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/* SPDX-License-Identifier: Apache-2.0
* Copyright 2011-2022 Blender Foundation */
#pragma once
CCL_NAMESPACE_BEGIN
/* IES Light */
ccl_device_inline float interpolate_ies_vertical(
KernelGlobals kg, int ofs, int v, int v_num, float v_frac, 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))
/* If v is zero, assume symmetry and read at v=1 instead of v=-1. */
float a = IES_LOOKUP((v == 0) ? 1 : v - 1);
float b = IES_LOOKUP(v);
float c = IES_LOOKUP(v + 1);
float d = IES_LOOKUP(min(v + 2, v_num - 1));
#undef IES_LOOKUP
return cubic_interp(a, b, c, d, v_frac);
}
ccl_device_inline float kernel_ies_interp(KernelGlobals kg, int slot, float h_angle, 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;
}
int h_num = __float_as_int(kernel_data_fetch(ies, ofs++));
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. */
if (v_angle >= IES_LOOKUP_ANGLE_V(v_num - 1)) {
return 0.0f;
}
kernel_assert(v_angle >= IES_LOOKUP_ANGLE_V(0));
kernel_assert(h_angle >= IES_LOOKUP_ANGLE_H(0));
kernel_assert(h_angle <= IES_LOOKUP_ANGLE_H(h_num - 1));
/* Lookup the angles to find the table position. */
int h_i, 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++)
;
float h_frac = inverse_lerp(IES_LOOKUP_ANGLE_H(h_i), IES_LOOKUP_ANGLE_H(h_i + 1), h_angle);
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;
/* Perform cubic interpolation along the horizontal coordinate to get the intensity value.
* If h_i is zero, just wrap around since the horizontal angles always go over the full circle.
* However, the last entry (360°) equals the first one, so we need to wrap around to the one
* before that. */
float a = interpolate_ies_vertical(
kg, ofs, v_i, v_num, v_frac, (h_i == 0) ? h_num - 2 : h_i - 1);
float b = interpolate_ies_vertical(kg, ofs, v_i, v_num, v_frac, h_i);
float c = interpolate_ies_vertical(kg, ofs, v_i, v_num, v_frac, h_i + 1);
/* Same logic here, wrap around to the second element if necessary. */
float d = interpolate_ies_vertical(
kg, ofs, v_i, v_num, v_frac, (h_i + 2 == h_num) ? 1 : h_i + 2);
/* 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_device_noinline void svm_node_ies(KernelGlobals kg,
ccl_private ShaderData *sd,
ccl_private float *stack,
uint4 node)
{
uint vector_offset, strength_offset, fac_offset, slot = node.z;
svm_unpack_node_uchar3(node.y, &strength_offset, &vector_offset, &fac_offset);
float3 vector = stack_load_float3(stack, vector_offset);
float strength = stack_load_float_default(stack, strength_offset, node.w);
vector = normalize(vector);
float v_angle = safe_acosf(-vector.z);
float h_angle = atan2f(vector.x, vector.y) + M_PI_F;
float fac = strength * kernel_ies_interp(kg, slot, h_angle, v_angle);
if (stack_valid(fac_offset)) {
stack_store_float(stack, fac_offset, fac);
}
}
CCL_NAMESPACE_END
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