61 lines
1.7 KiB
C++
61 lines
1.7 KiB
C++
/* SPDX-FileCopyrightText: 2011-2022 Blender Foundation
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*
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* SPDX-License-Identifier: Apache-2.0 */
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#pragma once
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#include "kernel/globals.h"
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#include "kernel/light/common.h"
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CCL_NAMESPACE_BEGIN
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/* Simple CDF based sampling over all lights in the scene, without taking into
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* account shading position or normal. */
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ccl_device int light_distribution_sample(KernelGlobals kg, const float rand)
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{
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/* This is basically std::upper_bound as used by PBRT, to find a point light or
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* triangle to emit from, proportional to area. a good improvement would be to
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* also sample proportional to power, though it's not so well defined with
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* arbitrary shaders. */
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int first = 0;
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int len = kernel_data.integrator.num_distribution + 1;
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do {
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const int half_len = len >> 1;
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const int middle = first + half_len;
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if (rand < kernel_data_fetch(light_distribution, middle).totarea) {
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len = half_len;
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}
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else {
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first = middle + 1;
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len = len - half_len - 1;
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}
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} while (len > 0);
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/* Clamping should not be needed but float rounding errors seem to
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* make this fail on rare occasions. */
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const int index = clamp(first - 1, 0, kernel_data.integrator.num_distribution - 1);
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return index;
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}
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ccl_device bool light_distribution_sample(KernelGlobals kg,
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const float rand,
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ccl_private LightSample *ls)
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{
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/* Sample light index from distribution. */
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ls->emitter_id = light_distribution_sample(kg, rand);
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ls->pdf_selection = kernel_data.integrator.distribution_pdf_lights;
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return true;
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}
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ccl_device_inline float light_distribution_pdf_lamp(KernelGlobals kg)
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{
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return kernel_data.integrator.distribution_pdf_lights;
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}
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CCL_NAMESPACE_END
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