/* SPDX-FileCopyrightText: 2011-2022 Blender Foundation
 *
 * SPDX-License-Identifier: Apache-2.0 */

/* Volume Primitive
 *
 * Volumes are just regions inside meshes with the mesh surface as boundaries.
 * There isn't as much data to access as for surfaces, there is only a position
 * to do lookups in 3D voxel or procedural textures.
 *
 * 3D voxel textures can be assigned as attributes per mesh, which means the
 * same shader can be used for volume objects with different densities, etc. */

#pragma once

#include "kernel/globals.h"

#include "kernel/geom/attribute.h"
#include "kernel/geom/object.h"

#include "kernel/util/image_3d.h"

CCL_NAMESPACE_BEGIN

#ifdef __VOLUME__

/* Return position normalized to 0..1 in mesh bounds */

template<typename Float3Type>
ccl_device_inline Float3Type volume_normalized_position(KernelGlobals kg,
                                                        const ccl_private ShaderData *sd,
                                                        Float3Type P)
{
  const AttributeDescriptor desc = find_attribute(kg, sd, ATTR_STD_GENERATED_TRANSFORM);

  object_inverse_position_transform_if_object(kg, sd, &P);

  if (is_attribute_found(desc)) {
    const Transform tfm = primitive_attribute_matrix(kg, desc);
    P = transform_point(&tfm, P);
  }

  return P;
}

template<typename T> ccl_device_inline T volume_attribute_value(const float4 value);

ccl_device_template_spec float volume_attribute_value(const float4 value)
{
  return average(make_float3(value));
}

ccl_device_template_spec float2 volume_attribute_value(const float4 value)
{
  return make_float2(value.x, value.y);
}

ccl_device_template_spec float3 volume_attribute_value(const float4 value)
{
  return make_float3(value);
}

ccl_device_template_spec float4 volume_attribute_value(const float4 value)
{
  return value;
}

ccl_device float volume_attribute_alpha(const float4 value)
{
  return value.w;
}

ccl_device float4 volume_attribute_float4(KernelGlobals kg,
                                          ccl_private ShaderData *sd,
                                          const AttributeDescriptor desc,
                                          const bool stochastic)
{
  if (desc.element & (ATTR_ELEMENT_OBJECT | ATTR_ELEMENT_MESH)) {
    switch (desc.type) {
      case NODE_ATTR_FLOAT: {
        const float f = kernel_data_fetch(attributes_float, desc.offset);
        return make_float4(f, f, f, 1.0f);
      }
      case NODE_ATTR_FLOAT2: {
        const float2 f = kernel_data_fetch(attributes_float2, desc.offset);
        return make_float4(f.x, f.y, 0.0f, 1.0f);
      }
      case NODE_ATTR_FLOAT3: {
        const float3 f = kernel_data_fetch(attributes_float3, desc.offset);
        return make_float4(f.x, f.y, f.z, 1.0f);
      }
      case NODE_ATTR_FLOAT4:
      case NODE_ATTR_RGBA:
        return kernel_data_fetch(attributes_float4, desc.offset);
      case NODE_ATTR_MATRIX:
        return zero_float4();
    }
  }
  if (desc.element & ATTR_ELEMENT_VOXEL) {
    /* todo: optimize this so we don't have to transform both here and in
     * kernel_image_interp_3d when possible. Also could optimize for the
     * common case where transform is translation/scale only. */
    float3 P = sd->P;
    object_inverse_position_transform(kg, sd, &P);
    const InterpolationType interp = (sd->flag & SD_VOLUME_CUBIC) ? INTERPOLATION_CUBIC :
                                                                    INTERPOLATION_NONE;
    const float4 value = kernel_image_interp_3d(kg, sd, desc.offset, P, interp, stochastic);
    if (value.w > 1e-6f && value.w != 1.0f) {
      /* For RGBA colors, unpremultiply after interpolation. */
      return make_float4(make_float3(value) / value.w, value.w);
    }
    return value;
  }
  return zero_float4();
}

#endif

CCL_NAMESPACE_END