Differential D16655 Diff 58189 intern/cycles/kernel/light/distant.h

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intern/cycles/kernel/light/distant.h

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

				#pragma once

				#include "kernel/geom/geom.h"

				#include "kernel/light/common.h"

				CCL_NAMESPACE_BEGIN

				ccl_device_inline bool distant_light_sample(const ccl_global KernelLight *klight,
				const float randu,
				const float randv,
				ccl_private LightSample *ls)
				{
				/* distant light */
				float3 lightD = klight->co;
				float3 D = lightD;
				float radius = klight->distant.radius;
				float invarea = klight->distant.invarea;

				if (radius > 0.0f) {
				D = normalize(D + disk_light_sample(D, randu, randv) * radius);
				}

				ls->P = D;
				ls->Ng = D;
				ls->D = -D;
				ls->t = FLT_MAX;

				float costheta = dot(lightD, D);
				ls->pdf = invarea / (costheta * costheta * costheta);
				ls->eval_fac = ls->pdf;

				return true;
				}

				ccl_device bool distant_light_sample_from_intersection(KernelGlobals kg,
				const float3 ray_D,
				const int lamp,
				ccl_private LightSample *ccl_restrict ls)
				{
				ccl_global const KernelLight *klight = &kernel_data_fetch(lights, lamp);
				const int shader = klight->shader_id;
				const float radius = klight->distant.radius;
				const LightType type = (LightType)klight->type;

				if (type != LIGHT_DISTANT) {
				return false;
				}
				if (!(shader & SHADER_USE_MIS)) {
				return false;
				}
				if (radius == 0.0f) {
				return false;
				}

				/* a distant light is infinitely far away, but equivalent to a disk
				* shaped light exactly 1 unit away from the current shading point.
				*
				* radius t^2/cos(theta)
				* <----------> t = sqrt(1^2 + tan(theta)^2)
				* tan(th) area = radiusradiuspi
				* <----->
				* \ \| (1 + tan(theta)^2)/cos(theta)
				* \ \| (1 + tan(acos(cos(theta)))^2)/cos(theta)
				* t \th\| 1 simplifies to
				* \-\| 1/(cos(theta)^3)
				* \\| magic!
				* P
				*/

				float3 lightD = klight->co;
				float costheta = dot(-lightD, ray_D);
				float cosangle = klight->distant.cosangle;

				/* Workaround to prevent a hang in the classroom scene with AMD HIP drivers 22.10,
				* Remove when a compiler fix is available. */
				#ifdef __HIP__
				ls->shader = klight->shader_id;
				#endif

				if (costheta < cosangle)
				return false;

				ls->type = type;
				#ifndef __HIP__
				ls->shader = klight->shader_id;
				#endif
				ls->object = PRIM_NONE;
				ls->prim = PRIM_NONE;
				ls->lamp = lamp;
				/* todo: missing texture coordinates */
				ls->u = 0.0f;
				ls->v = 0.0f;
				ls->t = FLT_MAX;
				ls->P = -ray_D;
				ls->Ng = -ray_D;
				ls->D = ray_D;
				ls->group = lamp_lightgroup(kg, lamp);

				/* compute pdf */
				float invarea = klight->distant.invarea;
				ls->pdf = invarea / (costheta * costheta * costheta);
				ls->eval_fac = ls->pdf;

				return true;
				}
				CCL_NAMESPACE_END