Add Chromium-only Blender WebEngine parity work

blender-5.2.0/intern/cycles/kernel/util/ies.h

@@ -0,0 +1,145 @@
+/* SPDX-FileCopyrightText: 2011-2022 Blender Foundation
+ *
+ * SPDX-License-Identifier: Apache-2.0 */
+
+#pragma once
+
+#include "kernel/globals.h"
+
+CCL_NAMESPACE_BEGIN
+
+/* IES Light */
+
+ccl_device_inline float interpolate_ies_vertical(KernelGlobals kg,
+                                                 const int ofs,
+                                                 const bool wrap_vlow,
+                                                 const bool wrap_vhigh,
+                                                 const int v,
+                                                 const int v_num,
+                                                 const float v_frac,
+                                                 const int h)
+{
+  /* Since lookups are performed in spherical coordinates, clamping the coordinates at the low end
+   * of v (corresponding to the north pole) would result in artifacts. The proper way of dealing
+   * with this would be to lookup the corresponding value on the other side of the pole, but since
+   * the horizontal coordinates might be nonuniform, this would require yet another interpolation.
+   * Therefore, the assumption is made that the light is going to be symmetrical, which means that
+   * we can just take the corresponding value at the current horizontal coordinate. */
+
+#define IES_LOOKUP(v) kernel_data_fetch(ies, ofs + h * v_num + (v))
+
+  /* Look up the inner two points directly. */
+  const float c = IES_LOOKUP(v + 1);
+  const float b = IES_LOOKUP(v);
+
+  /* Look up first point, or fall back to second point if not available. */
+  float a = b;
+  if (v > 0) {
+    a = IES_LOOKUP(v - 1);
+  }
+  else if (wrap_vlow) {
+    a = IES_LOOKUP(1);
+  }
+
+  /* Look up last point, or fall back to third point if not available. */
+  float d = c;
+  if (v + 2 < v_num) {
+    d = IES_LOOKUP(v + 2);
+  }
+  else if (wrap_vhigh) {
+    d = IES_LOOKUP(v_num - 2);
+  }
+
+#undef IES_LOOKUP
+
+  return cubic_interp(a, b, c, d, v_frac);
+}
+
+ccl_device_inline float kernel_ies_interp(KernelGlobals kg,
+                                          const int slot,
+                                          const float h_angle,
+                                          const float v_angle)
+{
+  /* Find offset of the IES data in the table. */
+  int ofs = __float_as_int(kernel_data_fetch(ies, slot));
+  if (ofs == -1) {
+    return 100.0f;
+  }
+
+  const int h_num = __float_as_int(kernel_data_fetch(ies, ofs++));
+  const int v_num = __float_as_int(kernel_data_fetch(ies, ofs++));
+
+#define IES_LOOKUP_ANGLE_H(h) kernel_data_fetch(ies, ofs + (h))
+#define IES_LOOKUP_ANGLE_V(v) kernel_data_fetch(ies, ofs + h_num + (v))
+
+  /* Check whether the angle is within the bounds of the IES texture. */
+  const float v_low = IES_LOOKUP_ANGLE_V(0);
+  const float v_high = IES_LOOKUP_ANGLE_V(v_num - 1);
+  const float h_low = IES_LOOKUP_ANGLE_H(0);
+  const float h_high = IES_LOOKUP_ANGLE_H(h_num - 1);
+  if (v_angle < v_low || v_angle >= v_high) {
+    return 0.0f;
+  }
+  if (h_angle < h_low || h_angle >= h_high) {
+    return 0.0f;
+  }
+
+  /* If the texture covers the full 360° range horizontally, wrap around the lookup
+   * to get proper cubic interpolation. Otherwise, just set the out-of-range values to zero.
+   * Similar logic for V, but there we check the lower and upper wrap separately. */
+  const bool wrap_h = (h_low < 1e-7f && h_high > M_2PI_F - 1e-7f);
+  const bool wrap_vlow = (v_low < 1e-7f);
+  const bool wrap_vhigh = (v_high > M_PI_F - 1e-7f);
+
+  /* Lookup the angles to find the table position. */
+  int h_i;
+  int v_i;
+  /* TODO(lukas): Consider using bisection.
+   * Probably not worth it for the vast majority of IES files. */
+  for (h_i = 0; IES_LOOKUP_ANGLE_H(h_i + 1) < h_angle; h_i++) {
+    ;
+  }
+  for (v_i = 0; IES_LOOKUP_ANGLE_V(v_i + 1) < v_angle; v_i++) {
+    ;
+  }
+
+  const float h_frac = inverse_lerp(IES_LOOKUP_ANGLE_H(h_i), IES_LOOKUP_ANGLE_H(h_i + 1), h_angle);
+  const float v_frac = inverse_lerp(IES_LOOKUP_ANGLE_V(v_i), IES_LOOKUP_ANGLE_V(v_i + 1), v_angle);
+
+#undef IES_LOOKUP_ANGLE_H
+#undef IES_LOOKUP_ANGLE_V
+
+  /* Skip forward to the actual intensity data. */
+  ofs += h_num + v_num;
+
+  /* Interpolate the inner two points directly. */
+  const float b = interpolate_ies_vertical(
+      kg, ofs, wrap_vlow, wrap_vhigh, v_i, v_num, v_frac, h_i);
+  const float c = interpolate_ies_vertical(
+      kg, ofs, wrap_vlow, wrap_vhigh, v_i, v_num, v_frac, h_i + 1);
+
+  /* Interpolate first point, or fall back to second point if not available. */
+  float a = b;
+  if (h_i > 0) {
+    a = interpolate_ies_vertical(kg, ofs, wrap_vlow, wrap_vhigh, v_i, v_num, v_frac, h_i - 1);
+  }
+  else if (wrap_h) {
+    /* The last entry (360°) equals the first one, so we need to wrap around to the one before. */
+    a = interpolate_ies_vertical(kg, ofs, wrap_vlow, wrap_vhigh, v_i, v_num, v_frac, h_num - 2);
+  }
+
+  /* Interpolate last point, or fall back to second point if not available. */
+  float d = b;
+  if (h_i + 2 < h_num) {
+    d = interpolate_ies_vertical(kg, ofs, wrap_vlow, wrap_vhigh, v_i, v_num, v_frac, h_i + 2);
+  }
+  else if (wrap_h) {
+    /* Same logic here, wrap around to the second element if necessary. */
+    d = interpolate_ies_vertical(kg, ofs, wrap_vlow, wrap_vhigh, v_i, v_num, v_frac, 1);
+  }
+
+  /* Cubic interpolation can result in negative values, so get rid of them. */
+  return max(cubic_interp(a, b, c, d, h_frac), 0.0f);
+}
+
+CCL_NAMESPACE_END