  ParticleSettings *particle_settings_dst = id_cast<ParticleSettings *>(id_dst);
  const ParticleSettings *partticle_settings_src = id_cast<const ParticleSettings *>(id_src);

  particle_settings_dst->pd = BKE_partdeflect_copy(partticle_settings_src->pd);
  particle_settings_dst->pd2 = BKE_partdeflect_copy(partticle_settings_src->pd2);
  particle_settings_dst->effector_weights = static_cast<EffectorWeights *>(
      MEM_dupalloc(partticle_settings_src->effector_weights));
  particle_settings_dst->fluid = static_cast<SPHFluidSettings *>(
      MEM_dupalloc(partticle_settings_src->fluid));

  if (partticle_settings_src->clumpcurve) {
    particle_settings_dst->clumpcurve = BKE_curvemapping_copy(partticle_settings_src->clumpcurve);
  }
  if (partticle_settings_src->roughcurve) {
    particle_settings_dst->roughcurve = BKE_curvemapping_copy(partticle_settings_src->roughcurve);
  }
  if (partticle_settings_src->twistcurve) {
    particle_settings_dst->twistcurve = BKE_curvemapping_copy(partticle_settings_src->twistcurve);
  }

  particle_settings_dst->boids = boid_copy_settings(partticle_settings_src->boids);

  for (int a = 0; a < MAX_MTEX; a++) {
    if (partticle_settings_src->mtex[a]) {
      particle_settings_dst->mtex[a] = static_cast<MTex *>(
          MEM_dupalloc(partticle_settings_src->mtex[a]));
    }
  }

  BLI_duplicatelist(&particle_settings_dst->instance_weights,
                    &partticle_settings_src->instance_weights);
}

static void particle_settings_free_data(ID *id)
{
  ParticleSettings *particle_settings = id_cast<ParticleSettings *>(id);

  for (int a = 0; a < MAX_MTEX; a++) {
    MEM_SAFE_DELETE(particle_settings->mtex[a]);
  }

  if (particle_settings->clumpcurve) {
    BKE_curvemapping_free(particle_settings->clumpcurve);
  }
  if (particle_settings->roughcurve) {
    BKE_curvemapping_free(particle_settings->roughcurve);
  }
  if (particle_settings->twistcurve) {
    BKE_curvemapping_free(particle_settings->twistcurve);
  }

  BKE_partdeflect_free(particle_settings->pd);
  BKE_partdeflect_free(particle_settings->pd2);

  MEM_SAFE_DELETE(particle_settings->effector_weights);

  particle_settings->instance_weights.free_no_destruct();

  boid_free_settings(particle_settings->boids);
  fluid_free_settings(particle_settings->fluid);
}

static void particle_settings_foreach_id(ID *id, LibraryForeachIDData *data)
{
  ParticleSettings *psett = reinterpret_cast<ParticleSettings *>(id);
  const int flag = BKE_lib_query_foreachid_process_flags_get(data);

  BKE_LIB_FOREACHID_PROCESS_IDSUPER(data, psett->instance_collection, IDWALK_CB_USER);
  BKE_LIB_FOREACHID_PROCESS_IDSUPER(data, psett->instance_object, IDWALK_CB_NOP);
  BKE_LIB_FOREACHID_PROCESS_IDSUPER(data, psett->bb_ob, IDWALK_CB_NOP);
  BKE_LIB_FOREACHID_PROCESS_IDSUPER(data, psett->collision_group, IDWALK_CB_NOP);

  for (int i = 0; i < MAX_MTEX; i++) {
    if (psett->mtex[i]) {
      BKE_LIB_FOREACHID_PROCESS_FUNCTION_CALL(data,
                                              BKE_texture_mtex_foreach_id(data, psett->mtex[i]));
    }
  }

  if (psett->effector_weights) {
    BKE_LIB_FOREACHID_PROCESS_IDSUPER(data, psett->effector_weights->group, IDWALK_CB_USER);
  }

  if (psett->pd) {
    BKE_LIB_FOREACHID_PROCESS_IDSUPER(data, psett->pd->tex, IDWALK_CB_USER);
    BKE_LIB_FOREACHID_PROCESS_IDSUPER(data, psett->pd->f_source, IDWALK_CB_NOP);
  }
  if (psett->pd2) {
    BKE_LIB_FOREACHID_PROCESS_IDSUPER(data, psett->pd2->tex, IDWALK_CB_USER);
    BKE_LIB_FOREACHID_PROCESS_IDSUPER(data, psett->pd2->f_source, IDWALK_CB_NOP);
  }

  if (psett->boids) {
    for (BoidState &state : psett->boids->states) {
      for (BoidRule &rule : state.rules) {
        if (ELEM(rule.type, eBoidRuleType_Avoid, eBoidRuleType_Goal)) {
          BoidRuleGoalAvoid *gabr = reinterpret_cast<BoidRuleGoalAvoid *>(&rule);
          BKE_LIB_FOREACHID_PROCESS_IDSUPER(data, gabr->ob, IDWALK_CB_NOP);
        }
        else if (rule.type == eBoidRuleType_FollowLeader) {
          BoidRuleFollowLeader *flbr = reinterpret_cast<BoidRuleFollowLeader *>(&rule);
          BKE_LIB_FOREACHID_PROCESS_IDSUPER(data, flbr->ob, IDWALK_CB_NOP);
        }
      }
    }
  }

  for (ParticleDupliWeight &dw : psett->instance_weights) {
    BKE_LIB_FOREACHID_PROCESS_IDSUPER(data, dw.ob, IDWALK_CB_NOP);
  }

  if (flag & IDWALK_DO_DEPRECATED_POINTERS) {
    BKE_LIB_FOREACHID_PROCESS_IDSUPER(data, psett->force_group, IDWALK_CB_NOP);
  }
}

static void write_boid_state(BlendWriter *writer, BoidState *state)
{
  writer->write_struct(state);

  for (BoidRule &rule : state->rules) {
    switch (rule.type) {
      case eBoidRuleType_Goal:
      case eBoidRuleType_Avoid:
        writer->write_struct_cast<BoidRuleGoalAvoid>(&rule);
        break;
      case eBoidRuleType_AvoidCollision:
        writer->write_struct_cast<BoidRuleAvoidCollision>(&rule);
        break;
      case eBoidRuleType_FollowLeader:
        writer->write_struct_cast<BoidRuleFollowLeader>(&rule);
        break;
      case eBoidRuleType_AverageSpeed:
        writer->write_struct_cast<BoidRuleAverageSpeed>(&rule);
        break;
      case eBoidRuleType_Fight:
        writer->write_struct_cast<BoidRuleFight>(&rule);
        break;
      default:
        writer->write_struct(&rule);
        break;
    }
  }
#if 0
  BoidCondition *cond = state->conditions.first;
  for (; cond; cond = cond->next) {
    writer->write_struct(cond);
  }
#endif
}

static void particle_settings_blend_write(BlendWriter *writer, ID *id, const void *id_address)
{
  ParticleSettings *part = id_cast<ParticleSettings *>(id);

  /* write LibData */
  writer->write_id_struct(id_address, part);
  BKE_id_blend_write(writer, &part->id);

  writer->write_struct(part->pd);
  writer->write_struct(part->pd2);
  writer->write_struct(part->effector_weights);

  if (part->clumpcurve) {
    BKE_curvemapping_blend_write(writer, part->clumpcurve);
  }
  if (part->roughcurve) {
    BKE_curvemapping_blend_write(writer, part->roughcurve);
  }
  if (part->twistcurve) {
    BKE_curvemapping_blend_write(writer, part->twistcurve);
  }

  for (ParticleDupliWeight &dw : part->instance_weights) {
    /* update indices, but only if dw->ob is set (can be nullptr after loading e.g.) */
    if (dw.ob != nullptr) {
      dw.index = 0;
      if (part->instance_collection) { /* can be nullptr if lining fails or set to None */
        FOREACH_COLLECTION_OBJECT_RECURSIVE_BEGIN (part->instance_collection, object) {
          if (object == dw.ob) {
            break;
          }
          dw.index++;
        }
        FOREACH_COLLECTION_OBJECT_RECURSIVE_END;
      }
    }
    writer->write_struct(&dw);
  }

  if (part->boids && part->phystype == PART_PHYS_BOIDS) {
    writer->write_struct(part->boids);

    for (BoidState &state : part->boids->states) {
      write_boid_state(writer, &state);
    }
  }
  if (part->fluid && part->phystype == PART_PHYS_FLUID) {
    writer->write_struct(part->fluid);
  }

  for (int a = 0; a < MAX_MTEX; a++) {
    if (part->mtex[a]) {
      writer->write_struct(part->mtex[a]);
    }
  }
}

void BKE_particle_partdeflect_blend_read_data(BlendDataReader * /*reader*/, PartDeflect * /*pd*/)
{
}

static void particle_settings_blend_read_data(BlendDataReader *reader, ID *id)
{
  ParticleSettings *part = id_cast<ParticleSettings *>(id);

  BLO_read_struct(reader, PartDeflect, &part->pd);
  BLO_read_struct(reader, PartDeflect, &part->pd2);
  BKE_particle_partdeflect_blend_read_data(reader, part->pd);
  BKE_particle_partdeflect_blend_read_data(reader, part->pd2);

  BLO_read_struct(reader, CurveMapping, &part->clumpcurve);
  if (part->clumpcurve) {
    BKE_curvemapping_blend_read(reader, part->clumpcurve);
  }
  BLO_read_struct(reader, CurveMapping, &part->roughcurve);
  if (part->roughcurve) {
    BKE_curvemapping_blend_read(reader, part->roughcurve);
  }
  BLO_read_struct(reader, CurveMapping, &part->twistcurve);
  if (part->twistcurve) {
    BKE_curvemapping_blend_read(reader, part->twistcurve);
  }

  BLO_read_struct(reader, EffectorWeights, &part->effector_weights);
  if (!part->effector_weights) {
    part->effector_weights = BKE_effector_add_weights(part->force_group);
  }

  BLO_read_struct_list(reader, ParticleDupliWeight, &part->instance_weights);

  BLO_read_struct(reader, BoidSettings, &part->boids);
  BLO_read_struct(reader, SPHFluidSettings, &part->fluid);

  if (part->boids) {
    BLO_read_struct_list(reader, BoidState, &part->boids->states);

    for (BoidState &state : part->boids->states) {
      BLO_read_struct_list(reader, BoidRule, &state.rules);
#if 0
      /* Not implemented yet. */
      BLO_read_struct_list(reader, BoidCondition, &state->conditions);
      BLO_read_struct_list(reader, BoidAction, &state->actions);
#endif
    }
  }
  for (int a = 0; a < MAX_MTEX; a++) {
    BLO_read_struct(reader, MTex, &part->mtex[a]);
  }

  /* Protect against integer overflow vulnerability. */
  CLAMP(part->trail_count, 1, 100000);
}

static void particle_settings_blend_read_after_liblink(BlendLibReader * /*reader*/, ID *id)
{
  ParticleSettings *part = reinterpret_cast<ParticleSettings *>(id);

  if (part->instance_weights.first && !part->instance_collection) {
    part->instance_weights.free_no_destruct();
  }
}

IDTypeInfo IDType_ID_PA = {
    .id_code = ParticleSettings::id_type,
    .id_filter = FILTER_ID_PA,
    .dependencies_id_types = FILTER_ID_OB | FILTER_ID_GR | FILTER_ID_TE,
    .main_listbase_index = INDEX_ID_PA,
    .struct_size = sizeof(ParticleSettings),
    .name = "ParticleSettings",
    .name_plural = N_("particles"),
    .translation_context = BLT_I18NCONTEXT_ID_PARTICLESETTINGS,
    .flags = 0,
    .asset_type_info = nullptr,

    .init_data = particle_settings_init,
    .copy_data = particle_settings_copy_data,
    .free_data = particle_settings_free_data,
    .make_local = nullptr,
    .foreach_id = particle_settings_foreach_id,
    .foreach_cache = nullptr,
    .foreach_path = nullptr,
    .foreach_working_space_color = nullptr,
    .owner_pointer_get = nullptr,

    .blend_write = particle_settings_blend_write,
    .blend_read_data = particle_settings_blend_read_data,
    .blend_read_after_liblink = particle_settings_blend_read_after_liblink,

    .blend_read_undo_preserve = nullptr,

    .lib_override_apply_post = nullptr,
};

uint PSYS_FRAND_SEED_OFFSET[PSYS_FRAND_COUNT];
uint PSYS_FRAND_SEED_MULTIPLIER[PSYS_FRAND_COUNT];
float PSYS_FRAND_BASE[PSYS_FRAND_COUNT];

void BKE_particle_init_rng()
{
  RNG *rng = BLI_rng_new_srandom(5831); /* arbitrary */
  for (int i = 0; i < PSYS_FRAND_COUNT; i++) {
    PSYS_FRAND_BASE[i] = BLI_rng_get_float(rng);
    PSYS_FRAND_SEED_OFFSET[i] = uint(BLI_rng_get_int(rng));
    PSYS_FRAND_SEED_MULTIPLIER[i] = uint(BLI_rng_get_int(rng));
  }
  BLI_rng_free(rng);
}

static void get_child_modifier_parameters(ParticleSettings *part,
                                          ParticleThreadContext *ctx,
                                          ChildParticle *cpa,
                                          short cpa_from,
                                          int cpa_num,
                                          float *cpa_fuv,
                                          float *orco,
                                          ParticleTexture *ptex);
static void get_cpa_texture(Mesh *mesh,
                            ParticleSystem *psys,
                            ParticleSettings *part,
                            ParticleData *par,
                            int child_index,
                            int face_index,
                            const float fw[4],
                            float *orco,
                            ParticleTexture *ptex,
                            int event,
                            float cfra);

int count_particles(ParticleSystem *psys)
{
  ParticleSettings *part = psys->part;
  PARTICLE_P;
  int tot = 0;

  LOOP_SHOWN_PARTICLES
  {
    if (pa->alive == PARS_UNBORN && (part->flag & PART_UNBORN) == 0) {
    }
    else if (pa->alive == PARS_DEAD && (part->flag & PART_DIED) == 0) {
    }
    else {
      tot++;
    }
  }
  return tot;
}
int count_particles_mod(ParticleSystem *psys, int totgr, int cur)
{
  ParticleSettings *part = psys->part;
  PARTICLE_P;
  int tot = 0;

  LOOP_SHOWN_PARTICLES
  {
    if (pa->alive == PARS_UNBORN && (part->flag & PART_UNBORN) == 0) {
    }
    else if (pa->alive == PARS_DEAD && (part->flag & PART_DIED) == 0) {
    }
    else if (p % totgr == cur) {
      tot++;
    }
  }
  return tot;
}
/* We allocate path cache memory in chunks instead of a big contiguous
 * chunk, windows' memory allocator fails to find big blocks of memory often. */

#define PATH_CACHE_BUF_SIZE 1024

static ParticleCacheKey *pcache_key_segment_endpoint_safe(ParticleCacheKey *key)
{
  return (key->segments > 0) ? (key + (key->segments - 1)) : key;
}

static ParticleCacheKey **psys_alloc_path_cache_buffers(ListBaseT<LinkData> *bufs,
                                                        int tot,
                                                        int totkeys)
{
  LinkData *buf;
  ParticleCacheKey **cache;
  int i, totkey, totbufkey;

  tot = std::max(tot, 1);
  totkey = 0;
  cache = MEM_new_array_zeroed<ParticleCacheKey *>(tot, "PathCacheArray");

  while (totkey < tot) {
    totbufkey = std::min(tot - totkey, PATH_CACHE_BUF_SIZE);
    buf = MEM_new_zeroed<LinkData>("PathCacheLinkData");
    buf->data = MEM_new_array_zeroed<ParticleCacheKey>(size_t(totbufkey) * size_t(totkeys),
                                                       "ParticleCacheKey");

    for (i = 0; i < totbufkey; i++) {
      cache[totkey + i] = (static_cast<ParticleCacheKey *>(buf->data)) + i * totkeys;
    }

    totkey += totbufkey;
    BLI_addtail(bufs, buf);
  }

  return cache;
}

static void psys_free_path_cache_buffers(ParticleCacheKey **cache, ListBaseT<LinkData> *bufs)
{
  if (cache) {
    MEM_delete(cache);
  }

  for (LinkData &buf : *bufs) {
    MEM_delete(static_cast<ParticleCacheKey *>(buf.data));
  }
  bufs->free_no_destruct();
}

/* -------------------------------------------------------------------- */
/** \name Getting Stuff
 * \{ */

ParticleSystem *psys_get_current(Object *ob)
{
  if (ob == nullptr) {
    return nullptr;
  }

  for (ParticleSystem &psys : ob->particlesystem) {
    if (psys.flag & PSYS_CURRENT) {
      return &psys;
    }
  }

  return nullptr;
}
short psys_get_current_num(Object *ob)
{
  ParticleSystem *psys;
  short i;

  if (ob == nullptr) {
    return 0;
  }

  for (psys = static_cast<ParticleSystem *>(ob->particlesystem.first), i = 0; psys;
       psys = psys->next, i++)
  {
    if (psys->flag & PSYS_CURRENT) {
      return i;
    }
  }

  return i;
}
void psys_set_current_num(Object *ob, int index)
{
  ParticleSystem *psys;
  short i;

  if (ob == nullptr) {
    return;
  }

  for (psys = static_cast<ParticleSystem *>(ob->particlesystem.first), i = 0; psys;
       psys = psys->next, i++)
  {
    if (i == index) {
      psys->flag |= PSYS_CURRENT;
    }
    else {
      psys->flag &= ~PSYS_CURRENT;
    }
  }
}

void psys_sim_data_init(ParticleSimulationData *sim)
{
  ParticleSystem *psys = sim->psys;
  ParticleSettings *part = psys->part;

  /* Prepare lattice deform. */
  psys->lattice_deform_data = nullptr;
  if (psys_in_edit_mode(sim->depsgraph, sim->psys) == 0) {
    Object *lattice = nullptr;
    ModifierData *md = reinterpret_cast<ModifierData *>(psys_get_modifier(sim->ob, sim->psys));
    bool for_render = DEG_get_mode(sim->depsgraph) == DAG_EVAL_RENDER;
    int mode = for_render ? eModifierMode_Render : eModifierMode_Realtime;

    for (; md; md = md->next) {
      if (md->type == eModifierType_Lattice) {
        if (md->mode & mode) {
          LatticeModifierData *lmd = reinterpret_cast<LatticeModifierData *>(md);
          lattice = lmd->object;
          psys->lattice_strength = lmd->strength;
        }

        break;
      }
    }
    if (lattice && lattice->type == OB_LATTICE) {
      psys->lattice_deform_data = BKE_lattice_deform_data_create(lattice, nullptr);
    }
  }

  /* Prepare curvemapping tables. */
  if ((part->child_flag & PART_CHILD_USE_CLUMP_CURVE) && part->clumpcurve) {
    BKE_curvemapping_init(part->clumpcurve);
  }
  if ((part->child_flag & PART_CHILD_USE_ROUGH_CURVE) && part->roughcurve) {
    BKE_curvemapping_init(part->roughcurve);
  }
  if ((part->child_flag & PART_CHILD_USE_TWIST_CURVE) && part->twistcurve) {
    BKE_curvemapping_init(part->twistcurve);
  }
}

void psys_sim_data_free(ParticleSimulationData *sim)
{
  ParticleSystem *psys = sim->psys;

  if (psys->lattice_deform_data) {
    BKE_lattice_deform_data_destroy(psys->lattice_deform_data);
    psys->lattice_deform_data = nullptr;
  }
}

void psys_disable_all(Object *ob)
{
  ParticleSystem *psys = static_cast<ParticleSystem *>(ob->particlesystem.first);

  for (; psys; psys = psys->next) {
    psys->flag |= PSYS_DISABLED;
  }
}
void psys_enable_all(Object *ob)
{
  ParticleSystem *psys = static_cast<ParticleSystem *>(ob->particlesystem.first);

  for (; psys; psys = psys->next) {
    psys->flag &= ~PSYS_DISABLED;
  }
}

ParticleSystem *psys_orig_get(ParticleSystem *psys)
{
  if (psys->orig_psys == nullptr) {
    return psys;
  }
  return psys->orig_psys;
}

ParticleSystem *psys_eval_get(Depsgraph *depsgraph, Object *object, ParticleSystem *psys)
{
  Object *object_eval = DEG_get_evaluated(depsgraph, object);
  if (object_eval == object) {
    return psys;
  }
  ParticleSystem *psys_eval = static_cast<ParticleSystem *>(object_eval->particlesystem.first);
  while (psys_eval != nullptr) {
    if (psys_eval->orig_psys == psys) {
      return psys_eval;
    }
    psys_eval = psys_eval->next;
  }
  return psys_eval;
}

static PTCacheEdit *psys_orig_edit_get(ParticleSystem *psys)
{
  if (psys->orig_psys == nullptr) {
    return psys->edit;
  }
  return psys->orig_psys->edit;
}

bool psys_in_edit_mode(Depsgraph *depsgraph, const ParticleSystem *psys)
{
  const Scene *scene = DEG_get_input_scene(depsgraph);
  ViewLayer *view_layer = DEG_get_input_view_layer(depsgraph);
  BKE_view_layer_synced_ensure(*DEG_get_bmain(depsgraph), scene, view_layer);
  const Object *object = BKE_view_layer_active_object_get(view_layer);
  if (object == nullptr) {
    /* TODO(sergey): Needs double-check with multi-object edit. */
    return false;
  }
  const bool use_render_params = (DEG_get_mode(depsgraph) == DAG_EVAL_RENDER);
  if (object->mode != OB_MODE_PARTICLE_EDIT) {
    return false;
  }
  const ParticleSystem *psys_orig = psys_orig_get(const_cast<ParticleSystem *>(psys));
  return (psys_orig->edit || psys->pointcache->edit) && (use_render_params == false);
}

bool psys_check_enabled(Object *ob, ParticleSystem *psys, const bool use_render_params)
{
  ParticleSystemModifierData *psmd;

  if (psys->flag & PSYS_DISABLED || psys->flag & PSYS_DELETE || !psys->part) {
    return false;
  }

  psmd = psys_get_modifier(ob, psys);

  if (!psmd) {
    return false;
  }

  if (use_render_params) {
    if (!(psmd->modifier.mode & eModifierMode_Render)) {
      return false;
    }
  }
  else if (!(psmd->modifier.mode & eModifierMode_Realtime)) {
    return false;
  }

  return true;
}

bool psys_check_edited(ParticleSystem *psys)
{
  if (psys->part && psys->part->type == PART_HAIR) {
    return (psys->flag & PSYS_EDITED || (psys->edit && psys->edit->edited));
  }

  return (psys->pointcache->edit && psys->pointcache->edit->edited);
}

void psys_find_group_weights(ParticleSettings *part)
{
  /* Find object pointers based on index. If the collection is linked from
   * another library linking may not have the object pointers available on
   * file load, so we have to retrieve them later. See #49273. */
  ListBaseT<Base> instance_collection_objects = {nullptr, nullptr};

  if (part->instance_collection) {
    instance_collection_objects = BKE_collection_object_cache_get(part->instance_collection);
  }

  for (ParticleDupliWeight &dw : part->instance_weights) {
    if (dw.ob == nullptr) {
      Base *base = static_cast<Base *>(BLI_findlink(&instance_collection_objects, dw.index));
      if (base != nullptr) {
        dw.ob = base->object;
      }
    }
  }
}

void psys_check_group_weights(ParticleSettings *part)
{
  ParticleDupliWeight *dw, *tdw;

  if (part->ren_as != PART_DRAW_GR || !part->instance_collection) {
    part->instance_weights.free_no_destruct();
    return;
  }

  /* Find object pointers. */
  psys_find_group_weights(part);

  /* Remove nullptr objects, that were removed from the collection. */
  dw = static_cast<ParticleDupliWeight *>(part->instance_weights.first);
  while (dw) {
    if (dw->ob == nullptr ||
        !BKE_collection_has_object_recursive(part->instance_collection, dw->ob))
    {
      tdw = dw->next;
      BLI_freelinkN(&part->instance_weights, dw);
      dw = tdw;
    }
    else {
      dw = dw->next;
    }
  }

  /* Add new objects in the collection. */
  int index = 0;
  FOREACH_COLLECTION_OBJECT_RECURSIVE_BEGIN (part->instance_collection, object) {
    dw = static_cast<ParticleDupliWeight *>(part->instance_weights.first);
    while (dw && dw->ob != object) {
      dw = dw->next;
    }

    if (!dw) {
      dw = MEM_new<ParticleDupliWeight>("ParticleDupliWeight");
      dw->ob = object;
      dw->count = 1;
      BLI_addtail(&part->instance_weights, dw);
    }

    dw->index = index++;
  }
  FOREACH_COLLECTION_OBJECT_RECURSIVE_END;

  /* Ensure there is an element marked as current. */
  int current = 0;
  for (ParticleDupliWeight &dw : part->instance_weights) {
    if (dw.flag & PART_DUPLIW_CURRENT) {
      current = 1;
      break;
    }
  }

  if (!current) {
    dw = static_cast<ParticleDupliWeight *>(part->instance_weights.first);
    if (dw) {
      dw->flag |= PART_DUPLIW_CURRENT;
    }
  }
}

int psys_uses_gravity(ParticleSimulationData *sim)
{
  return sim->scene->physics_settings.flag & PHYS_GLOBAL_GRAVITY && sim->psys->part &&
         sim->psys->part->effector_weights->global_gravity != 0.0f;
}

/** \} */

/* -------------------------------------------------------------------- */
/** \name Freeing Stuff
 * \{ */

static void fluid_free_settings(SPHFluidSettings *fluid)
{
  if (fluid) {
    MEM_delete(fluid);
  }
}

void free_hair(Object *object, ParticleSystem *psys, int dynamics)
{
  PARTICLE_P;

  LOOP_PARTICLES
  {
    MEM_SAFE_DELETE(pa->hair);
    pa->totkey = 0;
  }

  psys->flag &= ~PSYS_HAIR_DONE;

  if (psys->clmd) {
    if (dynamics) {
      BKE_modifier_free(reinterpret_cast<ModifierData *>(psys->clmd));
      psys->clmd = nullptr;
      PTCacheID pid;
      BKE_ptcache_id_from_particles(&pid, object, psys);
      BKE_ptcache_id_clear(&pid, PTCACHE_CLEAR_ALL, 0);
    }
    else {
      cloth_free_modifier(psys->clmd);
    }
  }

  if (psys->hair_in_mesh) {
    BKE_id_free(nullptr, psys->hair_in_mesh);
  }
  psys->hair_in_mesh = nullptr;

  if (psys->hair_out_mesh) {
    BKE_id_free(nullptr, psys->hair_out_mesh);
  }
  psys->hair_out_mesh = nullptr;
}
void free_keyed_keys(ParticleSystem *psys)
{
  PARTICLE_P;

  if (psys->part->type == PART_HAIR) {
    return;
  }

  if (psys->particles && psys->particles->keys) {
    MEM_delete(psys->particles->keys);

    LOOP_PARTICLES
    {
      if (pa->keys) {
        pa->keys = nullptr;
        pa->totkey = 0;
      }
    }
  }
}
static void free_child_path_cache(ParticleSystem *psys)
{
  psys_free_path_cache_buffers(psys->childcache, &psys->childcachebufs);
  psys->childcache = nullptr;
  psys->totchildcache = 0;
}
void psys_free_path_cache(ParticleSystem *psys, PTCacheEdit *edit)
{
  if (edit) {
    psys_free_path_cache_buffers(edit->pathcache, &edit->pathcachebufs);
    edit->pathcache = nullptr;
    edit->totcached = 0;
  }
  if (psys) {
    psys_free_path_cache_buffers(psys->pathcache, &psys->pathcachebufs);
    psys->pathcache = nullptr;
    psys->totcached = 0;

    free_child_path_cache(psys);
  }
}
void psys_free_children(ParticleSystem *psys)
{
  if (psys->child) {
    MEM_delete(psys->child);
    psys->child = nullptr;
    psys->totchild = 0;
  }

  free_child_path_cache(psys);
}
void psys_free_particles(ParticleSystem *psys)
{
  PARTICLE_P;

  if (psys->particles) {
    /* Even though psys->part should never be nullptr,
     * this can happen as an exception during deletion.
     * See ID_REMAP_SKIP/FORCE/FLAG_NEVER_NULL_USAGE in BKE_library_remap. */
    if (psys->part && psys->part->type == PART_HAIR) {
      LOOP_PARTICLES
      {
        if (pa->hair) {
          MEM_delete(pa->hair);
        }
      }
    }

    if (psys->particles->keys) {
      MEM_delete(psys->particles->keys);
    }

    if (psys->particles->boid) {
      MEM_delete(psys->particles->boid);
    }

    MEM_delete(psys->particles);
    psys->particles = nullptr;
    psys->totpart = 0;
  }
}
void psys_free_pdd(ParticleSystem *psys)
{
  if (psys->pdd) {
    MEM_SAFE_DELETE(psys->pdd->cdata);

    MEM_SAFE_DELETE(psys->pdd->vdata);

    MEM_SAFE_DELETE(psys->pdd->ndata);

    MEM_SAFE_DELETE(psys->pdd->vedata);

    psys->pdd->totpoint = 0;
    psys->pdd->totpart = 0;
    psys->pdd->partsize = 0;
  }
}
void psys_free(Object *ob, ParticleSystem *psys)
{
  if (psys) {
    int nr = 0;

    psys_free_path_cache(psys, nullptr);

    /* NOTE: We pass dynamics=0 to free_hair() to prevent it from doing an
     * unneeded clear of the cache. But for historical reason that code path
     * was only clearing cloth part of modifier data.
     *
     * Part of the story there is that particle evaluation is trying to not
     * re-allocate thew ModifierData itself, and limits all allocations to
     * the cloth part of it.
     *
     * Why evaluation is relying on hair_free() and in some specific code
     * paths there is beyond me.
     */
    free_hair(ob, psys, 0);
    if (psys->clmd != nullptr) {
      BKE_modifier_free(reinterpret_cast<ModifierData *>(psys->clmd));
    }

    psys_free_particles(psys);

    if (psys->edit && psys->free_edit) {
      psys->free_edit(psys->edit);
    }

    if (psys->child) {
      MEM_delete(psys->child);
      psys->child = nullptr;
      psys->totchild = 0;
    }

    /* check if we are last non-visible particle system */
    for (ParticleSystem &tpsys : ob->particlesystem) {
      if (tpsys.part) {
        if (ELEM(tpsys.part->ren_as, PART_DRAW_OB, PART_DRAW_GR)) {
          nr++;
          break;
        }
      }
    }
    /* clear do-not-draw-flag */
    if (!nr) {
      ob->transflag &= ~OB_DUPLIPARTS;
    }

    psys->part = nullptr;

    if ((psys->flag & PSYS_SHARED_CACHES) == 0) {
      BKE_ptcache_free_list(&psys->ptcaches);
    }
    psys->pointcache = nullptr;

    psys->targets.free_no_destruct();

    BLI_bvhtree_free(psys->bvhtree);
    kdtree_free<float3>(psys->tree);

    if (psys->fluid_springs) {
      MEM_delete(psys->fluid_springs);
    }

    BKE_effectors_free(psys->effectors);

    if (psys->pdd) {
      psys_free_pdd(psys);
      MEM_delete(psys->pdd);
    }

    BKE_particle_batch_cache_free(psys);

    MEM_delete(psys);
  }
}

void psys_copy_particles(ParticleSystem *psys_dst, ParticleSystem *psys_src)
{
  /* Free existing particles. */
  if (psys_dst->particles != psys_src->particles) {
    psys_free_particles(psys_dst);
  }
  if (psys_dst->child != psys_src->child) {
    psys_free_children(psys_dst);
  }
  /* Restore counters. */
  psys_dst->totpart = psys_src->totpart;
  psys_dst->totchild = psys_src->totchild;
  /* Copy particles and children. */
  psys_dst->particles = MEM_dupalloc(psys_src->particles);
  psys_dst->child = MEM_dupalloc(psys_src->child);

  /* Ideally this should only be performed if `(psys_dst->part->type == PART_HAIR)`.
   *
   * But #ParticleData (`psys_dst`) is some sub-data of the #Object ID, while #ParticleSettings
   * (`psys_dst->part`) is another ID. In case the particle settings is a linked ID that gets
   * missing, it will be replaced (in readfile code) by a place-holder, which defaults to a
   * `PART_EMITTER` type of particle settings.
   *
   * This leads to a situation where each particle of `psys_dst` still has a valid allocated `hair`
   * data, which should still be preserved in case the missing particle settings ID becomes valid
   * again.
   *
   * Furthermore, #free_hair() always frees `pa->hair` if it's not nullptr, regardless of the
   * particle type. So *not* copying here would cause a double free (or more), e.g. freeing the
   * copy-on-evaluation copy and the original data will crash Blender.
   * In any case, sharing pointers between `psys_src` and `psys_dst` should be forbidden.
   *
   * So while we could in theory 'sanitize' the situation by setting `pa->hair` to nullptr in the
   * new copy (in case of non-`PART_HAIR` type), it is probably safer for now to systematically
   * duplicate the `hair` data if available. */
  {
    ParticleData *pa;
    int p;
    for (p = 0, pa = psys_dst->particles; p < psys_dst->totpart; p++, pa++) {
      pa->hair = MEM_dupalloc(pa->hair);
    }
  }
  if (psys_dst->particles && (psys_dst->particles->keys || psys_dst->particles->boid)) {
    ParticleKey *key = psys_dst->particles->keys;
    BoidParticle *boid = psys_dst->particles->boid;
    ParticleData *pa;
    int p;
    if (key != nullptr) {
      key = MEM_dupalloc(key);
    }
    if (boid != nullptr) {
      boid = MEM_dupalloc(boid);
    }
    for (p = 0, pa = psys_dst->particles; p < psys_dst->totpart; p++, pa++) {
      if (boid != nullptr) {
        pa->boid = boid++;
      }
      if (key != nullptr) {
        pa->keys = key;
        key += pa->totkey;
      }
    }
  }
}

/** \} */

/* -------------------------------------------------------------------- */
/** \name Interpolation
 * \{ */

static float interpolate_particle_value(
    float v1, float v2, float v3, float v4, const float w[4], int four)
{
  float value;

  value = w[0] * v1 + w[1] * v2 + w[2] * v3;
  if (four) {
    value += w[3] * v4;
  }

  CLAMP(value, 0.0f, 1.0f);

  return value;
}

void psys_interpolate_particle(
    short type, ParticleKey keys[4], float dt, ParticleKey *result, bool velocity)
{
  float t[4];

  if (type < 0) {
    interp_cubic_v3(result->co, result->vel, keys[1].co, keys[1].vel, keys[2].co, keys[2].vel, dt);
  }
  else {
    key_curve_position_weights(dt, t, KeyInterpolationType(type));

    interp_v3_v3v3v3v3(result->co, keys[0].co, keys[1].co, keys[2].co, keys[3].co, t);

    if (velocity) {
      float temp[3];

      if (dt > 0.999f) {
        key_curve_position_weights(dt - 0.001f, t, KeyInterpolationType(type));
        interp_v3_v3v3v3v3(temp, keys[0].co, keys[1].co, keys[2].co, keys[3].co, t);
        sub_v3_v3v3(result->vel, result->co, temp);
      }
      else {
        key_curve_position_weights(dt + 0.001f, t, KeyInterpolationType(type));
        interp_v3_v3v3v3v3(temp, keys[0].co, keys[1].co, keys[2].co, keys[3].co, t);
        sub_v3_v3v3(result->vel, temp, result->co);
      }
    }
  }
}

struct ParticleInterpolationData {
  HairKey *hkey[2];

  Mesh *mesh;
  float3 *vert_positions[2];

  int keyed;
  ParticleKey *kkey[2];

  PointCache *cache;
  PTCacheMem *pm;

  PTCacheEditPoint *epoint;
  PTCacheEditKey *ekey[2];

  float birthtime;
  /** Die on this frame, see #ParticleData.dietime for details. */
  float dietime;
  int bspline;
};
/**
 * Assumes pointcache->mem_cache exists, so for disk cached particles
 * call #psys_make_temp_pointcache() before use.
 * It uses #ParticleInterpolationData.pm to store the current memory cache frame
 * so it's thread safe.
 */
static void get_pointcache_keys_for_time(Object * /*ob*/,
                                         PointCache *cache,
                                         PTCacheMem **cur,
                                         int index,
                                         float t,
                                         ParticleKey *key1,
                                         ParticleKey *key2)
{
  static PTCacheMem *pm = nullptr;
  int index1, index2;

  if (index < 0) { /* initialize */
    *cur = static_cast<PTCacheMem *>(cache->mem_cache.first);

    if (*cur) {
      *cur = (*cur)->next;
    }
  }
  else {
    if (*cur) {
      while (*cur && (*cur)->next && float((*cur)->frame) < t) {
        *cur = (*cur)->next;
      }

      pm = *cur;

      index2 = BKE_ptcache_mem_index_find(pm, index);
      index1 = BKE_ptcache_mem_index_find(pm->prev, index);
      if (index2 < 0) {
        return;
      }

      BKE_ptcache_make_particle_key(key2, index2, pm->data, float(pm->frame));
      if (index1 < 0) {
        copy_particle_key(key1, key2, 1);
      }
      else {
        BKE_ptcache_make_particle_key(key1, index1, pm->prev->data, float(pm->prev->frame));
      }
    }
    else if (cache->mem_cache.first) {
      pm = static_cast<PTCacheMem *>(cache->mem_cache.first);
      index2 = BKE_ptcache_mem_index_find(pm, index);
      if (index2 < 0) {
        return;
      }
      BKE_ptcache_make_particle_key(key2, index2, pm->data, float(pm->frame));
      copy_particle_key(key1, key2, 1);
    }
  }
}
static int get_pointcache_times_for_particle(PointCache *cache,
                                             int index,
                                             float *r_start,
                                             float *r_dietime)
{
  int ret = 0;

  for (PTCacheMem &pm : cache->mem_cache) {
    if (BKE_ptcache_mem_index_find(&pm, index) >= 0) {
      *r_start = pm.frame;
      ret++;
      break;
    }
  }

  for (PTCacheMem &pm : cache->mem_cache.items_reversed()) {
    if (BKE_ptcache_mem_index_find(&pm, index) >= 0) {
      /* Die *after* the last available frame. */
      *r_dietime = pm.frame + 1;
      ret++;
      break;
    }
  }

  return ret == 2;
}

float psys_get_dietime_from_cache(PointCache *cache, int index)
{
  int dietime = 10000000; /* some max value so that we can default to pa->time+lifetime */

  for (PTCacheMem &pm : cache->mem_cache.items_reversed()) {
    if (BKE_ptcache_mem_index_find(&pm, index) >= 0) {
      /* Die *after* the last available frame. */
      dietime = pm.frame + 1;
      break;
    }
  }

  return float(dietime);
}

static void init_particle_interpolation(Object *ob,
                                        ParticleSystem *psys,
                                        ParticleData *pa,
                                        ParticleInterpolationData *pind)
{

  if (pind->epoint) {
    PTCacheEditPoint *point = pind->epoint;

    pind->ekey[0] = point->keys;
    pind->ekey[1] = point->totkey > 1 ? point->keys + 1 : nullptr;

    pind->birthtime = *(point->keys->time);
    pind->dietime = *((point->keys + point->totkey - 1)->time);
  }
  else if (pind->keyed) {
    ParticleKey *key = pa->keys;
    pind->kkey[0] = key;
    pind->kkey[1] = pa->totkey > 1 ? key + 1 : nullptr;

    pind->birthtime = key->time;
    pind->dietime = (key + pa->totkey - 1)->time;
  }
  else if (pind->cache) {
    float start = 0.0f, dietime = 0.0f;
    get_pointcache_keys_for_time(ob, pind->cache, &pind->pm, -1, 0.0f, nullptr, nullptr);
    pind->birthtime = pa ? pa->time : pind->cache->startframe;
    pind->dietime = pa ? pa->dietime : (pind->cache->endframe + 1);

    if (get_pointcache_times_for_particle(pind->cache, pa - psys->particles, &start, &dietime)) {
      pind->birthtime = std::max(pind->birthtime, start);
      pind->dietime = std::min(pind->dietime, dietime);
    }
  }
  else {
    HairKey *key = pa->hair;
    pind->hkey[0] = key;
    pind->hkey[1] = key + 1;

    pind->birthtime = key->time;
    pind->dietime = (key + pa->totkey - 1)->time;

    if (pind->mesh) {
      float3 *positions = pind->mesh->vert_positions_for_write().data();
      pind->vert_positions[0] = &positions[pa->hair_index];
      pind->vert_positions[1] = pind->vert_positions[0] + 1;
    }
  }
}
static void edit_to_particle(ParticleKey *key, PTCacheEditKey *ekey)
{
  copy_v3_v3(key->co, ekey->co);
  if (ekey->vel) {
    copy_v3_v3(key->vel, ekey->vel);
  }
  key->time = *(ekey->time);
}
static void hair_to_particle(ParticleKey *key, HairKey *hkey)
{
  copy_v3_v3(key->co, hkey->co);
  key->time = hkey->time;
}

static void mvert_to_particle(ParticleKey *key, float3 *position, HairKey *hkey)
{
  copy_v3_v3(key->co, *position);
  key->time = hkey->time;
}

static void do_particle_interpolation(ParticleSystem *psys,
                                      int p,
                                      ParticleData *pa,
                                      float t,
                                      ParticleInterpolationData *pind,
                                      ParticleKey *result)
{
  PTCacheEditPoint *point = pind->epoint;
  int point_vel = (point && point->keys->vel);
  float real_t, dfra, keytime, invdt = 1.0f;

  /* billboards won't fill in all of these, so start cleared */
  ParticleKey keys[4] = {};

  /* interpret timing and find keys */
  if (point) {
    if (result->time < 0.0f) {
      real_t = -result->time;
    }
    else {
      real_t = *(pind->ekey[0]->time) +
               t * (*(pind->ekey[0][point->totkey - 1].time) - *(pind->ekey[0]->time));
    }

    while (*(pind->ekey[1]->time) < real_t) {
      pind->ekey[1]++;
    }

    pind->ekey[0] = pind->ekey[1] - 1;
  }
  else if (pind->keyed) {
    /* we have only one key, so let's use that */
    if (pind->kkey[1] == nullptr) {
      copy_particle_key(result, pind->kkey[0], 1);
      return;
    }

    if (result->time < 0.0f) {
      real_t = -result->time;
    }
    else {
      real_t = pind->kkey[0]->time +
               t * (pind->kkey[0][pa->totkey - 1].time - pind->kkey[0]->time);
    }

    if (psys->part->phystype == PART_PHYS_KEYED && psys->flag & PSYS_KEYED_TIMING) {
      ParticleTarget *pt = static_cast<ParticleTarget *>(psys->targets.first);

      pt = pt->next;

      while (pt && pa->time + pt->time < real_t) {
        pt = pt->next;
      }

      if (pt) {
        pt = pt->prev;

        if (pa->time + pt->time + pt->duration > real_t) {
          real_t = pa->time + pt->time;
        }
      }
      else {
        real_t = pa->time + (static_cast<ParticleTarget *>(psys->targets.last))->time;
      }
    }

    CLAMP(real_t, pa->time, pa->dietime);

    while (pind->kkey[1]->time < real_t) {
      pind->kkey[1]++;
    }

    pind->kkey[0] = pind->kkey[1] - 1;
  }
  else if (pind->cache) {
    if (result->time < 0.0f) { /* flag for time in frames */
      real_t = -result->time;
    }
    else {
      real_t = pa->time + t * (pa->dietime - pa->time);
    }
  }
  else {
    if (result->time < 0.0f) {
      real_t = -result->time;
    }
    else {
      real_t = pind->hkey[0]->time +
               t * (pind->hkey[0][pa->totkey - 1].time - pind->hkey[0]->time);
    }

    while (pind->hkey[1]->time < real_t) {
      pind->hkey[1]++;
      if (pind->mesh) {
        pind->vert_positions[1]++;
      }
    }

    pind->hkey[0] = pind->hkey[1] - 1;
  }

  /* set actual interpolation keys */
  if (point) {
    edit_to_particle(keys + 1, pind->ekey[0]);
    edit_to_particle(keys + 2, pind->ekey[1]);
  }
  else if (pind->mesh) {
    pind->vert_positions[0] = pind->vert_positions[1] - 1;
    mvert_to_particle(keys + 1, pind->vert_positions[0], pind->hkey[0]);
    mvert_to_particle(keys + 2, pind->vert_positions[1], pind->hkey[1]);
  }
  else if (pind->keyed) {
    memcpy(keys + 1, pind->kkey[0], sizeof(ParticleKey));
    memcpy(keys + 2, pind->kkey[1], sizeof(ParticleKey));
  }
  else if (pind->cache) {
    get_pointcache_keys_for_time(nullptr, pind->cache, &pind->pm, p, real_t, keys + 1, keys + 2);
  }
  else {
    hair_to_particle(keys + 1, pind->hkey[0]);
    hair_to_particle(keys + 2, pind->hkey[1]);
  }

  /* set secondary interpolation keys for hair */
  if (!pind->keyed && !pind->cache && !point_vel) {
    if (point) {
      if (pind->ekey[0] != point->keys) {
        edit_to_particle(keys, pind->ekey[0] - 1);
      }
      else {
        edit_to_particle(keys, pind->ekey[0]);
      }
    }
    else if (pind->mesh) {
      if (pind->hkey[0] != pa->hair) {
        mvert_to_particle(keys, pind->vert_positions[0] - 1, pind->hkey[0] - 1);
      }
      else {
        mvert_to_particle(keys, pind->vert_positions[0], pind->hkey[0]);
      }
    }
    else {
      if (pind->hkey[0] != pa->hair) {
        hair_to_particle(keys, pind->hkey[0] - 1);
      }
      else {
        hair_to_particle(keys, pind->hkey[0]);
      }
    }

    if (point) {
      if (pind->ekey[1] != point->keys + point->totkey - 1) {
        edit_to_particle(keys + 3, pind->ekey[1] + 1);
      }
      else {
        edit_to_particle(keys + 3, pind->ekey[1]);
      }
    }
    else if (pind->mesh) {
      if (pind->hkey[1] != pa->hair + pa->totkey - 1) {
        mvert_to_particle(keys + 3, pind->vert_positions[1] + 1, pind->hkey[1] + 1);
      }
      else {
        mvert_to_particle(keys + 3, pind->vert_positions[1], pind->hkey[1]);
      }
    }
    else {
      if (pind->hkey[1] != pa->hair + pa->totkey - 1) {
        hair_to_particle(keys + 3, pind->hkey[1] + 1);
      }
      else {
        hair_to_particle(keys + 3, pind->hkey[1]);
      }
    }
  }

  dfra = keys[2].time - keys[1].time;
  keytime = (real_t - keys[1].time) / dfra;

  /* Convert velocity to time-step size. */
  if (pind->keyed || pind->cache || point_vel) {
    invdt = dfra * 0.04f * (psys ? psys->part->timetweak : 1.0f);
    mul_v3_fl(keys[1].vel, invdt);
    mul_v3_fl(keys[2].vel, invdt);
    interp_qt_qtqt(result->rot, keys[1].rot, keys[2].rot, keytime);
  }

  /* Now we should have in chronological order k1<=k2<=t<=k3<=k4 with key-time between
   * [0, 1]->[k2, k3] (k1 & k4 used for cardinal & b-spline interpolation). */
  psys_interpolate_particle((pind->keyed || pind->cache || point_vel) ?
                                -1 /* signal for cubic interpolation */
                                :
                                (pind->bspline ? KEY_BSPLINE : KEY_CARDINAL),
                            keys,
                            keytime,
                            result,
                            true);

  /* the velocity needs to be converted back from cubic interpolation */
  if (pind->keyed || pind->cache || point_vel) {
    mul_v3_fl(result->vel, 1.0f / invdt);
  }
}

static void interpolate_pathcache(ParticleCacheKey *first, float t, ParticleCacheKey *result)
{
  int i = 0;
  ParticleCacheKey *cur = first;

  /* scale the requested time to fit the entire path even if the path is cut early */
  t *= (first + first->segments)->time;

  while (i < first->segments && cur->time < t) {
    cur++;
  }

  if (cur->time == t) {
    *result = *cur;
  }
  else {
    float dt = (t - (cur - 1)->time) / (cur->time - (cur - 1)->time);
    interp_v3_v3v3(result->co, (cur - 1)->co, cur->co, dt);
    interp_v3_v3v3(result->vel, (cur - 1)->vel, cur->vel, dt);
    interp_qt_qtqt(result->rot, (cur - 1)->rot, cur->rot, dt);
    result->time = t;
  }

  /* first is actual base rotation, others are incremental from first */
  if (cur == first || cur - 1 == first) {
    copy_qt_qt(result->rot, first->rot);
  }
  else {
    mul_qt_qtqt(result->rot, first->rot, result->rot);
  }
}

/** \} */

/* -------------------------------------------------------------------- */
/** \name Particles on a DM
 * \{ */

void psys_interpolate_face(Mesh *mesh,
                           const float (*vert_positions)[3],
                           const float (*vert_normals)[3],
                           const MFace *mface,
                           MTFace *tface,
                           const float (*orcodata)[3],
                           float w[4],
                           float vec[3],
                           float nor[3],
                           float utan[3],
                           float vtan[3],
                           float orco[3])
{
  const float *v1 = nullptr, *v2 = nullptr, *v3 = nullptr, *v4 = nullptr;
  float e1[3], e2[3], s1, s2, t1, t2;
  float *uv1, *uv2, *uv3, *uv4;
  float n1[3], n2[3], n3[3], n4[3];
  float tuv[4][2];
  const float *o1, *o2, *o3, *o4;

  v1 = vert_positions[mface->v1];
  v2 = vert_positions[mface->v2];
  v3 = vert_positions[mface->v3];

  copy_v3_v3(n1, vert_normals[mface->v1]);
  copy_v3_v3(n2, vert_normals[mface->v2]);
  copy_v3_v3(n3, vert_normals[mface->v3]);

  if (mface->v4) {
    v4 = vert_positions[mface->v4];
    copy_v3_v3(n4, vert_normals[mface->v4]);

    interp_v3_v3v3v3v3(vec, v1, v2, v3, v4, w);

    if (nor) {
      if (mface->flag & ME_SMOOTH) {
        interp_v3_v3v3v3v3(nor, n1, n2, n3, n4, w);
      }
      else {
        normal_quad_v3(nor, v1, v2, v3, v4);
      }
    }
  }
  else {
    interp_v3_v3v3v3(vec, v1, v2, v3, w);

    if (nor) {
      if (mface->flag & ME_SMOOTH) {
        interp_v3_v3v3v3(nor, n1, n2, n3, w);
      }
      else {
        normal_tri_v3(nor, v1, v2, v3);
      }
    }
  }

  /* calculate tangent vectors */
  if (utan && vtan) {
    if (tface) {
      uv1 = tface->uv[0];
      uv2 = tface->uv[1];
      uv3 = tface->uv[2];
      uv4 = tface->uv[3];
    }
    else {
      uv1 = tuv[0];
      uv2 = tuv[1];
      uv3 = tuv[2];
      uv4 = tuv[3];
      map_to_sphere(uv1, uv1 + 1, v1[0], v1[1], v1[2]);
      map_to_sphere(uv2, uv2 + 1, v2[0], v2[1], v2[2]);
      map_to_sphere(uv3, uv3 + 1, v3[0], v3[1], v3[2]);
      if (v4) {
        map_to_sphere(uv4, uv4 + 1, v4[0], v4[1], v4[2]);
      }
    }

    if (v4) {
      s1 = uv3[0] - uv1[0];
      s2 = uv4[0] - uv1[0];

      t1 = uv3[1] - uv1[1];
      t2 = uv4[1] - uv1[1];

      sub_v3_v3v3(e1, v3, v1);
      sub_v3_v3v3(e2, v4, v1);
    }
    else {
      s1 = uv2[0] - uv1[0];
      s2 = uv3[0] - uv1[0];

      t1 = uv2[1] - uv1[1];
      t2 = uv3[1] - uv1[1];

      sub_v3_v3v3(e1, v2, v1);
      sub_v3_v3v3(e2, v3, v1);
    }

    vtan[0] = (s1 * e2[0] - s2 * e1[0]);
    vtan[1] = (s1 * e2[1] - s2 * e1[1]);
    vtan[2] = (s1 * e2[2] - s2 * e1[2]);

    utan[0] = (t1 * e2[0] - t2 * e1[0]);
    utan[1] = (t1 * e2[1] - t2 * e1[1]);
    utan[2] = (t1 * e2[2] - t2 * e1[2]);
  }

  if (orco) {
    if (orcodata) {
      o1 = orcodata[mface->v1];
      o2 = orcodata[mface->v2];
      o3 = orcodata[mface->v3];

      if (mface->v4) {
        o4 = orcodata[mface->v4];

        interp_v3_v3v3v3v3(orco, o1, o2, o3, o4, w);
      }
      else {
        interp_v3_v3v3v3(orco, o1, o2, o3, w);
      }
      BKE_mesh_orco_verts_transform(mesh, reinterpret_cast<float (*)[3]>(orco), 1, true);
    }
    else {
      copy_v3_v3(orco, vec);
    }
  }
}
void psys_interpolate_uvs(const MTFace *tface, int quad, const float w[4], float r_uv[2])
{
  float v10 = tface->uv[0][0];
  float v11 = tface->uv[0][1];
  float v20 = tface->uv[1][0];
  float v21 = tface->uv[1][1];
  float v30 = tface->uv[2][0];
  float v31 = tface->uv[2][1];
  float v40, v41;

  if (quad) {
    v40 = tface->uv[3][0];
    v41 = tface->uv[3][1];

    r_uv[0] = w[0] * v10 + w[1] * v20 + w[2] * v30 + w[3] * v40;
    r_uv[1] = w[0] * v11 + w[1] * v21 + w[2] * v31 + w[3] * v41;
  }
  else {
    r_uv[0] = w[0] * v10 + w[1] * v20 + w[2] * v30;
    r_uv[1] = w[0] * v11 + w[1] * v21 + w[2] * v31;
  }
}

void psys_interpolate_mcol(const MCol *mcol, int quad, const float w[4], MCol *mc)
{
  const char *cp1, *cp2, *cp3, *cp4;
  char *cp;

  cp = reinterpret_cast<char *>(mc);
  cp1 = reinterpret_cast<const char *>(&mcol[0]);
  cp2 = reinterpret_cast<const char *>(&mcol[1]);
  cp3 = reinterpret_cast<const char *>(&mcol[2]);

  if (quad) {
    cp4 = reinterpret_cast<char *>(const_cast<MCol *>(&mcol[3]));

    cp[0] = int(w[0] * cp1[0] + w[1] * cp2[0] + w[2] * cp3[0] + w[3] * cp4[0]);
    cp[1] = int(w[0] * cp1[1] + w[1] * cp2[1] + w[2] * cp3[1] + w[3] * cp4[1]);
    cp[2] = int(w[0] * cp1[2] + w[1] * cp2[2] + w[2] * cp3[2] + w[3] * cp4[2]);
    cp[3] = int(w[0] * cp1[3] + w[1] * cp2[3] + w[2] * cp3[3] + w[3] * cp4[3]);
  }
  else {
    cp[0] = int(w[0] * cp1[0] + w[1] * cp2[0] + w[2] * cp3[0]);
    cp[1] = int(w[0] * cp1[1] + w[1] * cp2[1] + w[2] * cp3[1]);
    cp[2] = int(w[0] * cp1[2] + w[1] * cp2[2] + w[2] * cp3[2]);
    cp[3] = int(w[0] * cp1[3] + w[1] * cp2[3] + w[2] * cp3[3]);
  }
}

static float psys_interpolate_value_from_verts(
    Mesh *mesh, short from, int index, const float fw[4], const float *values)
{
  if (values == nullptr || index == -1) {
    return 0.0;
  }

  switch (from) {
    case PART_FROM_VERT:
      return values[index];
    case PART_FROM_FACE:
    case PART_FROM_VOLUME: {
      MFace *mfaces = static_cast<MFace *>(
          CustomData_get_layer_for_write(&mesh->fdata_legacy, CD_MFACE, mesh->totface_legacy));
      MFace *mf = &mfaces[index];
      return interpolate_particle_value(
          values[mf->v1], values[mf->v2], values[mf->v3], values[mf->v4], fw, mf->v4);
    }
  }
  return 0.0f;
}

/* conversion of pa->fw to origspace layer coordinates */
static void psys_w_to_origspace(const float w[4], float uv[2])
{
  uv[0] = w[1] + w[2];
  uv[1] = w[2] + w[3];
}

/* conversion of pa->fw to weights in face from origspace */
static void psys_origspace_to_w(OrigSpaceFace *osface, int quad, const float w[4], float neww[4])
{
  float v[4][3], co[3];

  v[0][0] = osface->uv[0][0];
  v[0][1] = osface->uv[0][1];
  v[0][2] = 0.0f;
  v[1][0] = osface->uv[1][0];
  v[1][1] = osface->uv[1][1];
  v[1][2] = 0.0f;
  v[2][0] = osface->uv[2][0];
  v[2][1] = osface->uv[2][1];
  v[2][2] = 0.0f;

  psys_w_to_origspace(w, co);
  co[2] = 0.0f;

  if (quad) {
    v[3][0] = osface->uv[3][0];
    v[3][1] = osface->uv[3][1];
    v[3][2] = 0.0f;
    interp_weights_poly_v3(neww, v, 4, co);
  }
  else {
    interp_weights_poly_v3(neww, v, 3, co);
    neww[3] = 0.0f;
  }
}

int psys_particle_dm_face_lookup(Mesh *mesh_final,
                                 Mesh *mesh_original,
                                 int findex_orig,
                                 const float fw[4],
                                 LinkNode **poly_nodes)
{
  MFace *mtessface_final;
  const OrigSpaceFace *osface_final;
  int pindex_orig;
  float uv[2];
  const float (*faceuv)[2];

  const int *index_mf_to_mpoly_deformed = nullptr;
  const int *index_mf_to_mpoly = nullptr;
  const int *index_mp_to_orig = nullptr;

  const int totface_final = mesh_final->totface_legacy;
  const int totface_deformed = mesh_original ? mesh_original->totface_legacy : totface_final;

  if (ELEM(0, totface_final, totface_deformed)) {
    return DMCACHE_NOTFOUND;
  }

  index_mf_to_mpoly = static_cast<const int *>(
      CustomData_get_layer(&mesh_final->fdata_legacy, CD_ORIGINDEX));
  index_mp_to_orig = static_cast<const int *>(
      CustomData_get_layer(&mesh_final->face_data, CD_ORIGINDEX));
  BLI_assert(index_mf_to_mpoly);

  if (mesh_original) {
    index_mf_to_mpoly_deformed = static_cast<const int *>(
        CustomData_get_layer(&mesh_original->fdata_legacy, CD_ORIGINDEX));
  }
  else {
    BLI_assert(mesh_final->runtime->deformed_only);
    index_mf_to_mpoly_deformed = index_mf_to_mpoly;
  }
  BLI_assert(index_mf_to_mpoly_deformed);

  pindex_orig = index_mf_to_mpoly_deformed[findex_orig];

  if (mesh_original == nullptr) {
    mesh_original = mesh_final;
  }

  index_mf_to_mpoly_deformed = nullptr;

  mtessface_final = static_cast<MFace *>(CustomData_get_layer_for_write(
      &mesh_final->fdata_legacy, CD_MFACE, mesh_final->totface_legacy));
  osface_final = static_cast<OrigSpaceFace *>(CustomData_get_layer_for_write(
      &mesh_final->fdata_legacy, CD_ORIGSPACE, mesh_final->totface_legacy));

  if (osface_final == nullptr) {
    /* Assume we don't need osface_final data, and we get a direct 1-1 mapping... */
    if (findex_orig < totface_final) {
      // printf("\tNO CD_ORIGSPACE, assuming not needed\n");
      return findex_orig;
    }

    printf("\tNO CD_ORIGSPACE, error out of range\n");
    return DMCACHE_NOTFOUND;
  }
  if (findex_orig >= mesh_original->totface_legacy) {
    return DMCACHE_NOTFOUND; /* index not in the original mesh */
  }

  psys_w_to_origspace(fw, uv);

  if (poly_nodes) {
    /* we can have a restricted linked list of faces to check, faster! */
    LinkNode *tessface_node = poly_nodes[pindex_orig];

    for (; tessface_node; tessface_node = tessface_node->next) {
      int findex_dst = POINTER_AS_INT(tessface_node->link);
      faceuv = osface_final[findex_dst].uv;

      /* check that this intersects - Its possible this misses :/ -
       * could also check its not between */
      if (mtessface_final[findex_dst].v4) {
        if (isect_point_quad_v2(uv, faceuv[0], faceuv[1], faceuv[2], faceuv[3])) {
          return findex_dst;
        }
      }
      else if (isect_point_tri_v2(uv, faceuv[0], faceuv[1], faceuv[2])) {
        return findex_dst;
      }
    }
  }
  else { /* if we have no node, try every face */
    for (int findex_dst = 0; findex_dst < totface_final; findex_dst++) {
      /* If current tessface from 'final' DM and orig tessface (given by index)
       * map to the same orig poly. */
      if (BKE_mesh_origindex_mface_mpoly(index_mf_to_mpoly, index_mp_to_orig, findex_dst) ==
          pindex_orig)
      {
        faceuv = osface_final[findex_dst].uv;

        /* check that this intersects - Its possible this misses :/ -
         * could also check its not between */
        if (mtessface_final[findex_dst].v4) {
          if (isect_point_quad_v2(uv, faceuv[0], faceuv[1], faceuv[2], faceuv[3])) {
            return findex_dst;
          }
        }
        else if (isect_point_tri_v2(uv, faceuv[0], faceuv[1], faceuv[2])) {
          return findex_dst;
        }
      }
    }
  }

  return DMCACHE_NOTFOUND;
}

static int psys_map_index_on_dm(Mesh *mesh,
                                int from,
                                int index,
                                int index_dmcache,
                                const float fw[4],
                                float /*foffset*/,
                                int *mapindex,
                                float mapfw[4])
{
  if (index < 0) {
    return 0;
  }

  if (mesh->runtime->deformed_only || index_dmcache == DMCACHE_ISCHILD) {
    /* for meshes that are either only deformed or for child particles, the
     * index and fw do not require any mapping, so we can directly use it */
    if (from == PART_FROM_VERT) {
      if (index >= mesh->verts_num) {
        return 0;
      }

      *mapindex = index;
    }
    else { /* FROM_FACE/FROM_VOLUME */
      if (index >= mesh->totface_legacy) {
        return 0;
      }

      *mapindex = index;
      copy_v4_v4(mapfw, fw);
    }
  }
  else {
    /* for other meshes that have been modified, we try to map the particle
     * to their new location, which means a different index, and for faces
     * also a new face interpolation weights */
    if (from == PART_FROM_VERT) {
      if (index_dmcache == DMCACHE_NOTFOUND || index_dmcache >= mesh->verts_num) {
        return 0;
      }

      *mapindex = index_dmcache;
    }
    else { /* FROM_FACE/FROM_VOLUME */
           /* find a face on the derived mesh that uses this face */
      int i = index_dmcache;

      if (i == DMCACHE_NOTFOUND || i >= mesh->totface_legacy) {
        return 0;
      }

      *mapindex = i;

      /* modify the original weights to become
       * weights for the derived mesh face */
      OrigSpaceFace *osface = static_cast<OrigSpaceFace *>(
          CustomData_get_layer_for_write(&mesh->fdata_legacy, CD_ORIGSPACE, mesh->totface_legacy));
      const MFace *mfaces = static_cast<const MFace *>(
          CustomData_get_layer(&mesh->fdata_legacy, CD_MFACE));
      const MFace *mface = &mfaces[i];

      if (osface == nullptr) {
        mapfw[0] = mapfw[1] = mapfw[2] = mapfw[3] = 0.0f;
      }
      else {
        psys_origspace_to_w(&osface[i], mface->v4, fw, mapfw);
      }
    }
  }

  return 1;
}

void psys_particle_on_dm(Mesh *mesh_final,
                         int from,
                         int index,
                         int index_dmcache,
                         const float fw[4],
                         float foffset,
                         float vec[3],
                         float nor[3],
                         float utan[3],
                         float vtan[3],
                         float orco[3])
{
  float tmpnor[3], mapfw[4];
  const float (*orcodata)[3];
  int mapindex;

  if (!psys_map_index_on_dm(mesh_final, from, index, index_dmcache, fw, foffset, &mapindex, mapfw))
  {
    if (vec) {
      vec[0] = vec[1] = vec[2] = 0.0;
    }
    if (nor) {
      nor[0] = nor[1] = 0.0;
      nor[2] = 1.0;
    }
    if (orco) {
      orco[0] = orco[1] = orco[2] = 0.0;
    }
    if (utan) {
      utan[0] = utan[1] = utan[2] = 0.0;
    }
    if (vtan) {
      vtan[0] = vtan[1] = vtan[2] = 0.0;
    }

    return;
  }

  orcodata = static_cast<const float (*)[3]>(
      CustomData_get_layer(&mesh_final->vert_data, CD_ORCO));
  const Span<float3> vert_normals = mesh_final->vert_normals();

  if (from == PART_FROM_VERT) {
    const Span<float3> vert_positions = mesh_final->vert_positions();
    copy_v3_v3(vec, vert_positions[mapindex]);

    if (nor) {
      copy_v3_v3(nor, vert_normals[mapindex]);
    }

    if (orco) {
      if (orcodata) {
        copy_v3_v3(orco, orcodata[mapindex]);
        BKE_mesh_orco_verts_transform(mesh_final, reinterpret_cast<float (*)[3]>(orco), 1, true);
      }
      else {
        copy_v3_v3(orco, vec);
      }
    }

    if (utan && vtan) {
      utan[0] = utan[1] = utan[2] = 0.0f;
      vtan[0] = vtan[1] = vtan[2] = 0.0f;
    }
  }
  else { /* PART_FROM_FACE / PART_FROM_VOLUME */
    MFace *mface;
    MTFace *mtface;

    MFace *mfaces = static_cast<MFace *>(CustomData_get_layer_for_write(
        &mesh_final->fdata_legacy, CD_MFACE, mesh_final->totface_legacy));
    mface = &mfaces[mapindex];
    const Span<float3> vert_positions = mesh_final->vert_positions();
    mtface = static_cast<MTFace *>(CustomData_get_layer_for_write(
        &mesh_final->fdata_legacy, CD_MTFACE, mesh_final->totface_legacy));

    if (mtface) {
      mtface += mapindex;
    }

    if (from == PART_FROM_VOLUME) {
      psys_interpolate_face(mesh_final,
                            reinterpret_cast<const float (*)[3]>(vert_positions.data()),
                            reinterpret_cast<const float (*)[3]>(vert_normals.data()),
                            mface,
                            mtface,
                            orcodata,
                            mapfw,
                            vec,
                            tmpnor,
                            utan,
                            vtan,
                            orco);
      if (nor) {
        copy_v3_v3(nor, tmpnor);
      }

      /* XXX Why not normalize tmpnor before copying it into nor??? -- mont29 */
      normalize_v3(tmpnor);

      mul_v3_fl(tmpnor, -foffset);
      add_v3_v3(vec, tmpnor);
    }
    else {
      psys_interpolate_face(mesh_final,
                            reinterpret_cast<const float (*)[3]>(vert_positions.data()),
                            reinterpret_cast<const float (*)[3]>(vert_normals.data()),
                            mface,
                            mtface,
                            orcodata,
                            mapfw,
                            vec,
                            nor,
                            utan,
                            vtan,
                            orco);
    }
  }
}

float psys_particle_value_from_verts(Mesh *mesh, short from, ParticleData *pa, float *values)
{
  float mapfw[4];
  int mapindex;

  if (!psys_map_index_on_dm(
          mesh, from, pa->num, pa->num_dmcache, pa->fuv, pa->foffset, &mapindex, mapfw))
  {
    return 0.0f;
  }

  return psys_interpolate_value_from_verts(mesh, from, mapindex, mapfw, values);
}

ParticleSystemModifierData *psys_get_modifier(Object *ob, ParticleSystem *psys)
{
  ParticleSystemModifierData *psmd;

  for (ModifierData &md : ob->modifiers) {
    if (md.type == eModifierType_ParticleSystem) {
      psmd = reinterpret_cast<ParticleSystemModifierData *>(&md);
      if (psmd->psys == psys) {
        return psmd;
      }
    }
  }
  return nullptr;
}

/** \} */

/* -------------------------------------------------------------------- */
/** \name Particles on a Shape
 * \{ */

/* ready for future use */
static void psys_particle_on_shape(int /*distr*/,
                                   int /*index*/,
                                   float * /*fuv*/,
                                   float vec[3],
                                   float nor[3],
                                   float utan[3],
                                   float vtan[3],
                                   float orco[3])
{
  /* TODO */
  const float zerovec[3] = {0.0f, 0.0f, 0.0f};
  if (vec) {
    copy_v3_v3(vec, zerovec);
  }
  if (nor) {
    copy_v3_v3(nor, zerovec);
  }
  if (utan) {
    copy_v3_v3(utan, zerovec);
  }
  if (vtan) {
    copy_v3_v3(vtan, zerovec);
  }
  if (orco) {
    copy_v3_v3(orco, zerovec);
  }
}

/** \} */

/* -------------------------------------------------------------------- */
/** \name Particles on Emitter
 * \{ */

void psys_emitter_customdata_mask(ParticleSystem *psys, CustomData_MeshMasks *r_cddata_masks)
{
  MTex *mtex;
  int i;

  if (!psys->part) {
    return;
  }

  for (i = 0; i < MAX_MTEX; i++) {
    mtex = psys->part->mtex[i];
    if (mtex && mtex->mapto && (mtex->texco & TEXCO_UV)) {
      r_cddata_masks->fmask |= CD_MASK_MTFACE;
    }
  }

  if (psys->part->tanfac != 0.0f) {
    r_cddata_masks->fmask |= CD_MASK_MTFACE;
  }

  /* Ask for vertex-groups if we need them. */
  for (i = 0; i < PSYS_TOT_VG; i++) {
    if (psys->vgroup[i]) {
      r_cddata_masks->vmask |= CD_MASK_MDEFORMVERT;
      break;
    }
  }

  /* particles only need this if they are after a non deform modifier, and
   * the modifier stack will only create them in that case. */
  r_cddata_masks->lmask |= CD_MASK_ORIGSPACE_MLOOP;
  /* XXX Check we do need all those? */
  r_cddata_masks->vmask |= CD_MASK_ORIGINDEX;
  r_cddata_masks->emask |= CD_MASK_ORIGINDEX;
  r_cddata_masks->pmask |= CD_MASK_ORIGINDEX;

  r_cddata_masks->vmask |= CD_MASK_ORCO;
}

void psys_particle_on_emitter(ParticleSystemModifierData *psmd,
                              int from,
                              int index,
                              int index_dmcache,
                              float fuv[4],
                              float foffset,
                              float vec[3],
                              float nor[3],
                              float utan[3],
                              float vtan[3],
                              float orco[3])
{
  if (psmd && psmd->mesh_final) {
    if (psmd->psys->part->distr == PART_DISTR_GRID && psmd->psys->part->from != PART_FROM_VERT) {
      if (vec) {
        copy_v3_v3(vec, fuv);
      }

      if (orco) {
        copy_v3_v3(orco, fuv);
      }
      return;
    }
    /* we can't use the num_dmcache */
    psys_particle_on_dm(
        psmd->mesh_final, from, index, index_dmcache, fuv, foffset, vec, nor, utan, vtan, orco);
  }
  else {
    psys_particle_on_shape(from, index, fuv, vec, nor, utan, vtan, orco);
  }
}

/** \} */

/* -------------------------------------------------------------------- */
/** \name Path Cache
 * \{ */

void precalc_guides(ParticleSimulationData *sim, ListBaseT<EffectorCache> *effectors)
{
  EffectedPoint point;
  ParticleKey state;
  EffectorData efd;
  ParticleSystem *psys = sim->psys;
  EffectorWeights *weights = sim->psys->part->effector_weights;
  GuideEffectorData *data;
  PARTICLE_P;

  if (!effectors) {
    return;
  }

  LOOP_PARTICLES
  {
    psys_particle_on_emitter(sim->psmd,
                             sim->psys->part->from,
                             pa->num,
                             pa->num_dmcache,
                             pa->fuv,
                             pa->foffset,
                             state.co,
                             nullptr,
                             nullptr,
                             nullptr,
                             nullptr);

    mul_m4_v3(sim->ob->object_to_world().ptr(), state.co);
    mul_mat3_m4_v3(sim->ob->object_to_world().ptr(), state.vel);

    pd_point_from_particle(sim, pa, &state, &point);

    for (EffectorCache &eff : *effectors) {
      if (eff.pd->forcefield != PFIELD_GUIDE) {
        continue;
      }

      if (!eff.guide_data) {
        eff.guide_data = MEM_new_array_zeroed<GuideEffectorData>(psys->totpart,
                                                                 "GuideEffectorData");
      }

      data = eff.guide_data + p;

      sub_v3_v3v3(efd.vec_to_point, state.co, eff.guide_loc);
      copy_v3_v3(efd.nor, eff.guide_dir);
      efd.distance = len_v3(efd.vec_to_point);

      copy_v3_v3(data->vec_to_point, efd.vec_to_point);
      data->strength = effector_falloff(&eff, &efd, &point, weights);
    }
  }
}

bool do_guides(Depsgraph *depsgraph,
               ParticleSettings *part,
               ListBaseT<EffectorCache> *effectors,
               ParticleKey *state,
               int index,
               float time)
{
  CurveMapping *clumpcurve = (part->child_flag & PART_CHILD_USE_CLUMP_CURVE) ? part->clumpcurve :
                                                                               nullptr;
  CurveMapping *roughcurve = (part->child_flag & PART_CHILD_USE_ROUGH_CURVE) ? part->roughcurve :
                                                                               nullptr;
  PartDeflect *pd;
  Curve *cu;
  GuideEffectorData *data;

  float effect[3] = {0.0f, 0.0f, 0.0f}, veffect[3] = {0.0f, 0.0f, 0.0f};
  float guidevec[4], guidedir[3], rot2[4], temp[3];
  float guidetime, radius, weight, angle, totstrength = 0.0f;
  float vec_to_point[3];

  if (effectors) {
    for (EffectorCache &eff : *effectors) {
      pd = eff.pd;

      if (pd->forcefield != PFIELD_GUIDE) {
        continue;
      }

      data = eff.guide_data + index;

      if (data->strength <= 0.0f) {
        continue;
      }

      guidetime = time / (1.0f - pd->free_end);

      if (guidetime > 1.0f) {
        continue;
      }

      cu = id_cast<Curve *>(eff.ob->data);

      if (pd->flag & PFIELD_GUIDE_PATH_ADD) {
        if (BKE_where_on_path(eff.ob,
                              data->strength * guidetime,
                              guidevec,
                              guidedir,
                              nullptr,
                              &radius,
                              &weight) == 0)
        {
          return false;
        }
      }
      else {
        if (BKE_where_on_path(eff.ob, guidetime, guidevec, guidedir, nullptr, &radius, &weight) ==
            0)
        {
          return false;
        }
      }

      mul_m4_v3(eff.ob->object_to_world().ptr(), guidevec);
      mul_mat3_m4_v3(eff.ob->object_to_world().ptr(), guidedir);

      normalize_v3(guidedir);

      copy_v3_v3(vec_to_point, data->vec_to_point);

      if (guidetime != 0.0f) {
        /* curve direction */
        cross_v3_v3v3(temp, eff.guide_dir, guidedir);
        angle = dot_v3v3(eff.guide_dir, guidedir) / len_v3(eff.guide_dir);
        angle = safe_acosf(angle);
        axis_angle_to_quat(rot2, temp, angle);
        mul_qt_v3(rot2, vec_to_point);

        /* curve tilt */
        axis_angle_to_quat(rot2, guidedir, guidevec[3] - eff.guide_loc[3]);
        mul_qt_v3(rot2, vec_to_point);
      }

      /* curve taper */
      if (cu->taperobj) {
        mul_v3_fl(vec_to_point,
                  BKE_displist_calc_taper(depsgraph,
                                          eff.scene,
                                          cu->taperobj,
                                          int(data->strength * guidetime * 100.0f),
                                          100));
      }
      else { /* Curve size. */
        if (cu->flag & CU_PATH_RADIUS) {
          mul_v3_fl(vec_to_point, radius);
        }
      }

      if (clumpcurve) {
        BKE_curvemapping_changed_all(clumpcurve);
      }
      if (roughcurve) {
        BKE_curvemapping_changed_all(roughcurve);
      }

      {
        ParticleKey key;
        const float par_co[3] = {0.0f, 0.0f, 0.0f};
        const float par_vel[3] = {0.0f, 0.0f, 0.0f};
        const float par_rot[4] = {1.0f, 0.0f, 0.0f, 0.0f};
        const float orco_offset[3] = {0.0f, 0.0f, 0.0f};

        copy_v3_v3(key.co, vec_to_point);
        do_kink(&key,
                par_co,
                par_vel,
                par_rot,
                guidetime,
                pd->kink_freq,
                pd->kink_shape,
                pd->kink_amp,
                0.0f,
                pd->kink,
                pd->kink_axis,
                nullptr,
                0);
        do_clump(&key,
                 par_co,
                 guidetime,
                 orco_offset,
                 pd->clump_fac,
                 pd->clump_pow,
                 1.0f,
                 part->child_flag & PART_CHILD_USE_CLUMP_NOISE,
                 part->clump_noise_size,
                 clumpcurve);
        copy_v3_v3(vec_to_point, key.co);
      }

      add_v3_v3(vec_to_point, guidevec);

      // sub_v3_v3v3(pa_loc, pa_loc, pa_zero);
      madd_v3_v3fl(effect, vec_to_point, data->strength);
      madd_v3_v3fl(veffect, guidedir, data->strength);
      totstrength += data->strength;

      if (pd->flag & PFIELD_GUIDE_PATH_WEIGHT) {
        totstrength *= weight;
      }
    }
  }

  if (totstrength != 0.0f) {
    if (totstrength > 1.0f) {
      mul_v3_fl(effect, 1.0f / totstrength);
    }
    CLAMP(totstrength, 0.0f, 1.0f);
    // add_v3_v3(effect, pa_zero);
    interp_v3_v3v3(state->co, state->co, effect, totstrength);

    normalize_v3(veffect);
    mul_v3_fl(veffect, len_v3(state->vel));
    copy_v3_v3(state->vel, veffect);
    return true;
  }
  return false;
}

static void do_path_effectors(ParticleSimulationData *sim,
                              int i,
                              ParticleCacheKey *ca,
                              int k,
                              int steps,
                              float * /*rootco*/,
                              float effector,
                              float /*dfra*/,
                              float /*cfra*/,
                              float *length,
                              float *vec)
{
  float force[3] = {0.0f, 0.0f, 0.0f};
  ParticleKey eff_key;
  EffectedPoint epoint;

  /* Don't apply effectors for dynamic hair, otherwise the effectors don't get applied twice. */
  if (sim->psys->flag & PSYS_HAIR_DYNAMICS) {
    return;
  }

  copy_v3_v3(eff_key.co, (ca - 1)->co);
  copy_v3_v3(eff_key.vel, (ca - 1)->vel);
  copy_qt_qt(eff_key.rot, (ca - 1)->rot);

  pd_point_from_particle(sim, sim->psys->particles + i, &eff_key, &epoint);
  BKE_effectors_apply(sim->psys->effectors,
                      sim->colliders,
                      sim->psys->part->effector_weights,
                      &epoint,
                      force,
                      nullptr,
                      nullptr);

  mul_v3_fl(force,
            effector * powf(float(k) / float(steps), 100.0f * sim->psys->part->eff_hair) /
                float(steps));

  add_v3_v3(force, vec);

  normalize_v3(force);

  if (k < steps) {
    sub_v3_v3v3(vec, (ca + 1)->co, ca->co);
  }

  madd_v3_v3v3fl(ca->co, (ca - 1)->co, force, *length);

  if (k < steps) {
    *length = len_v3(vec);
  }
}
static void offset_child(ChildParticle *cpa,
                         ParticleKey *par,
                         float *par_rot,
                         ParticleKey *child,
                         float flat,
                         float radius)
{
  copy_v3_v3(child->co, cpa->fuv);
  mul_v3_fl(child->co, radius);

  child->co[0] *= flat;

  copy_v3_v3(child->vel, par->vel);

  if (par_rot) {
    mul_qt_v3(par_rot, child->co);
    copy_qt_qt(child->rot, par_rot);
  }
  else {
    unit_qt(child->rot);
  }

  add_v3_v3(child->co, par->co);
}
float *psys_cache_vgroup(Mesh *mesh, ParticleSystem *psys, int vgroup)
{
  float *vg = nullptr;

  if (vgroup < 0) {
    /* hair dynamics pinning vgroup */
  }
  else if (psys->vgroup[vgroup]) {
    const MDeformVert *dvert = mesh->deform_verts().data();
    if (dvert) {
      int totvert = mesh->verts_num, i;
      vg = MEM_new_array_zeroed<float>(totvert, "vg_cache");
      if (psys->vg_neg & (1 << vgroup)) {
        for (i = 0; i < totvert; i++) {
          vg[i] = 1.0f - BKE_defvert_find_weight(&dvert[i], psys->vgroup[vgroup] - 1);
        }
      }
      else {
        for (i = 0; i < totvert; i++) {
          vg[i] = BKE_defvert_find_weight(&dvert[i], psys->vgroup[vgroup] - 1);
        }
      }
    }
  }
  return vg;
}
void psys_find_parents(ParticleSimulationData *sim, const bool use_render_params)
{
  ParticleSystem *psys = sim->psys;
  ParticleSettings *part = sim->psys->part;
  KDTree<float3> *tree;
  ChildParticle *cpa;
  ParticleTexture ptex;
  int p, totparent, totchild = sim->psys->totchild;
  float co[3], orco[3];
  int from = PART_FROM_FACE;
  totparent = int(totchild * part->parents * 0.3f);

  if (use_render_params && part->child_percent && part->child_render_percent) {
    totparent *= float(part->child_percent) / float(part->child_render_percent);
  }

  /* hard limit, workaround for it being ignored above */
  totparent = std::min(sim->psys->totpart, totparent);

  tree = kdtree_new<float3>(totparent);

  for (p = 0, cpa = sim->psys->child; p < totparent; p++, cpa++) {
    psys_particle_on_emitter(sim->psmd,
                             from,
                             cpa->num,
                             DMCACHE_ISCHILD,
                             cpa->fuv,
                             cpa->foffset,
                             co,
                             nullptr,
                             nullptr,
                             nullptr,
                             orco);

    /* Check if particle doesn't exist because of texture influence.
     * Insert only existing particles into kdtree. */
    get_cpa_texture(sim->psmd->mesh_final,
                    psys,
                    part,
                    psys->particles + cpa->pa[0],
                    p,
                    cpa->num,
                    cpa->fuv,
                    orco,
                    &ptex,
                    PAMAP_DENS | PAMAP_CHILD,
                    psys->cfra);

    if (ptex.exist >= psys_frand(psys, p + 24)) {
      kdtree_insert<float3>(tree, p, orco);
    }
  }

  kdtree_balance<float3>(tree);

  for (; p < totchild; p++, cpa++) {
    psys_particle_on_emitter(sim->psmd,
                             from,
                             cpa->num,
                             DMCACHE_ISCHILD,
                             cpa->fuv,
                             cpa->foffset,
                             co,
                             nullptr,
                             nullptr,
                             nullptr,
                             orco);
    cpa->parent = kdtree_find_nearest<float3>(tree, orco, nullptr);
  }

  kdtree_free<float3>(tree);
}

static bool psys_thread_context_init_path(ParticleThreadContext *ctx,
                                          ParticleSimulationData *sim,
                                          Scene *scene,
                                          float cfra,
                                          const bool editupdate,
                                          const bool use_render_params)
{
  ParticleSystem *psys = sim->psys;
  ParticleSettings *part = psys->part;
  int totparent = 0, between = 0;
  int segments = 1 << part->draw_step;
  int totchild = psys->totchild;

  psys_thread_context_init(ctx, sim);

  /*---start figuring out what is actually wanted---*/
  if (psys_in_edit_mode(sim->depsgraph, psys)) {
    ParticleEditSettings *pset = &scene->toolsettings->particle;

    if ((use_render_params == 0) &&
        (psys_orig_edit_get(psys) == nullptr || pset->flag & PE_DRAW_PART) == 0)
    {
      totchild = 0;
    }

    segments = 1 << pset->draw_step;
  }

  if (totchild && part->childtype == PART_CHILD_FACES) {
    totparent = int(totchild * part->parents * 0.3f);

    if (use_render_params && part->child_percent && part->child_render_percent) {
      totparent *= float(part->child_percent) / float(part->child_render_percent);
    }

    /* part->parents could still be 0 so we can't test with totparent */
    between = 1;
  }

  if (use_render_params) {
    segments = 1 << part->ren_step;
  }
  else {
    totchild = int(float(totchild) * float(part->disp) / 100.0f);
  }

  totparent = std::min(totparent, totchild);

  if (totchild == 0) {
    return false;
  }

  /* fill context values */
  ctx->between = between;
  ctx->segments = segments;
  if (ELEM(part->kink, PART_KINK_SPIRAL)) {
    ctx->extra_segments = max_ii(part->kink_extra_steps, 1);
  }
  else {
    ctx->extra_segments = 0;
  }
  ctx->totchild = totchild;
  ctx->totparent = totparent;
  ctx->parent_pass = 0;
  ctx->cfra = cfra;
  ctx->editupdate = editupdate;

  psys_sim_data_init(&ctx->sim);

  /* cache all relevant vertex groups if they exist */
  ctx->vg_length = psys_cache_vgroup(ctx->mesh, psys, PSYS_VG_LENGTH);
  ctx->vg_clump = psys_cache_vgroup(ctx->mesh, psys, PSYS_VG_CLUMP);
  ctx->vg_kink = psys_cache_vgroup(ctx->mesh, psys, PSYS_VG_KINK);
  ctx->vg_rough1 = psys_cache_vgroup(ctx->mesh, psys, PSYS_VG_ROUGH1);
  ctx->vg_rough2 = psys_cache_vgroup(ctx->mesh, psys, PSYS_VG_ROUGH2);
  ctx->vg_roughe = psys_cache_vgroup(ctx->mesh, psys, PSYS_VG_ROUGHE);
  ctx->vg_twist = psys_cache_vgroup(ctx->mesh, psys, PSYS_VG_TWIST);
  if (psys->part->flag & PART_CHILD_EFFECT) {
    ctx->vg_effector = psys_cache_vgroup(ctx->mesh, psys, PSYS_VG_EFFECTOR);
  }

  /* prepare curvemapping tables */
  if ((part->child_flag & PART_CHILD_USE_CLUMP_CURVE) && part->clumpcurve) {
    ctx->clumpcurve = BKE_curvemapping_copy(part->clumpcurve);
    BKE_curvemapping_changed_all(ctx->clumpcurve);
  }
  else {
    ctx->clumpcurve = nullptr;
  }
  if ((part->child_flag & PART_CHILD_USE_ROUGH_CURVE) && part->roughcurve) {
    ctx->roughcurve = BKE_curvemapping_copy(part->roughcurve);
    BKE_curvemapping_changed_all(ctx->roughcurve);
  }
  else {
    ctx->roughcurve = nullptr;
  }
  if ((part->child_flag & PART_CHILD_USE_TWIST_CURVE) && part->twistcurve) {
    ctx->twistcurve = BKE_curvemapping_copy(part->twistcurve);
    BKE_curvemapping_changed_all(ctx->twistcurve);
  }
  else {
    ctx->twistcurve = nullptr;
  }

  return true;
}

static void psys_task_init_path(ParticleTask *task, ParticleSimulationData *sim)
{
  /* init random number generator */
  int seed = 31415926 + sim->psys->seed;

  task->rng_path = BLI_rng_new(seed);
}

/* NOTE: this function must be thread safe, except for branching! */
static void psys_thread_create_path(ParticleTask *task,
                                    ChildParticle *cpa,
                                    ParticleCacheKey *child_keys,
                                    int i)
{
  ParticleThreadContext *ctx = task->ctx;
  Object *ob = ctx->sim.ob;
  ParticleSystem *psys = ctx->sim.psys;
  ParticleSettings *part = psys->part;
  ParticleCacheKey **cache = psys->childcache;
  PTCacheEdit *edit = psys_orig_edit_get(psys);
  ParticleCacheKey **pcache = psys_in_edit_mode(ctx->sim.depsgraph, psys) && edit ?
                                  edit->pathcache :
                                  psys->pathcache;
  ParticleCacheKey *child, *key[4];
  ParticleTexture ptex;
  float *cpa_fuv = nullptr, *par_rot = nullptr, rot[4];
  float orco[3], hairmat[4][4], dvec[3], off1[4][3], off2[4][3];
  float eff_length, eff_vec[3], weight[4];
  int k, cpa_num;
  short cpa_from;

  if (!pcache) {
    return;
  }

  if (ctx->between) {
    ParticleData *pa = psys->particles + cpa->pa[0];
    int w, needupdate;
    float foffset, wsum = 0.0f;
    float co[3];
    float p_min = part->parting_min;
    float p_max = part->parting_max;
    /* Virtual parents don't work nicely with parting. */
    float p_fac = part->parents > 0.0f ? 0.0f : part->parting_fac;

    if (ctx->editupdate) {
      needupdate = 0;
      w = 0;
      while (w < 4 && cpa->pa[w] >= 0) {
        if (edit->points[cpa->pa[w]].flag & PEP_EDIT_RECALC) {
          needupdate = 1;
          break;
        }
        w++;
      }

      if (!needupdate) {
        return;
      }

      memset(child_keys, 0, sizeof(*child_keys) * (ctx->segments + 1));
    }

    /* get parent paths */
    for (w = 0; w < 4; w++) {
      if (cpa->pa[w] >= 0) {
        key[w] = pcache[cpa->pa[w]];
        weight[w] = cpa->w[w];
      }
      else {
        key[w] = pcache[0];
        weight[w] = 0.0f;
      }
    }

    /* modify weights to create parting */
    if (p_fac > 0.0f) {
      const ParticleCacheKey *key_0_last = pcache_key_segment_endpoint_safe(key[0]);
      for (w = 0; w < 4; w++) {
        if (w && (weight[w] > 0.0f)) {
          const ParticleCacheKey *key_w_last = pcache_key_segment_endpoint_safe(key[w]);
          float d;
          if (part->flag & PART_CHILD_LONG_HAIR) {
            /* For long hair use tip distance/root distance as parting
             * factor instead of root to tip angle. */
            float d1 = len_v3v3(key[0]->co, key[w]->co);
            float d2 = len_v3v3(key_0_last->co, key_w_last->co);

            d = d1 > 0.0f ? d2 / d1 - 1.0f : 10000.0f;
          }
          else {
            float v1[3], v2[3];
            sub_v3_v3v3(v1, key_0_last->co, key[0]->co);
            sub_v3_v3v3(v2, key_w_last->co, key[w]->co);
            normalize_v3(v1);
            normalize_v3(v2);

            d = RAD2DEGF(safe_acosf(dot_v3v3(v1, v2)));
          }

          if (p_max > p_min) {
            d = (d - p_min) / (p_max - p_min);
          }
          else {
            d = (d - p_min) <= 0.0f ? 0.0f : 1.0f;
          }

          CLAMP(d, 0.0f, 1.0f);

          if (d > 0.0f) {
            weight[w] *= (1.0f - d);
          }
        }
        wsum += weight[w];
      }
      for (w = 0; w < 4; w++) {
        weight[w] /= wsum;
      }

      interp_v4_v4v4(weight, cpa->w, weight, p_fac);
    }

    /* get the original coordinates (orco) for texture usage */
    cpa_num = cpa->num;

    foffset = cpa->foffset;
    cpa_fuv = cpa->fuv;
    cpa_from = PART_FROM_FACE;

    psys_particle_on_emitter(ctx->sim.psmd,
                             cpa_from,
                             cpa_num,
                             DMCACHE_ISCHILD,
                             cpa->fuv,
                             foffset,
                             co,
                             nullptr,
                             nullptr,
                             nullptr,
                             orco);

    mul_m4_v3(ob->object_to_world().ptr(), co);

    for (w = 0; w < 4; w++) {
      sub_v3_v3v3(off1[w], co, key[w]->co);
    }

    psys_mat_hair_to_global(ob, ctx->sim.psmd->mesh_final, psys->part->from, pa, hairmat);
  }
  else {
    ParticleData *pa = psys->particles + cpa->parent;
    float co[3];
    if (ctx->editupdate) {
      if (!(edit->points[cpa->parent].flag & PEP_EDIT_RECALC)) {
        return;
      }

      memset(child_keys, 0, sizeof(*child_keys) * (ctx->segments + 1));
    }

    /* get the parent path */
    key[0] = pcache[cpa->parent];

    /* get the original coordinates (orco) for texture usage */
    cpa_from = part->from;

    /*
     * NOTE: Should in theory be the same as:
     * cpa_num = psys_particle_dm_face_lookup(
     *        ctx->sim.psmd->dm_final,
     *        ctx->sim.psmd->dm_deformed,
     *        pa->num, pa->fuv,
     *        nullptr);
     */
    cpa_num = ELEM(pa->num_dmcache, DMCACHE_ISCHILD, DMCACHE_NOTFOUND) ? pa->num : pa->num_dmcache;

    /* XXX hack to avoid messed up particle num and subsequent crash (#40733) */
    if (cpa_num > ctx->sim.psmd->mesh_final->totface_legacy) {
      cpa_num = 0;
    }
    cpa_fuv = pa->fuv;

    psys_particle_on_emitter(ctx->sim.psmd,
                             cpa_from,
                             cpa_num,
                             DMCACHE_ISCHILD,
                             cpa_fuv,
                             pa->foffset,
                             co,
                             nullptr,
                             nullptr,
                             nullptr,
                             orco);

    psys_mat_hair_to_global(ob, ctx->sim.psmd->mesh_final, psys->part->from, pa, hairmat);
  }

  child_keys->segments = ctx->segments;

  /* get different child parameters from textures & vgroups */
  get_child_modifier_parameters(part, ctx, cpa, cpa_from, cpa_num, cpa_fuv, orco, &ptex);

  if (ptex.exist < psys_frand(psys, i + 24)) {
    child_keys->segments = -1;
    return;
  }

  /* create the child path */
  for (k = 0, child = child_keys; k <= ctx->segments; k++, child++) {
    if (ctx->between) {
      int w = 0;

      zero_v3(child->co);
      zero_v3(child->vel);
      unit_qt(child->rot);

      for (w = 0; w < 4; w++) {
        copy_v3_v3(off2[w], off1[w]);

        if (part->flag & PART_CHILD_LONG_HAIR) {
          /* Use parent rotation (in addition to emission location) to determine child offset. */
          if (k) {
            mul_qt_v3((key[w] + k)->rot, off2[w]);
          }

          /* Fade the effect of rotation for even lengths in the end */
          project_v3_v3v3(dvec, off2[w], (key[w] + k)->vel);
          madd_v3_v3fl(off2[w], dvec, -float(k) / float(ctx->segments));
        }

        add_v3_v3(off2[w], (key[w] + k)->co);
      }

      /* child position is the weighted sum of parent positions */
      interp_v3_v3v3v3v3(child->co, off2[0], off2[1], off2[2], off2[3], weight);
      interp_v3_v3v3v3v3(child->vel,
                         (key[0] + k)->vel,
                         (key[1] + k)->vel,
                         (key[2] + k)->vel,
                         (key[3] + k)->vel,
                         weight);

      copy_qt_qt(child->rot, (key[0] + k)->rot);
    }
    else {
      if (k) {
        mul_qt_qtqt(rot, (key[0] + k)->rot, key[0]->rot);
        par_rot = rot;
      }
      else {
        par_rot = key[0]->rot;
      }
      /* offset the child from the parent position */
      offset_child(cpa,
                   reinterpret_cast<ParticleKey *>(key[0] + k),
                   par_rot,
                   reinterpret_cast<ParticleKey *>(child),
                   part->childflat,
                   part->childrad);
    }

    child->time = float(k) / float(ctx->segments);
  }

  /* apply effectors */
  if (part->flag & PART_CHILD_EFFECT) {
    for (k = 0, child = child_keys; k <= ctx->segments; k++, child++) {
      if (k) {
        do_path_effectors(&ctx->sim,
                          cpa->pa[0],
                          child,
                          k,
                          ctx->segments,
                          child_keys->co,
                          ptex.effector,
                          0.0f,
                          ctx->cfra,
                          &eff_length,
                          eff_vec);
      }
      else {
        sub_v3_v3v3(eff_vec, (child + 1)->co, child->co);
        eff_length = len_v3(eff_vec);
      }
    }
  }

  {
    ParticleData *pa = nullptr;
    ParticleCacheKey *par = nullptr;
    float par_co[3];
    float par_orco[3];

    if (ctx->totparent) {
      if (i >= ctx->totparent) {
        pa = &psys->particles[cpa->parent];
        /* this is now threadsafe, virtual parents are calculated before rest of children */
        BLI_assert(cpa->parent < psys->totchildcache);
        par = cache[cpa->parent];
      }
    }
    else if (cpa->parent >= 0) {
      pa = &psys->particles[cpa->parent];
      par = pcache[cpa->parent];

      /* If particle is non-existing, try to pick a viable parent from particles
       * used for interpolation. */
      for (k = 0; k < 4 && pa && (pa->flag & PARS_UNEXIST); k++) {
        if (cpa->pa[k] >= 0) {
          pa = &psys->particles[cpa->pa[k]];
          par = pcache[cpa->pa[k]];
        }
      }

      if (pa->flag & PARS_UNEXIST) {
        pa = nullptr;
      }
    }

    if (pa) {
      ListBaseT<ModifierData> modifiers;
      modifiers.clear_no_delete();

      psys_particle_on_emitter(ctx->sim.psmd,
                               part->from,
                               pa->num,
                               pa->num_dmcache,
                               pa->fuv,
                               pa->foffset,
                               par_co,
                               nullptr,
                               nullptr,
                               nullptr,
                               par_orco);

      psys_apply_child_modifiers(
          ctx, &modifiers, cpa, &ptex, orco, hairmat, child_keys, par, par_orco);
    }
    else {
      zero_v3(par_orco);
    }
  }

  /* Hide virtual parents */
  if (i < ctx->totparent) {
    child_keys->segments = -1;
  }
}

static void exec_child_path_cache(TaskPool *__restrict /*pool*/, void *taskdata)
{
  ParticleTask *task = static_cast<ParticleTask *>(taskdata);
  ParticleThreadContext *ctx = task->ctx;
  ParticleSystem *psys = ctx->sim.psys;
  ParticleCacheKey **cache = psys->childcache;
  ChildParticle *cpa;
  int i;

  cpa = psys->child + task->begin;
  for (i = task->begin; i < task->end; i++, cpa++) {
    BLI_assert(i < psys->totchildcache);
    psys_thread_create_path(task, cpa, cache[i], i);
  }
}

void psys_cache_child_paths(ParticleSimulationData *sim,
                            float cfra,
                            const bool editupdate,
                            const bool use_render_params)
{
  if (sim->psys->flag & PSYS_GLOBAL_HAIR) {
    return;
  }

  /* create a task pool for child path tasks */
  ParticleThreadContext ctx;
  if (!psys_thread_context_init_path(&ctx, sim, sim->scene, cfra, editupdate, use_render_params)) {
    return;
  }

  TaskPool *task_pool = BLI_task_pool_create(&ctx, TASK_PRIORITY_HIGH);
  const int totchild = ctx.totchild;
  const int totparent = ctx.totparent;

  if (editupdate && sim->psys->childcache && totchild == sim->psys->totchildcache) {
    /* just overwrite the existing cache */
  }
  else {
    /* clear out old and create new empty path cache */
    free_child_path_cache(sim->psys);

    sim->psys->childcache = psys_alloc_path_cache_buffers(
        &sim->psys->childcachebufs, totchild, ctx.segments + ctx.extra_segments + 1);
    sim->psys->totchildcache = totchild;
  }

  /* cache parent paths */
  ctx.parent_pass = 1;
  Vector<ParticleTask> tasks_parent = psys_tasks_create(&ctx, 0, totparent);
  for (ParticleTask &task : tasks_parent) {
    psys_task_init_path(&task, sim);
    BLI_task_pool_push(task_pool, exec_child_path_cache, &task, false, nullptr);
  }
  BLI_task_pool_work_and_wait(task_pool);

  /* cache child paths */
  ctx.parent_pass = 0;
  Vector<ParticleTask> tasks_child = psys_tasks_create(&ctx, totparent, totchild);
  for (ParticleTask &task : tasks_child) {
    psys_task_init_path(&task, sim);
    BLI_task_pool_push(task_pool, exec_child_path_cache, &task, false, nullptr);
  }
  BLI_task_pool_work_and_wait(task_pool);

  BLI_task_pool_free(task_pool);

  psys_tasks_free(tasks_parent);
  psys_tasks_free(tasks_child);

  psys_thread_context_free(&ctx);
}

/* figure out incremental rotations along path starting from unit quat */
static void cache_key_incremental_rotation(ParticleCacheKey *key0,
                                           ParticleCacheKey *key1,
                                           ParticleCacheKey *key2,
                                           float *prev_tangent,
                                           int i)
{
  float cosangle, angle, tangent[3], normal[3], q[4];

  switch (i) {
    case 0:
      /* start from second key */
      break;
    case 1:
      /* calculate initial tangent for incremental rotations */
      sub_v3_v3v3(prev_tangent, key0->co, key1->co);
      normalize_v3(prev_tangent);
      unit_qt(key1->rot);
      break;
    default:
      sub_v3_v3v3(tangent, key0->co, key1->co);
      normalize_v3(tangent);

      cosangle = dot_v3v3(tangent, prev_tangent);

      /* note we do the comparison on cosangle instead of
       * angle, since floating point accuracy makes it give
       * different results across platforms */
      if (cosangle > 0.999999f) {
        copy_v4_v4(key1->rot, key2->rot);
      }
      else {
        angle = safe_acosf(cosangle);
        cross_v3_v3v3(normal, prev_tangent, tangent);
        axis_angle_to_quat(q, normal, angle);
        mul_qt_qtqt(key1->rot, q, key2->rot);
      }

      copy_v3_v3(prev_tangent, tangent);
  }
}

void psys_cache_paths(ParticleSimulationData *sim, float cfra, const bool use_render_params)
{
  PARTICLE_PSMD;
  ParticleEditSettings *pset = &sim->scene->toolsettings->particle;
  ParticleSystem *psys = sim->psys;
  ParticleSettings *part = psys->part;
  ParticleCacheKey *ca, **cache;

  Mesh *hair_mesh = (psys->part->type == PART_HAIR && psys->flag & PSYS_HAIR_DYNAMICS) ?
                        psys->hair_out_mesh :
                        nullptr;

  ParticleKey result;

  Material *ma;
  ParticleInterpolationData pind;
  ParticleTexture ptex;

  PARTICLE_P;

  float birthtime = 0.0, dietime = 0.0;
  float t, time = 0.0, dfra = 1.0;
  float col[4] = {0.5f, 0.5f, 0.5f, 1.0f};
  float prev_tangent[3] = {0.0f, 0.0f, 0.0f}, hairmat[4][4];
  float rotmat[3][3];
  int k;
  int segments = int(pow(2.0, double((use_render_params) ? part->ren_step : part->draw_step)));
  int totpart = psys->totpart;
  float length, vec[3];
  float *vg_effector = nullptr;
  float *vg_length = nullptr, pa_length = 1.0f;
  int keyed, baked;

  /* we don't have anything valid to create paths from so let's quit here */
  if ((psys->flag & PSYS_HAIR_DONE || psys->flag & PSYS_KEYED || psys->pointcache) == 0) {
    return;
  }

  if (psys_in_edit_mode(sim->depsgraph, psys)) {
    if ((psys->edit == nullptr || pset->flag & PE_DRAW_PART) == 0) {
      return;
    }
  }

  keyed = psys->flag & PSYS_KEYED;
  baked = psys->pointcache->mem_cache.first && psys->part->type != PART_HAIR;

  /* clear out old and create new empty path cache */
  psys_free_path_cache(psys, psys->edit);
  cache = psys->pathcache = psys_alloc_path_cache_buffers(
      &psys->pathcachebufs, totpart, segments + 1);

  psys_sim_data_init(sim);
  ma = BKE_object_material_get(sim->ob, psys->part->omat);
  if (ma && (psys->part->draw_col == PART_DRAW_COL_MAT)) {
    copy_v3_v3(col, &ma->r);
  }

  if ((psys->flag & PSYS_GLOBAL_HAIR) == 0) {
    if ((psys->part->flag & PART_CHILD_EFFECT) == 0) {
      vg_effector = psys_cache_vgroup(psmd->mesh_final, psys, PSYS_VG_EFFECTOR);
    }

    if (!psys->totchild) {
      vg_length = psys_cache_vgroup(psmd->mesh_final, psys, PSYS_VG_LENGTH);
    }
  }

  /* ensure we have tessfaces to be used for mapping */
  if (part->from != PART_FROM_VERT) {
    BKE_mesh_tessface_ensure(psmd->mesh_final);
  }

  /*---first main loop: create all actual particles' paths---*/
  LOOP_PARTICLES
  {
    if (!psys->totchild) {
      psys_get_texture(sim, pa, &ptex, PAMAP_LENGTH, 0.0f);
      pa_length = ptex.length * (1.0f - part->randlength * psys_frand(psys, psys->seed + p));
      if (vg_length) {
        pa_length *= psys_particle_value_from_verts(psmd->mesh_final, part->from, pa, vg_length);
      }
    }

    pind.keyed = keyed;
    pind.cache = baked ? psys->pointcache : nullptr;
    pind.epoint = nullptr;
    pind.bspline = (psys->part->flag & PART_HAIR_BSPLINE);
    pind.mesh = hair_mesh;

    memset(cache[p], 0, sizeof(*cache[p]) * (segments + 1));

    cache[p]->segments = segments;

    /*--get the first data points--*/
    init_particle_interpolation(sim->ob, sim->psys, pa, &pind);

    /* 'hairmat' is needed for non-hair particle too so we get proper rotations. */
    psys_mat_hair_to_global(sim->ob, psmd->mesh_final, psys->part->from, pa, hairmat);
    copy_v3_v3(rotmat[0], hairmat[2]);
    copy_v3_v3(rotmat[1], hairmat[1]);
    copy_v3_v3(rotmat[2], hairmat[0]);

    if (part->draw & PART_ABS_PATH_TIME) {
      birthtime = std::max(pind.birthtime, part->path_start);
      dietime = std::min(pind.dietime, part->path_end);
    }
    else {
      float tb = pind.birthtime;
      birthtime = tb + part->path_start * (pind.dietime - tb);
      dietime = tb + part->path_end * (pind.dietime - tb);
    }

    if (birthtime >= dietime) {
      cache[p]->segments = -1;
      continue;
    }

    dietime = birthtime + pa_length * (dietime - birthtime);

    /*--interpolate actual path from data points--*/
    for (k = 0, ca = cache[p]; k <= segments; k++, ca++) {
      time = float(k) / float(segments);
      t = birthtime + time * (dietime - birthtime);
      result.time = -t;
      do_particle_interpolation(psys, p, pa, t, &pind, &result);
      copy_v3_v3(ca->co, result.co);

      /* dynamic hair is in object space */
      /* keyed and baked are already in global space */
      if (hair_mesh) {
        mul_m4_v3(sim->ob->object_to_world().ptr(), ca->co);
      }
      else if (!keyed && !baked && !(psys->flag & PSYS_GLOBAL_HAIR)) {
        mul_m4_v3(hairmat, ca->co);
      }

      copy_v3_v3(ca->col, col);
    }

    if (part->type == PART_HAIR) {
      HairKey *hkey;

      for (k = 0, hkey = pa->hair; k < pa->totkey; k++, hkey++) {
        mul_v3_m4v3(hkey->world_co, hairmat, hkey->co);
      }
    }

    /*--modify paths and calculate rotation & velocity--*/

    if (!(psys->flag & PSYS_GLOBAL_HAIR)) {
      /* apply effectors */
      if ((psys->part->flag & PART_CHILD_EFFECT) == 0) {
        float effector = 1.0f;
        if (vg_effector) {
          effector *= psys_particle_value_from_verts(
              psmd->mesh_final, psys->part->from, pa, vg_effector);
        }

        sub_v3_v3v3(vec, (cache[p] + 1)->co, cache[p]->co);
        length = len_v3(vec);

        for (k = 1, ca = cache[p] + 1; k <= segments; k++, ca++) {
          do_path_effectors(
              sim, p, ca, k, segments, cache[p]->co, effector, dfra, cfra, &length, vec);
        }
      }

      /* apply guide curves to path data */
      if (sim->psys->effectors && (psys->part->flag & PART_CHILD_EFFECT) == 0) {
        for (k = 0, ca = cache[p]; k <= segments; k++, ca++) {
          /* ca is safe to cast, since only co and vel are used */
          do_guides(sim->depsgraph,
                    sim->psys->part,
                    sim->psys->effectors,
                    reinterpret_cast<ParticleKey *>(ca),
                    p,
                    float(k) / float(segments));
        }
      }

      /* Lattices have to be calculated separately to avoid mix-ups between effector calculations.
       */
      if (psys->lattice_deform_data) {
        for (k = 0, ca = cache[p]; k <= segments; k++, ca++) {
          BKE_lattice_deform_data_eval_co(
              psys->lattice_deform_data, ca->co, psys->lattice_strength);
        }
      }
    }

    /* finally do rotation & velocity */
    for (k = 1, ca = cache[p] + 1; k <= segments; k++, ca++) {
      cache_key_incremental_rotation(ca, ca - 1, ca - 2, prev_tangent, k);

      if (k == segments) {
        copy_qt_qt(ca->rot, (ca - 1)->rot);
      }

      /* set velocity */
      sub_v3_v3v3(ca->vel, ca->co, (ca - 1)->co);

      if (k == 1) {
        copy_v3_v3((ca - 1)->vel, ca->vel);
      }

      ca->time = float(k) / float(segments);
    }
    /* First rotation is based on emitting face orientation.
     * This is way better than having flipping rotations resulting
     * from using a global axis as a rotation pole (vec_to_quat()).
     * It's not an ideal solution though since it disregards the
     * initial tangent, but taking that in to account will allow
     * the possibility of flipping again. -jahka
     */
    mat3_to_quat_legacy(cache[p]->rot, rotmat);
  }

  psys->totcached = totpart;

  psys_sim_data_free(sim);

  if (vg_effector) {
    MEM_delete(vg_effector);
  }

  if (vg_length) {
    MEM_delete(vg_length);
  }
}

struct CacheEditrPathsIterData {
  Object *object;
  PTCacheEdit *edit;
  ParticleSystemModifierData *psmd;
  ParticleData *pa;
  int segments;
  bool use_weight;
};

static void psys_cache_edit_paths_iter(void *__restrict iter_data_v,
                                       const int iter,
                                       const TaskParallelTLS *__restrict /*tls*/)
{
  CacheEditrPathsIterData *iter_data = static_cast<CacheEditrPathsIterData *>(iter_data_v);
  PTCacheEdit *edit = iter_data->edit;
  PTCacheEditPoint *point = &edit->points[iter];
  if (edit->totcached && !(point->flag & PEP_EDIT_RECALC)) {
    return;
  }
  if (point->totkey == 0) {
    return;
  }
  Object *ob = iter_data->object;
  ParticleSystem *psys = edit->psys;
  ParticleCacheKey **cache = edit->pathcache;
  ParticleSystemModifierData *psmd = iter_data->psmd;
  ParticleData *pa = iter_data->pa ? iter_data->pa + iter : nullptr;
  PTCacheEditKey *ekey = point->keys;
  const int segments = iter_data->segments;
  const bool use_weight = iter_data->use_weight;

  float birthtime = 0.0f, dietime = 0.0f;
  float hairmat[4][4], rotmat[3][3], prev_tangent[3] = {0.0f, 0.0f, 0.0f};

  ParticleInterpolationData pind;
  pind.keyed = 0;
  pind.cache = nullptr;
  pind.epoint = point;
  pind.bspline = psys ? (psys->part->flag & PART_HAIR_BSPLINE) : 0;
  pind.mesh = nullptr;

  /* should init_particle_interpolation set this ? */
  if (use_weight) {
    pind.hkey[0] = nullptr;
    /* pa != nullptr since the weight brush is only available for hair */
    pind.hkey[0] = pa->hair;
    pind.hkey[1] = pa->hair + 1;
  }

  memset(cache[iter], 0, sizeof(*cache[iter]) * (segments + 1));

  cache[iter]->segments = segments;

  /*--get the first data points--*/
  init_particle_interpolation(ob, psys, pa, &pind);

  if (psys) {
    psys_mat_hair_to_global(ob, psmd->mesh_final, psys->part->from, pa, hairmat);
    copy_v3_v3(rotmat[0], hairmat[2]);
    copy_v3_v3(rotmat[1], hairmat[1]);
    copy_v3_v3(rotmat[2], hairmat[0]);
  }

  birthtime = pind.birthtime;
  dietime = pind.dietime;

  if (birthtime >= dietime) {
    cache[iter]->segments = -1;
    return;
  }

  /*--interpolate actual path from data points--*/
  ParticleCacheKey *ca;
  int k;
  float t, time = 0.0f, keytime = 0.0f;
  for (k = 0, ca = cache[iter]; k <= segments; k++, ca++) {
    time = float(k) / float(segments);
    t = birthtime + time * (dietime - birthtime);
    ParticleKey result;
    result.time = -t;
    do_particle_interpolation(psys, iter, pa, t, &pind, &result);
    copy_v3_v3(ca->co, result.co);

    /* non-hair points are already in global space */
    if (psys && !(psys->flag & PSYS_GLOBAL_HAIR)) {
      mul_m4_v3(hairmat, ca->co);

      if (k) {
        cache_key_incremental_rotation(ca, ca - 1, ca - 2, prev_tangent, k);

        if (k == segments) {
          copy_qt_qt(ca->rot, (ca - 1)->rot);
        }

        /* set velocity */
        sub_v3_v3v3(ca->vel, ca->co, (ca - 1)->co);

        if (k == 1) {
          copy_v3_v3((ca - 1)->vel, ca->vel);
        }
      }
    }
    else {
      ca->vel[0] = ca->vel[1] = 0.0f;
      ca->vel[2] = 1.0f;
    }

    /* selection coloring in edit mode */
    if (use_weight) {
      if (k == 0) {
        BKE_defvert_weight_to_rgb(ca->col, pind.hkey[1]->weight);
      }
      else {
        /* WARNING: copied from 'do_particle_interpolation' (without 'vertex' array stepping) */
        float real_t;
        if (result.time < 0.0f) {
          real_t = -result.time;
        }
        else {
          real_t = pind.hkey[0]->time +
                   t * (pind.hkey[0][pa->totkey - 1].time - pind.hkey[0]->time);
        }

        while (pind.hkey[1]->time < real_t) {
          pind.hkey[1]++;
        }
        pind.hkey[0] = pind.hkey[1] - 1;
        /* end copy */

        float w1[3], w2[3];
        keytime = (t - (*pind.ekey[0]->time)) / ((*pind.ekey[1]->time) - (*pind.ekey[0]->time));

        BKE_defvert_weight_to_rgb(w1, pind.hkey[0]->weight);
        BKE_defvert_weight_to_rgb(w2, pind.hkey[1]->weight);

        interp_v3_v3v3(ca->col, w1, w2, keytime);
      }
    }
    else {
      /* HACK(fclem): Instead of setting the color we pass the select state in the red channel.
       * This is then picked up in DRW and the gpu shader will do the color interpolation. */
      if ((ekey + (pind.ekey[0] - point->keys))->flag & PEK_SELECT) {
        if ((ekey + (pind.ekey[1] - point->keys))->flag & PEK_SELECT) {
          ca->col[0] = 1.0f;
        }
        else {
          keytime = (t - (*pind.ekey[0]->time)) / ((*pind.ekey[1]->time) - (*pind.ekey[0]->time));
          ca->col[0] = 1.0f - keytime;
        }
      }
      else {
        if ((ekey + (pind.ekey[1] - point->keys))->flag & PEK_SELECT) {
          keytime = (t - (*pind.ekey[0]->time)) / ((*pind.ekey[1]->time) - (*pind.ekey[0]->time));
          ca->col[0] = keytime;
        }
        else {
          ca->col[0] = 0.0f;
        }
      }
    }

    ca->time = t;
  }
  if (psys && !(psys->flag & PSYS_GLOBAL_HAIR)) {
    /* First rotation is based on emitting face orientation.
     * This is way better than having flipping rotations resulting
     * from using a global axis as a rotation pole (vec_to_quat()).
     * It's not an ideal solution though since it disregards the
     * initial tangent, but taking that in to account will allow
     * the possibility of flipping again. -jahka
     */
    mat3_to_quat_legacy(cache[iter]->rot, rotmat);
  }
}

void psys_cache_edit_paths(Depsgraph *depsgraph,
                           Scene *scene,
                           Object *ob,
                           PTCacheEdit *edit,
                           float cfra,
                           const bool use_render_params)
{
  ParticleCacheKey **cache = edit->pathcache;
  ParticleEditSettings *pset = &scene->toolsettings->particle;

  ParticleSystem *psys = edit->psys;

  ParticleData *pa = psys ? psys->particles : nullptr;

  int segments = 1 << pset->draw_step;
  int totpart = edit->totpoint, recalc_set = 0;

  if (edit->psmd_eval == nullptr) {
    return;
  }

  segments = std::max(segments, 4);

  if (!cache || edit->totpoint != edit->totcached) {
    /* Clear out old and create new empty path cache. */
    psys_free_path_cache(edit->psys, edit);
    cache = edit->pathcache = psys_alloc_path_cache_buffers(
        &edit->pathcachebufs, totpart, segments + 1);
    /* Set flag for update (child particles check this too). */
    int i;
    PTCacheEditPoint *point;
    for (i = 0, point = edit->points; i < totpart; i++, point++) {
      point->flag |= PEP_EDIT_RECALC;
    }
    recalc_set = 1;
  }

  const bool use_weight = (pset->brushtype == PE_BRUSH_WEIGHT) && (psys != nullptr) &&
                          (psys->particles != nullptr);

  CacheEditrPathsIterData iter_data;
  iter_data.object = ob;
  iter_data.edit = edit;
  iter_data.psmd = edit->psmd_eval;
  iter_data.pa = pa;
  iter_data.segments = segments;
  iter_data.use_weight = use_weight;

  TaskParallelSettings settings;
  BLI_parallel_range_settings_defaults(&settings);
  BLI_task_parallel_range(0, edit->totpoint, &iter_data, psys_cache_edit_paths_iter, &settings);

  edit->totcached = totpart;

  if (psys) {
    ParticleSimulationData sim = {nullptr};
    sim.depsgraph = depsgraph;
    sim.scene = scene;
    sim.ob = ob;
    sim.psys = psys;
    sim.psmd = edit->psmd_eval;

    psys_cache_child_paths(&sim, cfra, true, use_render_params);
  }

  /* clear recalc flag if set here */
  if (recalc_set) {
    PTCacheEditPoint *point;
    int i;
    for (i = 0, point = edit->points; i < totpart; i++, point++) {
      point->flag &= ~PEP_EDIT_RECALC;
    }
  }
}

/** \} */

/* -------------------------------------------------------------------- */
/** \name Particle Key Handling
 * \{ */

void copy_particle_key(ParticleKey *to, ParticleKey *from, int time)
{
  if (time) {
    memcpy(to, from, sizeof(ParticleKey));
  }
  else {
    float to_time = to->time;
    memcpy(to, from, sizeof(ParticleKey));
    to->time = to_time;
  }
}
void psys_get_from_key(ParticleKey *key, float loc[3], float vel[3], float rot[4], float *time)
{
  if (loc) {
    copy_v3_v3(loc, key->co);
  }
  if (vel) {
    copy_v3_v3(vel, key->vel);
  }
  if (rot) {
    copy_qt_qt(rot, key->rot);
  }
  if (time) {
    *time = key->time;
  }
}

static void triatomat(float *v1, float *v2, float *v3, const float (*uv)[2], float mat[4][4])
{
  float det, w1, w2, d1[2], d2[2];

  memset(mat, 0, sizeof(float[4][4]));
  mat[3][3] = 1.0f;

  /* first axis is the normal */
  normal_tri_v3(mat[2], v1, v2, v3);

  /* second axis along (1, 0) in uv space */
  if (uv) {
    d1[0] = uv[1][0] - uv[0][0];
    d1[1] = uv[1][1] - uv[0][1];
    d2[0] = uv[2][0] - uv[0][0];
    d2[1] = uv[2][1] - uv[0][1];

    det = d2[0] * d1[1] - d2[1] * d1[0];

    if (det != 0.0f) {
      det = 1.0f / det;
      w1 = -d2[1] * det;
      w2 = d1[1] * det;

      mat[1][0] = w1 * (v2[0] - v1[0]) + w2 * (v3[0] - v1[0]);
      mat[1][1] = w1 * (v2[1] - v1[1]) + w2 * (v3[1] - v1[1]);
      mat[1][2] = w1 * (v2[2] - v1[2]) + w2 * (v3[2] - v1[2]);
      normalize_v3(mat[1]);
    }
    else {
      mat[1][0] = mat[1][1] = mat[1][2] = 0.0f;
    }
  }
  else {
    sub_v3_v3v3(mat[1], v2, v1);
    normalize_v3(mat[1]);
  }

  /* third as a cross product */
  cross_v3_v3v3(mat[0], mat[1], mat[2]);
}

static void psys_face_mat(Object *ob, Mesh *mesh, ParticleData *pa, float mat[4][4], int orco)
{
  float v[3][3];
  MFace *mface;
  const float (*orcodata)[3];

  int i = ELEM(pa->num_dmcache, DMCACHE_ISCHILD, DMCACHE_NOTFOUND) ? pa->num : pa->num_dmcache;
  if (i == -1 || i >= mesh->totface_legacy) {
    unit_m4(mat);
    return;
  }

  MFace *mfaces = static_cast<MFace *>(
      CustomData_get_layer_for_write(&mesh->fdata_legacy, CD_MFACE, mesh->totface_legacy));
  mface = &mfaces[i];
  const OrigSpaceFace *osface = static_cast<const OrigSpaceFace *>(
      CustomData_get_for_write(&mesh->fdata_legacy, i, CD_ORIGSPACE, mesh->totface_legacy));

  if (orco && (orcodata = static_cast<const float (*)[3]>(
                   CustomData_get_layer(&mesh->vert_data, CD_ORCO))))
  {
    copy_v3_v3(v[0], orcodata[mface->v1]);
    copy_v3_v3(v[1], orcodata[mface->v2]);
    copy_v3_v3(v[2], orcodata[mface->v3]);

    /* ugly hack to use non-transformed orcos, since only those
     * give symmetric results for mirroring in particle mode */
    if (CustomData_get_layer(&mesh->vert_data, CD_ORIGINDEX)) {
      BKE_mesh_orco_verts_transform(id_cast<Mesh *>(ob->data), v, 3, true);
    }
  }
  else {
    const Span<float3> vert_positions = mesh->vert_positions();
    copy_v3_v3(v[0], vert_positions[mface->v1]);
    copy_v3_v3(v[1], vert_positions[mface->v2]);
    copy_v3_v3(v[2], vert_positions[mface->v3]);
  }

  triatomat(v[0], v[1], v[2], (osface) ? osface->uv : nullptr, mat);
}

void psys_mat_hair_to_object(
    Object * /*ob*/, Mesh *mesh, short from, ParticleData *pa, float hairmat[4][4])
{
  float vec[3];

  /* can happen when called from a different object's modifier */
  if (!mesh) {
    unit_m4(hairmat);
    return;
  }

  psys_face_mat(nullptr, mesh, pa, hairmat, 0);
  psys_particle_on_dm(mesh,
                      from,
                      pa->num,
                      pa->num_dmcache,
                      pa->fuv,
                      pa->foffset,
                      vec,
                      nullptr,
                      nullptr,
                      nullptr,
                      nullptr);
  copy_v3_v3(hairmat[3], vec);
}

void psys_mat_hair_to_orco(
    Object *ob, Mesh *mesh, short from, ParticleData *pa, float hairmat[4][4])
{
  float vec[3], orco[3];

  psys_face_mat(ob, mesh, pa, hairmat, 1);
  psys_particle_on_dm(mesh,
                      from,
                      pa->num,
                      pa->num_dmcache,
                      pa->fuv,
                      pa->foffset,
                      vec,
                      nullptr,
                      nullptr,
                      nullptr,
                      orco);

  copy_v3_v3(hairmat[3], orco);
}

void psys_vec_rot_to_face(Mesh *mesh, ParticleData *pa, float vec[3])
{
  float mat[4][4];

  psys_face_mat(nullptr, mesh, pa, mat, 0);
  transpose_m4(mat); /* cheap inverse for rotation matrix */
  mul_mat3_m4_v3(mat, vec);
}

void psys_mat_hair_to_global(
    Object *ob, Mesh *mesh, short from, ParticleData *pa, float hairmat[4][4])
{
  float facemat[4][4];

  psys_mat_hair_to_object(ob, mesh, from, pa, facemat);

  mul_m4_m4m4(hairmat, ob->object_to_world().ptr(), facemat);
}

/** \} */

/* -------------------------------------------------------------------- */
/** \name ParticleSettings Handling
 * \{ */

static ModifierData *object_add_or_copy_particle_system(
    Main *bmain, const Scene *scene, Object *ob, const char *name, const ParticleSystem *psys_orig)
{
  ParticleSystem *psys;
  ModifierData *md;
  ParticleSystemModifierData *psmd;

  if (!ob || ob->type != OB_MESH) {
    return nullptr;
  }

  if (name == nullptr) {
    name = (psys_orig != nullptr) ? psys_orig->name : DATA_("ParticleSystem");
  }

  psys = static_cast<ParticleSystem *>(ob->particlesystem.first);
  for (; psys; psys = psys->next) {
    psys->flag &= ~PSYS_CURRENT;
  }

  psys = MEM_new<ParticleSystem>("particle_system");
  psys->pointcache = BKE_ptcache_add(&psys->ptcaches);
  BLI_addtail(&ob->particlesystem, psys);
  psys_unique_name(ob, psys, name);

  if (psys_orig != nullptr) {
    psys->part = psys_orig->part;
    id_us_plus(&psys->part->id);
  }
  else {
    psys->part = BKE_particlesettings_add(bmain, DATA_("ParticleSettings"));
  }
  md = BKE_modifier_new(eModifierType_ParticleSystem);
  STRNCPY_UTF8(md->name, psys->name);
  BKE_modifier_unique_name(&ob->modifiers, md);

  psmd = reinterpret_cast<ParticleSystemModifierData *>(md);
  psmd->psys = psys;

  BKE_modifiers_add_at_end_if_possible(ob, md);
  BKE_object_modifier_set_active(ob, md);
  BKE_modifiers_persistent_uid_init(*ob, *md);

  psys->totpart = 0;
  psys->flag = PSYS_CURRENT;
  if (scene != nullptr) {
    psys->cfra = BKE_scene_frame_to_ctime(scene, scene->r.cfra + 1);
  }

  DEG_relations_tag_update(bmain);
  DEG_id_tag_update(&ob->id, ID_RECALC_GEOMETRY);

  return md;
}

ModifierData *object_add_particle_system(Main *bmain,
                                         const Scene *scene,
                                         Object *ob,
                                         const char *name)
{
  return object_add_or_copy_particle_system(bmain, scene, ob, name, nullptr);
}

ModifierData *object_copy_particle_system(Main *bmain,
                                          const Scene *scene,
                                          Object *ob,
                                          const ParticleSystem *psys_orig)
{
  return object_add_or_copy_particle_system(bmain, scene, ob, nullptr, psys_orig);
}

void object_remove_particle_system(Main *bmain,
                                   Scene * /*scene*/,
                                   Object *ob,
                                   ParticleSystem *psys)
{
  if (!ob || !psys) {
    return;
  }

  ParticleSystemModifierData *psmd;
  ModifierData *md = BKE_modifiers_findby_type(ob, eModifierType_Fluid);

  /* Clear particle system in fluid modifier. */
  if (md) {
    FluidModifierData *fmd = reinterpret_cast<FluidModifierData *>(md);

    /* Clear particle system pointer in flow settings. */
    if ((fmd->type == MOD_FLUID_TYPE_FLOW) && fmd->flow && fmd->flow->psys) {
      if (fmd->flow->psys == psys) {
        fmd->flow->psys = nullptr;
      }
    }
    /* Clear particle flag in domain settings when removing particle system manually. */
    if (fmd->type == MOD_FLUID_TYPE_DOMAIN) {
      if (psys->part->type == PART_FLUID_FLIP) {
        fmd->domain->particle_type &= ~FLUID_DOMAIN_PARTICLE_FLIP;
      }
      if (ELEM(psys->part->type,
               PART_FLUID_SPRAY,
               PART_FLUID_SPRAYFOAM,
               PART_FLUID_SPRAYBUBBLE,
               PART_FLUID_SPRAYFOAMBUBBLE))
      {
        fmd->domain->particle_type &= ~FLUID_DOMAIN_PARTICLE_SPRAY;
      }
      if (ELEM(psys->part->type,
               PART_FLUID_FOAM,
               PART_FLUID_SPRAYFOAM,
               PART_FLUID_FOAMBUBBLE,
               PART_FLUID_SPRAYFOAMBUBBLE))
      {
        fmd->domain->particle_type &= ~FLUID_DOMAIN_PARTICLE_FOAM;
      }
      if (ELEM(psys->part->type,
               PART_FLUID_BUBBLE,
               PART_FLUID_FOAMBUBBLE,
               PART_FLUID_SPRAYBUBBLE,
               PART_FLUID_SPRAYFOAMBUBBLE))
      {
        fmd->domain->particle_type &= ~FLUID_DOMAIN_PARTICLE_BUBBLE;
      }
      if (psys->part->type == PART_FLUID_TRACER) {
        fmd->domain->particle_type &= ~FLUID_DOMAIN_PARTICLE_TRACER;
      }

      /* Disable combined export if combined particle system was deleted. */
      if (ELEM(psys->part->type,
               PART_FLUID_SPRAYFOAM,
               PART_FLUID_SPRAYBUBBLE,
               PART_FLUID_FOAMBUBBLE,
               PART_FLUID_SPRAYFOAMBUBBLE))
      {
        fmd->domain->sndparticle_combined_export = SNDPARTICLE_COMBINED_EXPORT_OFF;
      }
    }
  }

  if ((md = BKE_modifiers_findby_type(ob, eModifierType_DynamicPaint))) {
    DynamicPaintModifierData *pmd = reinterpret_cast<DynamicPaintModifierData *>(md);
    if (pmd->brush && pmd->brush->psys) {
      if (pmd->brush->psys == psys) {
        pmd->brush->psys = nullptr;
      }
    }
  }

  /* Clear modifier, skip empty ones. */
  psmd = psys_get_modifier(ob, psys);
  if (psmd) {
    BKE_modifier_remove_from_list(ob, reinterpret_cast<ModifierData *>(psmd));
    BKE_modifier_free(reinterpret_cast<ModifierData *>(psmd));
  }

  /* Clear particle system. */
  BLI_remlink(&ob->particlesystem, psys);
  if (psys->part) {
    id_us_min(&psys->part->id);
  }
  psys_free(ob, psys);

  if (ob->particlesystem.first) {
    (static_cast<ParticleSystem *>(ob->particlesystem.first))->flag |= PSYS_CURRENT;
  }
  else {
    ob->mode &= ~OB_MODE_PARTICLE_EDIT;
  }

  DEG_relations_tag_update(bmain);
  DEG_id_tag_update(&ob->id, ID_RECALC_GEOMETRY);

  /* Flush object mode. */
  DEG_id_tag_update(&ob->id, ID_RECALC_SYNC_TO_EVAL);
}

ParticleSettings *BKE_particlesettings_add(Main *bmain, const char *name)
{
  ParticleSettings *part;

  part = BKE_id_new<ParticleSettings>(bmain, name);

  return part;
}

void BKE_particlesettings_clump_curve_init(ParticleSettings *part)
{
  CurveMapping *cumap = BKE_curvemapping_add(1, 0.0f, 0.0f, 1.0f, 1.0f);

  cumap->cm[0].curve[0].x = 0.0f;
  cumap->cm[0].curve[0].y = 1.0f;
  cumap->cm[0].curve[1].x = 1.0f;
  cumap->cm[0].curve[1].y = 1.0f;

  BKE_curvemapping_init(cumap);

  part->clumpcurve = cumap;
}

void BKE_particlesettings_rough_curve_init(ParticleSettings *part)
{
  CurveMapping *cumap = BKE_curvemapping_add(1, 0.0f, 0.0f, 1.0f, 1.0f);

  cumap->cm[0].curve[0].x = 0.0f;
  cumap->cm[0].curve[0].y = 1.0f;
  cumap->cm[0].curve[1].x = 1.0f;
  cumap->cm[0].curve[1].y = 1.0f;

  BKE_curvemapping_init(cumap);

  part->roughcurve = cumap;
}

void BKE_particlesettings_twist_curve_init(ParticleSettings *part)
{
  CurveMapping *cumap = BKE_curvemapping_add(1, 0.0f, 0.0f, 1.0f, 1.0f);

  cumap->cm[0].curve[0].x = 0.0f;
  cumap->cm[0].curve[0].y = 1.0f;
  cumap->cm[0].curve[1].x = 1.0f;
  cumap->cm[0].curve[1].y = 1.0f;

  BKE_curvemapping_init(cumap);

  part->twistcurve = cumap;
}

/** \} */

/* -------------------------------------------------------------------- */
/** \name Textures
 * \{ */

static int get_particle_uv(Mesh *mesh,
                           ParticleData *pa,
                           int index,
                           const float fuv[4],
                           const char *name,
                           float *texco,
                           bool from_vert)
{
  MFace *mfaces = static_cast<MFace *>(
      CustomData_get_layer_for_write(&mesh->fdata_legacy, CD_MFACE, mesh->totface_legacy));
  MFace *mf;
  const MTFace *tf;
  int i;

  tf = static_cast<const MTFace *>(
      CustomData_get_layer_named(&mesh->fdata_legacy, CD_MTFACE, name));
  if (tf == nullptr) {
    tf = static_cast<const MTFace *>(CustomData_get_layer(&mesh->fdata_legacy, CD_MTFACE));
  }
  if (tf == nullptr) {
    return 0;
  }

  if (pa) {
    i = ELEM(pa->num_dmcache, DMCACHE_NOTFOUND, DMCACHE_ISCHILD) ? pa->num : pa->num_dmcache;
    if ((!from_vert && i >= mesh->totface_legacy) || (from_vert && i >= mesh->verts_num)) {
      i = -1;
    }
  }
  else {
    i = index;
  }

  if (i == -1) {
    texco[0] = 0.0f;
    texco[1] = 0.0f;
    texco[2] = 0.0f;
  }
  else {
    if (from_vert) {
      mf = mfaces;

      /* This finds the first face to contain the emitting vertex,
       * this is not ideal, but is mostly fine as UV seams generally
       * map to equal-colored parts of a texture */
      for (int j = 0; j < mesh->totface_legacy; j++, mf++) {
        if (ELEM(i, mf->v1, mf->v2, mf->v3, mf->v4)) {
          i = j;
          break;
        }
      }
    }
    else {
      mf = &mfaces[i];
    }

    psys_interpolate_uvs(&tf[i], mf->v4, fuv, texco);

    texco[0] = texco[0] * 2.0f - 1.0f;
    texco[1] = texco[1] * 2.0f - 1.0f;
    texco[2] = 0.0f;
  }

  return 1;
}

#define SET_PARTICLE_TEXTURE(type, pvalue, texfac) \
  if ((event & mtex->mapto) & type) { \
    pvalue = texture_value_blend(def, pvalue, value, texfac, blend); \
  } \
  (void)0

#define CLAMP_PARTICLE_TEXTURE_POS(type, pvalue) \
  if (event & type) { \
    CLAMP(pvalue, 0.0f, 1.0f); \
  } \
  (void)0

#define CLAMP_WARP_PARTICLE_TEXTURE_POS(type, pvalue) \
  if (event & type) { \
    if (pvalue < 0.0f) { \
      pvalue = 1.0f + pvalue; \
    } \
    CLAMP(pvalue, 0.0f, 1.0f); \
  } \
  (void)0

#define CLAMP_PARTICLE_TEXTURE_POSNEG(type, pvalue) \
  if (event & type) { \
    CLAMP(pvalue, -1.0f, 1.0f); \
  } \
  (void)0

static void get_cpa_texture(Mesh *mesh,
                            ParticleSystem *psys,
                            ParticleSettings *part,
                            ParticleData *par,
                            int child_index,
                            int face_index,
                            const float fw[4],
                            float *orco,
                            ParticleTexture *ptex,
                            int event,
                            float cfra)
{
  MTex *mtex, **mtexp = part->mtex;
  int m;
  float value, rgba[4], texvec[3];

  ptex->ivel = ptex->life = ptex->exist = ptex->size = ptex->damp = ptex->gravity = ptex->field =
      ptex->time = ptex->clump = ptex->kink_freq = ptex->kink_amp = ptex->effector = ptex->rough1 =
          ptex->rough2 = ptex->roughe = 1.0f;
  ptex->twist = 1.0f;

  ptex->length = 1.0f - part->randlength * psys_frand(psys, child_index + 26);
  ptex->length *= part->clength_thres < psys_frand(psys, child_index + 27) ? part->clength : 1.0f;

  for (m = 0; m < MAX_MTEX; m++, mtexp++) {
    mtex = *mtexp;
    if (mtex && mtex->tex && mtex->mapto) {
      float def = mtex->def_var;
      short blend = mtex->blendtype;
      short texco = mtex->texco;

      if (ELEM(texco, TEXCO_UV, TEXCO_ORCO) &&
          (ELEM(part->from, PART_FROM_FACE, PART_FROM_VOLUME) == 0 ||
           part->distr == PART_DISTR_GRID))
      {
        texco = TEXCO_GLOB;
      }

      switch (texco) {
        case TEXCO_GLOB:
          copy_v3_v3(texvec, par->state.co);
          break;
        case TEXCO_OBJECT:
          copy_v3_v3(texvec, par->state.co);
          if (mtex->object) {
            mul_m4_v3(mtex->object->world_to_object().ptr(), texvec);
          }
          break;
        case TEXCO_UV:
          if (fw && get_particle_uv(mesh,
                                    nullptr,
                                    face_index,
                                    fw,
                                    mtex->uvname,
                                    texvec,
                                    (part->from == PART_FROM_VERT)))
          {
            break;
          }
          /* no break, failed to get uv's, so let's try orco's */
          ATTR_FALLTHROUGH;
        case TEXCO_ORCO:
          copy_v3_v3(texvec, orco);
          break;
        case TEXCO_PARTICLE:
          /* texture coordinates in range [-1, 1] */
          texvec[0] = 2.0f * (cfra - par->time) / (par->dietime - par->time) - 1.0f;
          texvec[1] = 0.0f;
          texvec[2] = 0.0f;
          break;
      }

      RE_texture_evaluate(mtex, texvec, 0, nullptr, false, false, &value, rgba);

      if ((event & mtex->mapto) & PAMAP_ROUGH) {
        ptex->rough1 = ptex->rough2 = ptex->roughe = texture_value_blend(
            def, ptex->rough1, value, mtex->roughfac, blend);
      }

      SET_PARTICLE_TEXTURE(PAMAP_LENGTH, ptex->length, mtex->lengthfac);
      SET_PARTICLE_TEXTURE(PAMAP_CLUMP, ptex->clump, mtex->clumpfac);
      SET_PARTICLE_TEXTURE(PAMAP_KINK_AMP, ptex->kink_amp, mtex->kinkampfac);
      SET_PARTICLE_TEXTURE(PAMAP_KINK_FREQ, ptex->kink_freq, mtex->kinkfac);
      SET_PARTICLE_TEXTURE(PAMAP_DENS, ptex->exist, mtex->padensfac);
      SET_PARTICLE_TEXTURE(PAMAP_TWIST, ptex->twist, mtex->twistfac);
    }
  }

  CLAMP_PARTICLE_TEXTURE_POS(PAMAP_LENGTH, ptex->length);
  CLAMP_WARP_PARTICLE_TEXTURE_POS(PAMAP_CLUMP, ptex->clump);
  CLAMP_WARP_PARTICLE_TEXTURE_POS(PAMAP_KINK_AMP, ptex->kink_amp);
  CLAMP_WARP_PARTICLE_TEXTURE_POS(PAMAP_KINK_FREQ, ptex->kink_freq);
  CLAMP_WARP_PARTICLE_TEXTURE_POS(PAMAP_ROUGH, ptex->rough1);
  CLAMP_WARP_PARTICLE_TEXTURE_POS(PAMAP_DENS, ptex->exist);
}
void psys_get_texture(
    ParticleSimulationData *sim, ParticleData *pa, ParticleTexture *ptex, int event, float cfra)
{
  Object *ob = sim->ob;
  Mesh *mesh = id_cast<Mesh *>(ob->data);
  ParticleSettings *part = sim->psys->part;
  MTex **mtexp = part->mtex;
  MTex *mtex;
  int m;
  float value, rgba[4], co[3], texvec[3];
  int setvars = 0;

  /* initialize ptex */
  ptex->ivel = ptex->life = ptex->exist = ptex->size = ptex->damp = ptex->gravity = ptex->field =
      ptex->length = ptex->clump = ptex->kink_freq = ptex->kink_amp = ptex->effector =
          ptex->rough1 = ptex->rough2 = ptex->roughe = 1.0f;
  ptex->twist = 1.0f;

  ptex->time = float(pa - sim->psys->particles) / float(sim->psys->totpart);

  for (m = 0; m < MAX_MTEX; m++, mtexp++) {
    mtex = *mtexp;
    if (mtex && mtex->tex && mtex->mapto) {
      float def = mtex->def_var;
      short blend = mtex->blendtype;
      short texco = mtex->texco;

      if (texco == TEXCO_UV && (ELEM(part->from, PART_FROM_FACE, PART_FROM_VOLUME) == 0 ||
                                part->distr == PART_DISTR_GRID))
      {
        texco = TEXCO_GLOB;
      }

      switch (texco) {
        case TEXCO_GLOB:
          copy_v3_v3(texvec, pa->state.co);
          break;
        case TEXCO_OBJECT:
          copy_v3_v3(texvec, pa->state.co);
          if (mtex->object) {
            mul_m4_v3(mtex->object->world_to_object().ptr(), texvec);
          }
          break;
        case TEXCO_UV:
          if (get_particle_uv(sim->psmd->mesh_final,
                              pa,
                              0,
                              pa->fuv,
                              mtex->uvname,
                              texvec,
                              (part->from == PART_FROM_VERT)))
          {
            break;
          }
          /* no break, failed to get uv's, so let's try orco's */
          ATTR_FALLTHROUGH;
        case TEXCO_ORCO:
          psys_particle_on_emitter(sim->psmd,
                                   sim->psys->part->from,
                                   pa->num,
                                   pa->num_dmcache,
                                   pa->fuv,
                                   pa->foffset,
                                   co,
                                   nullptr,
                                   nullptr,
                                   nullptr,
                                   texvec);

          BKE_mesh_texspace_ensure(mesh);
          sub_v3_v3(texvec, mesh->texspace_location);
          if (mesh->texspace_size[0] != 0.0f) {
            texvec[0] /= mesh->texspace_size[0];
          }
          if (mesh->texspace_size[1] != 0.0f) {
            texvec[1] /= mesh->texspace_size[1];
          }
          if (mesh->texspace_size[2] != 0.0f) {
            texvec[2] /= mesh->texspace_size[2];
          }
          break;
        case TEXCO_PARTICLE:
          /* texture coordinates in range [-1, 1] */
          texvec[0] = 2.0f * (cfra - pa->time) / (pa->dietime - pa->time) - 1.0f;
          if (sim->psys->totpart > 0) {
            texvec[1] = 2.0f * float(pa - sim->psys->particles) / float(sim->psys->totpart) - 1.0f;
          }
          else {
            texvec[1] = 0.0f;
          }
          texvec[2] = 0.0f;
          break;
      }

      RE_texture_evaluate(mtex, texvec, 0, nullptr, false, false, &value, rgba);

      if ((event & mtex->mapto) & PAMAP_TIME) {
        /* the first time has to set the base value for time regardless of blend mode */
        if ((setvars & PAMAP_TIME) == 0) {
          int flip = (mtex->timefac < 0.0f);
          float timefac = fabsf(mtex->timefac);
          ptex->time *= 1.0f - timefac;
          ptex->time += timefac * ((flip) ? 1.0f - value : value);
          setvars |= PAMAP_TIME;
        }
        else {
          ptex->time = texture_value_blend(def, ptex->time, value, mtex->timefac, blend);
        }
      }
      SET_PARTICLE_TEXTURE(PAMAP_LIFE, ptex->life, mtex->lifefac);
      SET_PARTICLE_TEXTURE(PAMAP_DENS, ptex->exist, mtex->padensfac);
      SET_PARTICLE_TEXTURE(PAMAP_SIZE, ptex->size, mtex->sizefac);
      SET_PARTICLE_TEXTURE(PAMAP_IVEL, ptex->ivel, mtex->ivelfac);
      SET_PARTICLE_TEXTURE(PAMAP_FIELD, ptex->field, mtex->fieldfac);
      SET_PARTICLE_TEXTURE(PAMAP_GRAVITY, ptex->gravity, mtex->gravityfac);
      SET_PARTICLE_TEXTURE(PAMAP_DAMP, ptex->damp, mtex->dampfac);
      SET_PARTICLE_TEXTURE(PAMAP_LENGTH, ptex->length, mtex->lengthfac);
      SET_PARTICLE_TEXTURE(PAMAP_TWIST, ptex->twist, mtex->twistfac);
    }
  }

  CLAMP_WARP_PARTICLE_TEXTURE_POS(PAMAP_TIME, ptex->time);
  CLAMP_WARP_PARTICLE_TEXTURE_POS(PAMAP_LIFE, ptex->life);
  CLAMP_WARP_PARTICLE_TEXTURE_POS(PAMAP_DENS, ptex->exist);
  CLAMP_PARTICLE_TEXTURE_POS(PAMAP_SIZE, ptex->size);
  CLAMP_PARTICLE_TEXTURE_POSNEG(PAMAP_IVEL, ptex->ivel);
  CLAMP_PARTICLE_TEXTURE_POSNEG(PAMAP_FIELD, ptex->field);
  CLAMP_PARTICLE_TEXTURE_POSNEG(PAMAP_GRAVITY, ptex->gravity);
  CLAMP_WARP_PARTICLE_TEXTURE_POS(PAMAP_DAMP, ptex->damp);
  CLAMP_PARTICLE_TEXTURE_POS(PAMAP_LENGTH, ptex->length);
}

/** \} */

/* -------------------------------------------------------------------- */
/** \name Particle State
 * \{ */

float psys_get_timestep(ParticleSimulationData *sim)
{
  return 0.04f * sim->psys->part->timetweak;
}
float psys_get_child_time(
    ParticleSystem *psys, ChildParticle *cpa, float cfra, float *birthtime, float *dietime)
{
  ParticleSettings *part = psys->part;
  float time, life;

  if (part->childtype == PART_CHILD_FACES) {
    int w = 0;
    time = 0.0;
    while (w < 4 && cpa->pa[w] >= 0) {
      time += cpa->w[w] * (psys->particles + cpa->pa[w])->time;
      w++;
    }

    life = part->lifetime * (1.0f - part->randlife * psys_frand(psys, cpa - psys->child + 25));
  }
  else {
    ParticleData *pa = psys->particles + cpa->parent;

    time = pa->time;
    life = pa->lifetime;
  }

  if (birthtime) {
    *birthtime = time;
  }
  if (dietime) {
    *dietime = time + life;
  }

  return (cfra - time) / life;
}
float psys_get_child_size(ParticleSystem *psys,
                          ChildParticle *cpa,
                          float /*cfra*/,
                          float * /*pa_time*/)
{
  ParticleSettings *part = psys->part;
  float size; /* time XXX */

  if (part->childtype == PART_CHILD_FACES) {
    int w = 0;
    size = 0.0;
    while (w < 4 && cpa->pa[w] >= 0) {
      size += cpa->w[w] * (psys->particles + cpa->pa[w])->size;
      w++;
    }
  }
  else {
    size = psys->particles[cpa->parent].size;
  }

  size *= part->childsize;

  if (part->childrandsize != 0.0f) {
    size *= 1.0f - part->childrandsize * psys_frand(psys, cpa - psys->child + 26);
  }

  return size;
}
static void get_child_modifier_parameters(ParticleSettings *part,
                                          ParticleThreadContext *ctx,
                                          ChildParticle *cpa,
                                          short cpa_from,
                                          int cpa_num,
                                          float *cpa_fuv,
                                          float *orco,
                                          ParticleTexture *ptex)
{
  ParticleSystem *psys = ctx->sim.psys;
  int i = cpa - psys->child;

  get_cpa_texture(ctx->mesh,
                  psys,
                  part,
                  psys->particles + cpa->pa[0],
                  i,
                  cpa_num,
                  cpa_fuv,
                  orco,
                  ptex,
                  PAMAP_DENS | PAMAP_CHILD,
                  psys->cfra);

  if (ptex->exist < psys_frand(psys, i + 24)) {
    return;
  }

  if (ctx->vg_length) {
    ptex->length *= psys_interpolate_value_from_verts(
        ctx->mesh, cpa_from, cpa_num, cpa_fuv, ctx->vg_length);
  }
  if (ctx->vg_clump) {
    ptex->clump *= psys_interpolate_value_from_verts(
        ctx->mesh, cpa_from, cpa_num, cpa_fuv, ctx->vg_clump);
  }
  if (ctx->vg_kink) {
    ptex->kink_freq *= psys_interpolate_value_from_verts(
        ctx->mesh, cpa_from, cpa_num, cpa_fuv, ctx->vg_kink);
  }
  if (ctx->vg_rough1) {
    ptex->rough1 *= psys_interpolate_value_from_verts(
        ctx->mesh, cpa_from, cpa_num, cpa_fuv, ctx->vg_rough1);
  }
  if (ctx->vg_rough2) {
    ptex->rough2 *= psys_interpolate_value_from_verts(
        ctx->mesh, cpa_from, cpa_num, cpa_fuv, ctx->vg_rough2);
  }
  if (ctx->vg_roughe) {
    ptex->roughe *= psys_interpolate_value_from_verts(
        ctx->mesh, cpa_from, cpa_num, cpa_fuv, ctx->vg_roughe);
  }
  if (ctx->vg_effector) {
    ptex->effector *= psys_interpolate_value_from_verts(
        ctx->mesh, cpa_from, cpa_num, cpa_fuv, ctx->vg_effector);
  }
  if (ctx->vg_twist) {
    ptex->twist *= psys_interpolate_value_from_verts(
        ctx->mesh, cpa_from, cpa_num, cpa_fuv, ctx->vg_twist);
  }
}
void psys_get_particle_on_path(ParticleSimulationData *sim,
                               int p,
                               ParticleKey *state,
                               const bool vel)
{
  PARTICLE_PSMD;
  ParticleSystem *psys = sim->psys;
  ParticleSettings *part = sim->psys->part;
  Material *ma = BKE_object_material_get(sim->ob, part->omat);
  ParticleData *pa;
  ChildParticle *cpa;
  ParticleTexture ptex;
  ParticleKey *par = nullptr, tstate;
  ParticleThreadContext ctx; /* fake thread context for child modifiers */
  ParticleInterpolationData pind;

  float t;
  float co[3], orco[3];
  float hairmat[4][4];
  int totpart = psys->totpart;
  int totchild = psys->totchild;
  short between = 0, edit = 0;

  int keyed = part->phystype & PART_PHYS_KEYED && psys->flag & PSYS_KEYED;
  int cached = !keyed && part->type != PART_HAIR;

  float *cpa_fuv;
  int cpa_num;
  short cpa_from;

  /* initialize keys to zero */
  ParticleKey keys[4] = {};

  t = state->time;
  CLAMP(t, 0.0f, 1.0f);

  if (p < totpart) {
    /* interpolate pathcache directly if it exist */
    if (psys->pathcache) {
      ParticleCacheKey result;
      interpolate_pathcache(psys->pathcache[p], t, &result);
      copy_v3_v3(state->co, result.co);
      copy_v3_v3(state->vel, result.vel);
      copy_qt_qt(state->rot, result.rot);
    }
    /* otherwise interpolate with other means */
    else {
      pa = psys->particles + p;

      pind.keyed = keyed;
      pind.cache = cached ? psys->pointcache : nullptr;
      pind.epoint = nullptr;
      pind.bspline = (psys->part->flag & PART_HAIR_BSPLINE);
      /* `pind.dm` disabled in edit-mode means we don't get effectors taken into
       * account when subdividing for instance. */
      pind.mesh = psys_in_edit_mode(sim->depsgraph, psys) ?
                      nullptr :
                      psys->hair_out_mesh; /* XXX(@sybren): EEK. */
      init_particle_interpolation(sim->ob, psys, pa, &pind);
      do_particle_interpolation(psys, p, pa, t, &pind, state);

      if (pind.mesh) {
        mul_m4_v3(sim->ob->object_to_world().ptr(), state->co);
        mul_mat3_m4_v3(sim->ob->object_to_world().ptr(), state->vel);
      }
      else if (!keyed && !cached && !(psys->flag & PSYS_GLOBAL_HAIR)) {
        if ((pa->flag & PARS_REKEY) == 0) {
          psys_mat_hair_to_global(sim->ob, sim->psmd->mesh_final, part->from, pa, hairmat);
          mul_m4_v3(hairmat, state->co);
          mul_mat3_m4_v3(hairmat, state->vel);

          if (sim->psys->effectors && (part->flag & PART_CHILD_GUIDE) == 0) {
            do_guides(
                sim->depsgraph, sim->psys->part, sim->psys->effectors, state, p, state->time);
            /* TODO: proper velocity handling */
          }

          if (psys->lattice_deform_data && edit == 0) {
            BKE_lattice_deform_data_eval_co(
                psys->lattice_deform_data, state->co, psys->lattice_strength);
          }
        }
      }
    }
  }
  else if (totchild) {
    // invert_m4_m4(imat, ob->object_to_world().ptr());

    /* interpolate childcache directly if it exists */
    if (psys->childcache) {
      ParticleCacheKey result;
      interpolate_pathcache(psys->childcache[p - totpart], t, &result);
      copy_v3_v3(state->co, result.co);
      copy_v3_v3(state->vel, result.vel);
      copy_qt_qt(state->rot, result.rot);
    }
    else {
      float par_co[3], par_orco[3];

      cpa = psys->child + p - totpart;

      if (state->time < 0.0f) {
        t = psys_get_child_time(psys, cpa, -state->time, nullptr, nullptr);
      }

      if (part->childtype == PART_CHILD_FACES) {
        /* part->parents could still be 0 so we can't test with totparent */
        between = 1;
      }
      if (between) {
        int w = 0;
        float foffset;

        /* get parent states */
        while (w < 4 && cpa->pa[w] >= 0) {
          keys[w].time = state->time;
          psys_get_particle_on_path(sim, cpa->pa[w], keys + w, true);
          w++;
        }

        /* get the original coordinates (orco) for texture usage */
        cpa_num = cpa->num;

        foffset = cpa->foffset;
        cpa_fuv = cpa->fuv;
        cpa_from = PART_FROM_FACE;

        psys_particle_on_emitter(psmd,
                                 cpa_from,
                                 cpa_num,
                                 DMCACHE_ISCHILD,
                                 cpa->fuv,
                                 foffset,
                                 co,
                                 nullptr,
                                 nullptr,
                                 nullptr,
                                 orco);

        /* We need to save the actual root position of the child for
         * positioning it accurately to the surface of the emitter. */
        // copy_v3_v3(cpa_1st, co);

        // mul_m4_v3(ob->object_to_world().ptr(), cpa_1st);

        pa = psys->particles + cpa->parent;

        psys_particle_on_emitter(psmd,
                                 part->from,
                                 pa->num,
                                 pa->num_dmcache,
                                 pa->fuv,
                                 pa->foffset,
                                 par_co,
                                 nullptr,
                                 nullptr,
                                 nullptr,
                                 par_orco);
        if (part->type == PART_HAIR) {
          psys_mat_hair_to_global(sim->ob, sim->psmd->mesh_final, psys->part->from, pa, hairmat);
        }
        else {
          unit_m4(hairmat);
        }

        pa = nullptr;
      }
      else {
        /* get the parent state */
        keys->time = state->time;
        psys_get_particle_on_path(sim, cpa->parent, keys, true);

        /* get the original coordinates (orco) for texture usage */
        pa = psys->particles + cpa->parent;

        cpa_from = part->from;
        cpa_num = pa->num;
        cpa_fuv = pa->fuv;

        psys_particle_on_emitter(psmd,
                                 part->from,
                                 pa->num,
                                 pa->num_dmcache,
                                 pa->fuv,
                                 pa->foffset,
                                 par_co,
                                 nullptr,
                                 nullptr,
                                 nullptr,
                                 par_orco);
        if (part->type == PART_HAIR) {
          psys_particle_on_emitter(psmd,
                                   cpa_from,
                                   cpa_num,
                                   DMCACHE_ISCHILD,
                                   cpa_fuv,
                                   pa->foffset,
                                   co,
                                   nullptr,
                                   nullptr,
                                   nullptr,
                                   orco);
          psys_mat_hair_to_global(sim->ob, sim->psmd->mesh_final, psys->part->from, pa, hairmat);
        }
        else {
          copy_v3_v3(orco, cpa->fuv);
          unit_m4(hairmat);
        }
      }

      /* get different child parameters from textures & vgroups */
      memset(&ctx, 0, sizeof(ParticleThreadContext));
      ctx.sim = *sim;
      ctx.mesh = psmd->mesh_final;
      ctx.ma = ma;
      /* TODO: assign vertex groups */
      get_child_modifier_parameters(part, &ctx, cpa, cpa_from, cpa_num, cpa_fuv, orco, &ptex);

      if (between) {
        int w = 0;

        state->co[0] = state->co[1] = state->co[2] = 0.0f;
        state->vel[0] = state->vel[1] = state->vel[2] = 0.0f;

        /* child position is the weighted sum of parent positions */
        while (w < 4 && cpa->pa[w] >= 0) {
          state->co[0] += cpa->w[w] * keys[w].co[0];
          state->co[1] += cpa->w[w] * keys[w].co[1];
          state->co[2] += cpa->w[w] * keys[w].co[2];

          state->vel[0] += cpa->w[w] * keys[w].vel[0];
          state->vel[1] += cpa->w[w] * keys[w].vel[1];
          state->vel[2] += cpa->w[w] * keys[w].vel[2];
          w++;
        }
        /* apply offset for correct positioning */
        // add_v3_v3(state->co, cpa_1st);
      }
      else {
        /* offset the child from the parent position */
        offset_child(cpa, keys, keys->rot, state, part->childflat, part->childrad);
      }

      par = keys;

      if (vel) {
        copy_particle_key(&tstate, state, 1);
      }

      /* apply different deformations to the child path */
      ParticleChildModifierContext modifier_ctx = {nullptr};
      modifier_ctx.thread_ctx = nullptr;
      modifier_ctx.sim = sim;
      modifier_ctx.ptex = &ptex;
      modifier_ctx.cpa = cpa;
      modifier_ctx.orco = orco;
      modifier_ctx.par_co = par->co;
      modifier_ctx.par_vel = par->vel;
      modifier_ctx.par_rot = par->rot;
      modifier_ctx.par_orco = par_orco;
      modifier_ctx.parent_keys = psys->childcache ? psys->childcache[p - totpart] : nullptr;
      do_child_modifiers(&modifier_ctx, hairmat, state, t);

      /* try to estimate correct velocity */
      if (vel) {
        ParticleKey tstate_tmp;
        float length = len_v3(state->vel);

        if (t >= 0.001f) {
          tstate_tmp.time = t - 0.001f;
          psys_get_particle_on_path(sim, p, &tstate_tmp, false);
          sub_v3_v3v3(state->vel, state->co, tstate_tmp.co);
          normalize_v3(state->vel);
        }
        else {
          tstate_tmp.time = t + 0.001f;
          psys_get_particle_on_path(sim, p, &tstate_tmp, false);
          sub_v3_v3v3(state->vel, tstate_tmp.co, state->co);
          normalize_v3(state->vel);
        }

        mul_v3_fl(state->vel, length);
      }
    }
  }
}

bool psys_get_particle_state(ParticleSimulationData *sim,
                             int p,
                             ParticleKey *state,
                             const bool always)
{
  ParticleSystem *psys = sim->psys;
  ParticleSettings *part = psys->part;
  ParticleData *pa = nullptr;
  ChildParticle *cpa = nullptr;
  float cfra;
  int totpart = psys->totpart;
  float timestep = psys_get_timestep(sim);

  /* negative time means "use current time" */
  cfra = state->time > 0 ? state->time : DEG_get_ctime(sim->depsgraph);

  if (p >= totpart) {
    if (!psys->totchild) {
      return false;
    }

    if (part->childtype == PART_CHILD_FACES) {
      if (!(psys->flag & PSYS_KEYED)) {
        return false;
      }

      cpa = psys->child + p - totpart;

      state->time = psys_get_child_time(psys, cpa, cfra, nullptr, nullptr);

      if (!always) {
        if ((state->time < 0.0f && !(part->flag & PART_UNBORN)) ||
            (state->time > 1.0f && !(part->flag & PART_DIED)))
        {
          return false;
        }
      }

      state->time = (cfra - (part->sta + (part->end - part->sta) * psys_frand(psys, p + 23))) /
                    (part->lifetime * psys_frand(psys, p + 24));

      psys_get_particle_on_path(sim, p, state, true);
      return true;
    }

    cpa = sim->psys->child + p - totpart;
    pa = sim->psys->particles + cpa->parent;
  }
  else {
    pa = sim->psys->particles + p;
  }

  if (pa) {
    if (!always) {
      if ((cfra < pa->time && (part->flag & PART_UNBORN) == 0) ||
          (cfra >= pa->dietime && (part->flag & PART_DIED) == 0))
      {
        return false;
      }
    }

    cfra = std::min(cfra, pa->dietime);
  }

  if (sim->psys->flag & PSYS_KEYED) {
    state->time = -cfra;
    psys_get_particle_on_path(sim, p, state, true);
    return true;
  }

  if (cpa) {
    float mat[4][4];
    ParticleKey *key1;
    float t = (cfra - pa->time) / pa->lifetime;
    const float par_orco[3] = {0.0f, 0.0f, 0.0f};

    key1 = &pa->state;
    offset_child(cpa, key1, key1->rot, state, part->childflat, part->childrad);

    CLAMP(t, 0.0f, 1.0f);

    unit_m4(mat);
    ParticleChildModifierContext modifier_ctx = {nullptr};
    modifier_ctx.thread_ctx = nullptr;
    modifier_ctx.sim = sim;
    modifier_ctx.ptex = nullptr;
    modifier_ctx.cpa = cpa;
    modifier_ctx.orco = cpa->fuv;
    modifier_ctx.par_co = key1->co;
    modifier_ctx.par_vel = key1->vel;
    modifier_ctx.par_rot = key1->rot;
    modifier_ctx.par_orco = par_orco;
    modifier_ctx.parent_keys = psys->childcache ? psys->childcache[p - totpart] : nullptr;

    do_child_modifiers(&modifier_ctx, mat, state, t);

    if (psys->lattice_deform_data) {
      BKE_lattice_deform_data_eval_co(
          psys->lattice_deform_data, state->co, psys->lattice_strength);
    }
  }
  else {
    if (pa->state.time == cfra || ELEM(part->phystype, PART_PHYS_NO, PART_PHYS_KEYED)) {
      copy_particle_key(state, &pa->state, 1);
    }
    else if (pa->prev_state.time == cfra) {
      copy_particle_key(state, &pa->prev_state, 1);
    }
    else {
      float dfra, frs_sec = sim->scene->r.frs_sec;
      /* let's interpolate to try to be as accurate as possible */
      if (pa->state.time + 2.0f >= state->time && pa->prev_state.time - 2.0f <= state->time) {
        if (pa->prev_state.time >= pa->state.time || pa->prev_state.time < 0.0f) {
          /* prev_state is wrong so let's not use it,
           * this can happen at frames 1, 0 or particle birth. */
          dfra = state->time - pa->state.time;

          copy_particle_key(state, &pa->state, 1);

          madd_v3_v3v3fl(state->co, state->co, state->vel, dfra / frs_sec);
        }
        else {
          ParticleKey keys[4];
          float keytime;

          copy_particle_key(keys + 1, &pa->prev_state, 1);
          copy_particle_key(keys + 2, &pa->state, 1);

          dfra = keys[2].time - keys[1].time;

          keytime = (state->time - keys[1].time) / dfra;

          /* convert velocity to timestep size */
          mul_v3_fl(keys[1].vel, dfra * timestep);
          mul_v3_fl(keys[2].vel, dfra * timestep);

          psys_interpolate_particle(-1, keys, keytime, state, true);

          /* convert back to real velocity */
          mul_v3_fl(state->vel, 1.0f / (dfra * timestep));

          interp_v3_v3v3(state->ave, keys[1].ave, keys[2].ave, keytime);
          interp_qt_qtqt(state->rot, keys[1].rot, keys[2].rot, keytime);
        }
      }
      else if (pa->state.time + 1.0f >= state->time && pa->state.time - 1.0f <= state->time) {
        /* linear interpolation using only pa->state */

        dfra = state->time - pa->state.time;

        copy_particle_key(state, &pa->state, 1);

        madd_v3_v3v3fl(state->co, state->co, state->vel, dfra / frs_sec);
      }
      else {
        /* Extrapolating over big ranges is not accurate
         * so let's just give something close to reasonable back. */
        copy_particle_key(state, &pa->state, 0);
      }
    }

    if (sim->psys->lattice_deform_data) {
      BKE_lattice_deform_data_eval_co(
          sim->psys->lattice_deform_data, state->co, psys->lattice_strength);
    }
  }

  return true;
}

void psys_get_dupli_texture(ParticleSystem *psys,
                            ParticleSettings *part,
                            ParticleSystemModifierData *psmd,
                            ParticleData *pa,
                            ChildParticle *cpa,
                            float uv[2],
                            float orco[3])
{
  float loc[3];
  int num;

  /* XXX: on checking '(psmd->dm != nullptr)'
   * This is incorrect but needed for meta-ball evaluation.
   * Ideally this would be calculated via the depsgraph, however with meta-balls,
   * the entire scenes dupli's are scanned, which also looks into uncalculated data.
   *
   * For now just include this workaround as an alternative to crashing,
   * but longer term meta-balls should behave in a more manageable way, see: #46622. */

  uv[0] = uv[1] = 0.0f;

  /* Grid distribution doesn't support UV or emit from vertex mode */
  bool is_grid = (part->distr == PART_DISTR_GRID && part->from != PART_FROM_VERT);

  if (cpa) {
    if ((part->childtype == PART_CHILD_FACES) && (psmd->mesh_final != nullptr)) {
      if (!is_grid) {
        CustomData *mtf_data = &psmd->mesh_final->fdata_legacy;
        const int uv_idx = CustomData_get_render_layer(mtf_data, CD_MTFACE);

        if (uv_idx >= 0) {
          const MTFace *mtface = static_cast<const MTFace *>(
              CustomData_get_layer_n(mtf_data, CD_MTFACE, uv_idx));
          if (mtface != nullptr) {
            const MFace *mface = static_cast<const MFace *>(
                CustomData_get_for_write(&psmd->mesh_final->fdata_legacy,
                                         cpa->num,
                                         CD_MFACE,
                                         psmd->mesh_final->totface_legacy));
            mtface += cpa->num;
            psys_interpolate_uvs(mtface, mface->v4, cpa->fuv, uv);
          }
        }
      }

      psys_particle_on_emitter(psmd,
                               PART_FROM_FACE,
                               cpa->num,
                               DMCACHE_ISCHILD,
                               cpa->fuv,
                               cpa->foffset,
                               loc,
                               nullptr,
                               nullptr,
                               nullptr,
                               orco);
      return;
    }

    pa = psys->particles + cpa->pa[0];
  }

  if ((part->from == PART_FROM_FACE) && (psmd->mesh_final != nullptr) && !is_grid) {
    num = pa->num_dmcache;

    if (num == DMCACHE_NOTFOUND) {
      num = pa->num;
    }

    if (num >= psmd->mesh_final->totface_legacy) {
      /* happens when simplify is enabled
       * gives invalid coords but would crash otherwise */
      num = DMCACHE_NOTFOUND;
    }

    if (!ELEM(num, DMCACHE_NOTFOUND, DMCACHE_ISCHILD)) {
      CustomData *mtf_data = &psmd->mesh_final->fdata_legacy;
      const int uv_idx = CustomData_get_render_layer(mtf_data, CD_MTFACE);

      if (uv_idx >= 0) {
        const MTFace *mtface = static_cast<const MTFace *>(
            CustomData_get_layer_n(mtf_data, CD_MTFACE, uv_idx));
        const MFace *mface = static_cast<const MFace *>(CustomData_get_for_write(
            &psmd->mesh_final->fdata_legacy, num, CD_MFACE, psmd->mesh_final->totface_legacy));
        mtface += num;
        psys_interpolate_uvs(mtface, mface->v4, pa->fuv, uv);
      }
    }
  }

  psys_particle_on_emitter(psmd,
                           part->from,
                           pa->num,
                           pa->num_dmcache,
                           pa->fuv,
                           pa->foffset,
                           loc,
                           nullptr,
                           nullptr,
                           nullptr,
                           orco);
}

void psys_get_dupli_path_transform(ParticleSimulationData *sim,
                                   ParticleData *pa,
                                   ChildParticle *cpa,
                                   ParticleCacheKey *cache,
                                   float mat[4][4],
                                   float *scale)
{
  Object *ob = sim->ob;
  ParticleSystem *psys = sim->psys;
  ParticleSystemModifierData *psmd = sim->psmd;
  float loc[3], nor[3], vec[3], side[3], len;
  float xvec[3] = {-1.0, 0.0, 0.0}, nmat[3][3];

  sub_v3_v3v3(vec, (cache + cache->segments)->co, cache->co);
  len = normalize_v3(vec);

  if (pa == nullptr) {
    pa = psys->particles + cpa->pa[0];
  }

  psys_particle_on_emitter(psmd,
                           sim->psys->part->from,
                           pa->num,
                           pa->num_dmcache,
                           pa->fuv,
                           pa->foffset,
                           loc,
                           nor,
                           nullptr,
                           nullptr,
                           nullptr);

  if (psys->part->rotmode == PART_ROT_VEL) {
    transpose_m3_m4(nmat, ob->world_to_object().ptr());
    mul_m3_v3(nmat, nor);
    normalize_v3(nor);

    /* make sure that we get a proper side vector */
    if (fabsf(dot_v3v3(nor, vec)) > 0.999999f) {
      if (fabsf(dot_v3v3(nor, xvec)) > 0.999999f) {
        nor[0] = 0.0f;
        nor[1] = 1.0f;
        nor[2] = 0.0f;
      }
      else {
        nor[0] = 1.0f;
        nor[1] = 0.0f;
        nor[2] = 0.0f;
      }
    }
    cross_v3_v3v3(side, nor, vec);
    normalize_v3(side);

    /* rotate side vector around vec */
    if (psys->part->phasefac != 0) {
      float q_phase[4];
      float phasefac = psys->part->phasefac;
      if (psys->part->randphasefac != 0.0f) {
        phasefac += psys->part->randphasefac * psys_frand(psys, (pa - psys->particles) + 20);
      }
      axis_angle_to_quat(q_phase, vec, phasefac * float(M_PI));

      mul_qt_v3(q_phase, side);
    }

    cross_v3_v3v3(nor, vec, side);

    unit_m4(mat);
    copy_v3_v3(mat[0], vec);
    copy_v3_v3(mat[1], side);
    copy_v3_v3(mat[2], nor);
  }
  else {
    quat_to_mat4(mat, pa->state.rot);
  }

  *scale = len;
}

void psys_apply_hair_lattice(Depsgraph *depsgraph, Scene *scene, Object *ob, ParticleSystem *psys)
{
  ParticleSimulationData sim = {nullptr};
  sim.depsgraph = depsgraph;
  sim.scene = scene;
  sim.ob = ob;
  sim.psys = psys;
  sim.psmd = psys_get_modifier(ob, psys);

  psys_sim_data_init(&sim);

  if (psys->lattice_deform_data) {
    ParticleData *pa = psys->particles;
    HairKey *hkey;
    int p, h;
    float hairmat[4][4], imat[4][4];

    for (p = 0; p < psys->totpart; p++, pa++) {
      psys_mat_hair_to_global(sim.ob, sim.psmd->mesh_final, psys->part->from, pa, hairmat);
      invert_m4_m4(imat, hairmat);

      hkey = pa->hair;
      for (h = 0; h < pa->totkey; h++, hkey++) {
        mul_m4_v3(hairmat, hkey->co);
        BKE_lattice_deform_data_eval_co(
            psys->lattice_deform_data, hkey->co, psys->lattice_strength);
        mul_m4_v3(imat, hkey->co);
      }
    }

    /* protect the applied shape */
    psys->flag |= PSYS_EDITED;
  }

  psys_sim_data_free(&sim);
}

void BKE_particle_co_hair(const ParticleSystem *particlesystem,
                          const Object *object,
                          int particle_no,
                          int step,
                          float n_co[3])
{
  ParticleSettings *part = nullptr;
  ParticleData *pars = nullptr;
  ParticleCacheKey *cache = nullptr;
  int totchild = 0;
  int totpart;
  int max_k = 0;

  if (particlesystem == nullptr) {
    return;
  }

  part = particlesystem->part;
  pars = particlesystem->particles;
  totpart = particlesystem->totcached;
  totchild = particlesystem->totchildcache;

  if (part == nullptr || pars == nullptr) {
    return;
  }

  if (ELEM(part->ren_as, PART_DRAW_OB, PART_DRAW_GR, PART_DRAW_NOT)) {
    return;
  }

  /* can happen for disconnected/global hair */
  if (part->type == PART_HAIR && !particlesystem->childcache) {
    totchild = 0;
  }

  if (particle_no < totpart && particlesystem->pathcache) {
    cache = particlesystem->pathcache[particle_no];
    max_k = int(cache->segments);
  }
  else if (particle_no < totpart + totchild && particlesystem->childcache) {
    cache = particlesystem->childcache[particle_no - totpart];

    if (cache->segments < 0) {
      max_k = 0;
    }
    else {
      max_k = int(cache->segments);
    }
  }
  else {
    return;
  }

  /* Strands key loop data stored in cache + step->co. */
  if (step >= 0 && step <= max_k) {
    copy_v3_v3(n_co, (cache + step)->co);
    mul_m4_v3(particlesystem->imat, n_co);
    mul_m4_v3(object->object_to_world().ptr(), n_co);
  }
}

/* return < 0 means invalid (no matching tessellated face could be found). */
static int tessfaceidx_on_emitter(ParticleSystem *particlesystem,
                                  ParticleSystemModifierData *modifier,
                                  ParticleData *particle,
                                  int particle_no,
                                  float (**r_fuv)[4])
{
  ParticleSettings *part = nullptr;
  int totpart;
  int totchild = 0;
  int totface;
  int totvert;
  int num = -1;

  BKE_mesh_tessface_ensure(modifier->mesh_final); /* BMESH - UNTIL MODIFIER IS UPDATED FOR POLYS */
  totface = modifier->mesh_final->totface_legacy;
  totvert = modifier->mesh_final->verts_num;

  /* 1. check that everything is ok & updated */
  if (!particlesystem || !totface) {
    return num;
  }

  part = particlesystem->part;
  /* NOTE: only hair, keyed and baked particles may have cached items... */
  totpart = particlesystem->totcached != 0 ? particlesystem->totcached : particlesystem->totpart;
  totchild = particlesystem->totchildcache != 0 ? particlesystem->totchildcache :
                                                  particlesystem->totchild;

  /* can happen for disconnected/global hair */
  if (part->type == PART_HAIR && !particlesystem->childcache) {
    totchild = 0;
  }

  if (particle_no >= totpart + totchild) {
    return num;
  }

  /* 2. get matching face index. */
  if (particle_no < totpart) {
    num = (ELEM(particle->num_dmcache, DMCACHE_ISCHILD, DMCACHE_NOTFOUND)) ? particle->num :
                                                                             particle->num_dmcache;

    if (ELEM(part->from, PART_FROM_FACE, PART_FROM_VOLUME)) {
      if (num != DMCACHE_NOTFOUND && num < totface) {
        *r_fuv = &particle->fuv;
        return num;
      }
    }
    else if (part->from == PART_FROM_VERT) {
      if (num != DMCACHE_NOTFOUND && num < totvert) {
        const MFace *mface = static_cast<const MFace *>(
            CustomData_get_layer(&modifier->mesh_final->fdata_legacy, CD_MFACE));

        *r_fuv = &particle->fuv;

        /* This finds the first face to contain the emitting vertex,
         * this is not ideal, but is mostly fine as UV seams generally
         * map to equal-colored parts of a texture */
        for (int i = 0; i < totface; i++, mface++) {
          if (ELEM(num, mface->v1, mface->v2, mface->v3, mface->v4)) {
            return i;
          }
        }
      }
    }
  }
  else {
    ChildParticle *cpa = particlesystem->child + particle_no - totpart;
    num = cpa->num;

    if (part->childtype == PART_CHILD_FACES) {
      if (ELEM(part->from, PART_FROM_FACE, PART_FROM_VOLUME, PART_FROM_VERT)) {
        if (num != DMCACHE_NOTFOUND && num < totface) {
          *r_fuv = &cpa->fuv;
          return num;
        }
      }
    }
    else {
      ParticleData *parent = particlesystem->particles + cpa->parent;
      num = parent->num_dmcache;

      if (num == DMCACHE_NOTFOUND) {
        num = parent->num;
      }

      if (ELEM(part->from, PART_FROM_FACE, PART_FROM_VOLUME)) {
        if (num != DMCACHE_NOTFOUND && num < totface) {
          *r_fuv = &parent->fuv;
          return num;
        }
      }
      else if (part->from == PART_FROM_VERT) {
        if (num != DMCACHE_NOTFOUND && num < totvert) {
          const MFace *mface = static_cast<const MFace *>(
              CustomData_get_layer(&modifier->mesh_final->fdata_legacy, CD_MFACE));

          *r_fuv = &parent->fuv;

          /* This finds the first face to contain the emitting vertex,
           * this is not ideal, but is mostly fine as UV seams generally
           * map to equal-colored parts of a texture */
          for (int i = 0; i < totface; i++, mface++) {
            if (ELEM(num, mface->v1, mface->v2, mface->v3, mface->v4)) {
              return i;
            }
          }
        }
      }
    }
  }

  return -1;
}

void BKE_particle_uv_on_emitter(ParticleSystem *particlesystem,
                                ReportList *reports,
                                ParticleSystemModifierData *modifier,
                                ParticleData *particle,
                                int particle_no,
                                int uv_no,
                                float r_uv[2])
{
  if (modifier->mesh_final == nullptr) {
    BKE_report(reports, RPT_ERROR, "Object was not yet evaluated");
    zero_v2(r_uv);
    return;
  }
  if (modifier->mesh_final->uv_map_names().is_empty()) {
    BKE_report(reports, RPT_ERROR, "Mesh has no UV data");
    zero_v2(r_uv);
    return;
  }

  {
    float (*fuv)[4];
    /* Note all sanity checks are done in this helper func. */
    const int num = tessfaceidx_on_emitter(particlesystem, modifier, particle, particle_no, &fuv);

    if (num < 0) {
      /* No matching face found. */
      zero_v2(r_uv);
    }
    else {
      const MFace *mfaces = static_cast<const MFace *>(
          CustomData_get_layer(&modifier->mesh_final->fdata_legacy, CD_MFACE));
      const MFace *mface = &mfaces[num];
      const MTFace *mtface = static_cast<const MTFace *>(
          CustomData_get_layer_n(&modifier->mesh_final->fdata_legacy, CD_MTFACE, uv_no));

      psys_interpolate_uvs(&mtface[num], mface->v4, *fuv, r_uv);
    }
  }
}

void BKE_particle_mcol_on_emitter(ParticleSystem *particlesystem,
                                  ReportList *reports,
                                  ParticleSystemModifierData *modifier,
                                  ParticleData *particle,
                                  int particle_no,
                                  int vcol_no,
                                  float r_mcol[3])
{
  if (!CustomData_has_layer(&modifier->mesh_final->fdata_legacy, CD_MCOL)) {
    BKE_report(reports, RPT_ERROR, "Mesh has no VCol data");
    zero_v3(r_mcol);
    return;
  }

  {
    float (*fuv)[4];
    /* Note all sanity checks are done in this helper func. */
    const int num = tessfaceidx_on_emitter(particlesystem, modifier, particle, particle_no, &fuv);

    if (num < 0) {
      /* No matching face found. */
      zero_v3(r_mcol);
    }
    else {
      const MFace *mfaces = static_cast<const MFace *>(
          CustomData_get_layer(&modifier->mesh_final->fdata_legacy, CD_MFACE));
      const MFace *mface = &mfaces[num];
      const MCol *mc = static_cast<const MCol *>(
          CustomData_get_layer_n(&modifier->mesh_final->fdata_legacy, CD_MCOL, vcol_no));
      MCol mcol;

      psys_interpolate_mcol(&mc[num * 4], mface->v4, *fuv, &mcol);
      r_mcol[0] = float(mcol.b) / 255.0f;
      r_mcol[1] = float(mcol.g) / 255.0f;
      r_mcol[2] = float(mcol.r) / 255.0f;
    }
  }
}

/* Draw Engine */

void (*BKE_particle_batch_cache_dirty_tag_cb)(ParticleSystem *psys, int mode) = nullptr;
void (*BKE_particle_batch_cache_free_cb)(ParticleSystem *psys) = nullptr;

void BKE_particle_batch_cache_dirty_tag(ParticleSystem *psys, int mode)
{
  if (psys->batch_cache) {
    BKE_particle_batch_cache_dirty_tag_cb(psys, mode);
  }
}
void BKE_particle_batch_cache_free(ParticleSystem *psys)
{
  if (psys->batch_cache) {
    BKE_particle_batch_cache_free_cb(psys);
  }
}

void BKE_particle_system_blend_write(BlendWriter *writer, ListBaseT<ParticleSystem> *particles)
{
  for (ParticleSystem &psys : *particles) {
    writer->write_struct(&psys);

    if (psys.particles) {
      writer->write_struct_array(psys.totpart, psys.particles);

      if (psys.particles->hair) {
        ParticleData *pa = psys.particles;

        for (int a = 0; a < psys.totpart; a++, pa++) {
          writer->write_struct_array(pa->totkey, pa->hair);
        }
      }

      if (psys.particles->boid && (psys.part->phystype == PART_PHYS_BOIDS)) {
        writer->write_struct_array(psys.totpart, psys.particles->boid);
      }

      if (psys.part->fluid && (psys.part->phystype == PART_PHYS_FLUID) &&
          (psys.part->fluid->flag & SPH_VISCOELASTIC_SPRINGS))
      {
        writer->write_struct_array(psys.tot_fluidsprings, psys.fluid_springs);
      }
    }
    for (ParticleTarget &pt : psys.targets) {
      writer->write_struct(&pt);
    }

    if (psys.child) {
      writer->write_struct_array(psys.totchild, psys.child);
    }

    if (psys.clmd) {
      writer->write_struct(psys.clmd);
      writer->write_struct(psys.clmd->sim_parms);
      writer->write_struct(psys.clmd->coll_parms);
    }

    BKE_ptcache_blend_write(writer, &psys.ptcaches);
  }
}

void BKE_particle_system_blend_read_data(BlendDataReader *reader,
                                         ListBaseT<ParticleSystem> *particles)
{
  ParticleData *pa;
  int a;

  for (ParticleSystem &psys : *particles) {
    BLO_read_array_and_validate_size(reader, &psys.particles, &psys.totpart);

    if (psys.particles && psys.particles->hair) {
      for (a = 0, pa = psys.particles; a < psys.totpart; a++, pa++) {
        BLO_read_array_and_validate_size(reader, &pa->hair, &pa->totkey);
      }
    }

    if (psys.particles && psys.particles->keys) {
      for (a = 0, pa = psys.particles; a < psys.totpart; a++, pa++) {
        pa->keys = nullptr;
        pa->totkey = 0;
      }

      psys.flag &= ~PSYS_KEYED;
    }

    if (psys.particles && psys.particles->boid) {
      pa = psys.particles;
      BLO_read_array_and_validate_size(reader, &pa->boid, &psys.totpart);

      if (pa->boid) {
        /* This is purely runtime data, but still can be an issue if left dangling. */
        pa->boid->ground = nullptr;

        for (a = 1, pa++; a < psys.totpart; a++, pa++) {
          pa->boid = (pa - 1)->boid + 1;
          pa->boid->ground = nullptr;
        }
      }
    }
    else if (psys.particles) {
      for (a = 0, pa = psys.particles; a < psys.totpart; a++, pa++) {
        pa->boid = nullptr;
      }
    }

    BLO_read_array_and_validate_size(reader, &psys.fluid_springs, &psys.tot_fluidsprings);

    BLO_read_array_and_validate_size(reader, &psys.child, &psys.totchild);
    psys.effectors = nullptr;

    BLO_read_struct_list(reader, ParticleTarget, &psys.targets);

    psys.edit = nullptr;
    psys.free_edit = nullptr;
    psys.pathcache = nullptr;
    psys.childcache = nullptr;
    psys.pathcachebufs.clear_no_delete();
    psys.childcachebufs.clear_no_delete();
    psys.pdd = nullptr;

    if (psys.clmd) {
      BLO_read_struct(reader, ClothModifierData, &psys.clmd);
      psys.clmd->clothObject = nullptr;
      psys.clmd->hairdata = nullptr;

      BLO_read_struct(reader, ClothSimSettings, &psys.clmd->sim_parms);
      BLO_read_struct(reader, ClothCollSettings, &psys.clmd->coll_parms);

      if (psys.clmd->sim_parms) {
        psys.clmd->sim_parms->effector_weights = nullptr;
        if (psys.clmd->sim_parms->presets > 10) {
          psys.clmd->sim_parms->presets = 0;
        }
      }

      psys.hair_in_mesh = psys.hair_out_mesh = nullptr;
      psys.clmd->solver_result = nullptr;
    }

    BKE_ptcache_blend_read_data(reader, &psys.ptcaches, &psys.pointcache, 0);
    if (psys.clmd) {
      psys.clmd->point_cache = psys.pointcache;
    }

    psys.tree = nullptr;
    psys.bvhtree = nullptr;

    psys.orig_psys = nullptr;
    psys.batch_cache = nullptr;
  }
}

void BKE_particle_system_blend_read_after_liblink(BlendLibReader * /*reader*/,
                                                  Object *ob,
                                                  ID * /*id*/,
                                                  ListBaseT<ParticleSystem> *particles)
{
  for (ParticleSystem &psys : particles->items_mutable()) {
    if (psys.part) {
      if (psys.clmd) {
        /* XXX(@ideasman42): from reading existing code this seems correct but intended usage
         * of point-cache with cloth should be added in #ParticleSystem. */
        psys.clmd->point_cache = psys.pointcache;
        psys.clmd->ptcaches.first = psys.clmd->ptcaches.last = nullptr;
        psys.clmd->modifier.error = nullptr;
      }
    }
    else {
      /* Particle modifier must be removed before particle system. */
      ParticleSystemModifierData *psmd = psys_get_modifier(ob, &psys);
      BKE_modifier_remove_from_list(ob, reinterpret_cast<ModifierData *>(psmd));
      BKE_modifier_free(reinterpret_cast<ModifierData *>(psmd));

      BLI_remlink(particles, &psys);
      MEM_delete(&psys);
    }
  }
}

/** \} */

}  // namespace blender