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

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intern/cycles/kernel/light/light.h

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

#pragma once		#pragma once

#include "kernel/geom/geom.h"		#include "kernel/light/area.h"
#include "kernel/light/background.h"		#include "kernel/light/background.h"
		#include "kernel/light/distant.h"
		#include "kernel/light/point.h"
		#include "kernel/light/spot.h"
		#include "kernel/light/triangle.h"

#include "kernel/sample/mapping.h"		#include "kernel/sample/mapping.h"

CCL_NAMESPACE_BEGIN		CCL_NAMESPACE_BEGIN

/* Light Sample result */		/* Sample point on an individual light. */

typedef struct LightSample {
float3 P; /* position on light, or direction for distant light */
float3 Ng; /* normal on light */
float3 D; /* direction from shading point to light */
float t; /* distance to light (FLT_MAX for distant light) */
float u, v; /* parametric coordinate on primitive */
float pdf; /* light sampling probability density function */
float eval_fac; /* intensity multiplier */
int object; /* object id for triangle/curve lights */
int prim; /* primitive id for triangle/curve lights */
int shader; /* shader id */
int lamp; /* lamp id */
int group; /* lightgroup */
LightType type; /* type of light */
} LightSample;

/* Regular Light */

template<bool in_volume_segment>		template<bool in_volume_segment>
ccl_device_inline bool light_sample(KernelGlobals kg,		ccl_device_inline bool light_sample(KernelGlobals kg,
const int lamp,		const int lamp,
const float randu,		const float randu,
const float randv,		const float randv,
const float3 P,		const float3 P,
const uint32_t path_flag,		const uint32_t path_flag,
Show All 24 Lines	if (in_volume_segment && (type == LIGHT_DISTANT \|\| type == LIGHT_BACKGROUND)) {
ls->Ng = zero_float3();		ls->Ng = zero_float3();
ls->D = zero_float3();		ls->D = zero_float3();
ls->pdf = 1.0f;		ls->pdf = 1.0f;
ls->t = FLT_MAX;		ls->t = FLT_MAX;
return true;		return true;
}		}

if (type == LIGHT_DISTANT) {		if (type == LIGHT_DISTANT) {
/* distant light */		if (!distant_light_sample(klight, randu, randv, ls)) {
float3 lightD = make_float3(klight->co[0], klight->co[1], klight->co[2]);		return false;
float3 D = lightD;		}
float radius = klight->distant.radius;
float invarea = klight->distant.invarea;

if (radius > 0.0f)
D = distant_light_sample(D, radius, randu, randv);

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;
}		}
else if (type == LIGHT_BACKGROUND) {		else if (type == LIGHT_BACKGROUND) {
/* infinite area light (e.g. light dome or env light) */		/* infinite area light (e.g. light dome or env light) */
float3 D = -background_light_sample(kg, P, randu, randv, &ls->pdf);		float3 D = -background_light_sample(kg, P, randu, randv, &ls->pdf);

ls->P = D;		ls->P = D;
ls->Ng = D;		ls->Ng = D;
ls->D = -D;		ls->D = -D;
ls->t = FLT_MAX;		ls->t = FLT_MAX;
ls->eval_fac = 1.0f;		ls->eval_fac = 1.0f;
}		}
else {		else if (type == LIGHT_SPOT) {
ls->P = make_float3(klight->co[0], klight->co[1], klight->co[2]);		if (!spot_light_sample<in_volume_segment>(klight, randu, randv, P, ls)) {

if (type == LIGHT_SPOT) {
const float3 center = make_float3(klight->co[0], klight->co[1], klight->co[2]);
const float radius = klight->spot.radius;
const float3 dir = make_float3(
klight->spot.dir[0], klight->spot.dir[1], klight->spot.dir[2]);
/* disk oriented normal */
const float3 lightN = normalize(P - center);
ls->P = center;

if (radius > 0.0f)
/* disk light */
ls->P += disk_light_sample(lightN, randu, randv) * radius;

const float invarea = klight->spot.invarea;
ls->pdf = invarea;

ls->D = normalize_len(ls->P - P, &ls->t);
/* we set the light normal to the outgoing direction to support texturing */
ls->Ng = -ls->D;

ls->eval_fac = (0.25f * M_1_PI_F) * invarea;

/* spot light attenuation */
ls->eval_fac *= spot_light_attenuation(
dir, klight->spot.spot_angle, klight->spot.spot_smooth, -ls->D);
if (!in_volume_segment && ls->eval_fac == 0.0f) {
return false;		return false;
}		}

float2 uv = map_to_sphere(ls->Ng);
ls->u = uv.x;
ls->v = uv.y;

ls->pdf *= lamp_light_pdf(kg, lightN, -ls->D, ls->t);
}		}
else if (type == LIGHT_POINT) {		else if (type == LIGHT_POINT) {
float3 center = make_float3(klight->co[0], klight->co[1], klight->co[2]);		if (!point_light_sample<in_volume_segment>(klight, randu, randv, P, ls)) {
float radius = klight->spot.radius;
/* disk oriented normal */
const float3 lightN = normalize(P - center);
ls->P = center;

if (radius > 0.0f) {
ls->P += disk_light_sample(lightN, randu, randv) * radius;
}
ls->pdf = klight->spot.invarea;

ls->D = normalize_len(ls->P - P, &ls->t);
/* we set the light normal to the outgoing direction to support texturing */
ls->Ng = -ls->D;

ls->eval_fac = M_1_PI_F * 0.25f * klight->spot.invarea;
if (!in_volume_segment && ls->eval_fac == 0.0f) {
return false;		return false;
}		}

float2 uv = map_to_sphere(ls->Ng);
ls->u = uv.x;
ls->v = uv.y;
ls->pdf *= lamp_light_pdf(kg, lightN, -ls->D, ls->t);
}		}
else {		else {
/* area light */		/* area light */
float3 axisu = make_float3(		if (!area_light_sample<in_volume_segment>(klight, randu, randv, P, ls)) {
klight->area.axisu[0], klight->area.axisu[1], klight->area.axisu[2]);
float3 axisv = make_float3(
klight->area.axisv[0], klight->area.axisv[1], klight->area.axisv[2]);
float3 Ng = make_float3(klight->area.dir[0], klight->area.dir[1], klight->area.dir[2]);
float invarea = fabsf(klight->area.invarea);
bool is_round = (klight->area.invarea < 0.0f);

if (!in_volume_segment) {
if (dot(ls->P - P, Ng) > 0.0f) {
return false;		return false;
}		}
}		}

float3 inplane;

if (is_round \|\| in_volume_segment) {
inplane = ellipse_sample(axisu * 0.5f, axisv * 0.5f, randu, randv);
ls->P += inplane;
ls->pdf = invarea;
}
else {
inplane = ls->P;

float3 sample_axisu = axisu;
float3 sample_axisv = axisv;

if (!in_volume_segment && klight->area.tan_spread > 0.0f) {
if (!light_spread_clamp_area_light(
P, Ng, &ls->P, &sample_axisu, &sample_axisv, klight->area.tan_spread)) {
return false;
}
}

ls->pdf = rect_light_sample(P, &ls->P, sample_axisu, sample_axisv, randu, randv, true);
inplane = ls->P - inplane;
}

const float light_u = dot(inplane, axisu) * (1.0f / dot(axisu, axisu));
const float light_v = dot(inplane, axisv) * (1.0f / dot(axisv, axisv));

/* NOTE: Return barycentric coordinates in the same notation as Embree and OptiX. */
ls->u = light_v + 0.5f;
ls->v = -light_u - light_v;

ls->Ng = Ng;
ls->D = normalize_len(ls->P - P, &ls->t);

ls->eval_fac = 0.25f * invarea;

if (klight->area.tan_spread > 0.0f) {
/* Area Light spread angle attenuation */
ls->eval_fac *= light_spread_attenuation(
ls->D, ls->Ng, klight->area.tan_spread, klight->area.normalize_spread);
}

if (is_round) {
ls->pdf *= lamp_light_pdf(kg, Ng, -ls->D, ls->t);
}
}
}

ls->pdf *= kernel_data.integrator.pdf_lights;

return in_volume_segment \|\| (ls->pdf > 0.0f);		return in_volume_segment \|\| (ls->pdf > 0.0f);
}		}

		/* Intersect ray with individual light. */

ccl_device bool lights_intersect(KernelGlobals kg,		ccl_device bool lights_intersect(KernelGlobals kg,
IntegratorState state,		IntegratorState state,
ccl_private const Ray *ccl_restrict ray,		ccl_private const Ray *ccl_restrict ray,
ccl_private Intersection *ccl_restrict isect,		ccl_private Intersection *ccl_restrict isect,
const int last_prim,		const int last_prim,
const int last_object,		const int last_object,
const int last_type,		const int last_type,
const uint32_t path_flag)		const uint32_t path_flag)
{		{
for (int lamp = 0; lamp < kernel_data.integrator.num_all_lights; lamp++) {		for (int lamp = 0; lamp < kernel_data.integrator.num_lights; lamp++) {
const ccl_global KernelLight *klight = &kernel_data_fetch(lights, lamp);		const ccl_global KernelLight *klight = &kernel_data_fetch(lights, lamp);

if (path_flag & PATH_RAY_CAMERA) {		if (path_flag & PATH_RAY_CAMERA) {
if (klight->shader_id & SHADER_EXCLUDE_CAMERA) {		if (klight->shader_id & SHADER_EXCLUDE_CAMERA) {
continue;		continue;
}		}
}		}
else {		else {
Show All 16 Lines	if (path_flag & PATH_RAY_SHADOW_CATCHER_PASS) {
continue;		continue;
}		}
}		}

LightType type = (LightType)klight->type;		LightType type = (LightType)klight->type;
float t = 0.0f, u = 0.0f, v = 0.0f;		float t = 0.0f, u = 0.0f, v = 0.0f;

if (type == LIGHT_SPOT) {		if (type == LIGHT_SPOT) {
/* Spot/Disk light. */		if (!spot_light_intersect(klight, ray, &t)) {
const float3 lightP = make_float3(klight->co[0], klight->co[1], klight->co[2]);
const float radius = klight->spot.radius;
if (radius == 0.0f) {
continue;
}
/* disk oriented normal */
const float3 lightN = normalize(ray->P - lightP);
/* One sided. */
if (dot(ray->D, lightN) >= 0.0f) {
continue;
}

float3 P;
if (!ray_disk_intersect(
ray->P, ray->D, ray->tmin, ray->tmax, lightP, lightN, radius, &P, &t)) {
continue;		continue;
}		}
}		}
else if (type == LIGHT_POINT) {		else if (type == LIGHT_POINT) {
/* Sphere light (aka, aligned disk light). */		if (!point_light_intersect(klight, ray, &t)) {
const float3 lightP = make_float3(klight->co[0], klight->co[1], klight->co[2]);
const float radius = klight->spot.radius;
if (radius == 0.0f) {
continue;
}

/* disk oriented normal */
const float3 lightN = normalize(ray->P - lightP);
float3 P;
if (!ray_disk_intersect(
ray->P, ray->D, ray->tmin, ray->tmax, lightP, lightN, radius, &P, &t)) {
continue;		continue;
}		}
}		}
else if (type == LIGHT_AREA) {		else if (type == LIGHT_AREA) {
/* Area light. */		if (!area_light_intersect(klight, ray, &t, &u, &v)) {
const float invarea = fabsf(klight->area.invarea);
const bool is_round = (klight->area.invarea < 0.0f);
if (invarea == 0.0f) {
continue;
}

const float3 axisu = make_float3(
klight->area.axisu[0], klight->area.axisu[1], klight->area.axisu[2]);
const float3 axisv = make_float3(
klight->area.axisv[0], klight->area.axisv[1], klight->area.axisv[2]);
const float3 Ng = make_float3(klight->area.dir[0], klight->area.dir[1], klight->area.dir[2]);

/* One sided. */
if (dot(ray->D, Ng) >= 0.0f) {
continue;
}

const float3 light_P = make_float3(klight->co[0], klight->co[1], klight->co[2]);

float3 P;
if (!ray_quad_intersect(ray->P,
ray->D,
ray->tmin,
ray->tmax,
light_P,
axisu,
axisv,
Ng,
&P,
&t,
&u,
&v,
is_round)) {
continue;		continue;
}		}
}		}
else {		else {
continue;		continue;
}		}

if (t < isect->t &&		if (t < isect->t &&
!(last_prim == lamp && last_object == OBJECT_NONE && last_type == PRIMITIVE_LAMP)) {		!(last_prim == lamp && last_object == OBJECT_NONE && last_type == PRIMITIVE_LAMP)) {
isect->t = t;		isect->t = t;
isect->u = u;		isect->u = u;
isect->v = v;		isect->v = v;
isect->type = PRIMITIVE_LAMP;		isect->type = PRIMITIVE_LAMP;
isect->prim = lamp;		isect->prim = lamp;
isect->object = OBJECT_NONE;		isect->object = OBJECT_NONE;
}		}
}		}

return isect->prim != PRIM_NONE;		return isect->prim != PRIM_NONE;
}		}

ccl_device bool light_sample_from_distant_ray(KernelGlobals kg,		/* Setup light sample from intersection. */
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 = make_float3(klight->co[0], klight->co[1], klight->co[2]);
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;
ls->pdf *= kernel_data.integrator.pdf_lights;

return true;
}

ccl_device bool light_sample_from_intersection(KernelGlobals kg,		ccl_device bool light_sample_from_intersection(KernelGlobals kg,
ccl_private const Intersection *ccl_restrict isect,		ccl_private const Intersection *ccl_restrict isect,
const float3 ray_P,		const float3 ray_P,
const float3 ray_D,		const float3 ray_D,
ccl_private LightSample *ccl_restrict ls)		ccl_private LightSample *ccl_restrict ls)
{		{
const int lamp = isect->prim;		const int lamp = isect->prim;
ccl_global const KernelLight *klight = &kernel_data_fetch(lights, lamp);		ccl_global const KernelLight *klight = &kernel_data_fetch(lights, lamp);
LightType type = (LightType)klight->type;		LightType type = (LightType)klight->type;
ls->type = type;		ls->type = type;
ls->shader = klight->shader_id;		ls->shader = klight->shader_id;
ls->object = isect->object;		ls->object = isect->object;
ls->prim = isect->prim;		ls->prim = isect->prim;
ls->lamp = lamp;		ls->lamp = lamp;
/* todo: missing texture coordinates */		/* todo: missing texture coordinates */
ls->t = isect->t;		ls->t = isect->t;
ls->P = ray_P + ray_D * ls->t;		ls->P = ray_P + ray_D * ls->t;
ls->D = ray_D;		ls->D = ray_D;
ls->group = lamp_lightgroup(kg, lamp);		ls->group = lamp_lightgroup(kg, lamp);

if (type == LIGHT_SPOT) {		if (type == LIGHT_SPOT) {
const float3 center = make_float3(klight->co[0], klight->co[1], klight->co[2]);		if (!spot_light_sample_from_intersection(klight, isect, ray_P, ray_D, ls)) {
const float3 dir = make_float3(klight->spot.dir[0], klight->spot.dir[1], klight->spot.dir[2]);
/* the normal of the oriented disk */
const float3 lightN = normalize(ray_P - center);
/* We set the light normal to the outgoing direction to support texturing. */
ls->Ng = -ls->D;

float invarea = klight->spot.invarea;
ls->eval_fac = (0.25f * M_1_PI_F) * invarea;
ls->pdf = invarea;

/* spot light attenuation */
ls->eval_fac *= spot_light_attenuation(
dir, klight->spot.spot_angle, klight->spot.spot_smooth, -ls->D);

if (ls->eval_fac == 0.0f) {
return false;		return false;
}		}

float2 uv = map_to_sphere(ls->Ng);
ls->u = uv.x;
ls->v = uv.y;

/* compute pdf */
if (ls->t != FLT_MAX)
ls->pdf *= lamp_light_pdf(kg, lightN, -ls->D, ls->t);
else
ls->pdf = 0.f;
}		}
else if (type == LIGHT_POINT) {		else if (type == LIGHT_POINT) {
const float3 center = make_float3(klight->co[0], klight->co[1], klight->co[2]);		if (!point_light_sample_from_intersection(klight, isect, ray_P, ray_D, ls)) {
const float3 lighN = normalize(ray_P - center);

/* We set the light normal to the outgoing direction to support texturing. */
ls->Ng = -ls->D;

float invarea = klight->spot.invarea;
ls->eval_fac = (0.25f * M_1_PI_F) * invarea;
ls->pdf = invarea;

if (ls->eval_fac == 0.0f) {
return false;		return false;
}		}

float2 uv = map_to_sphere(ls->Ng);
ls->u = uv.x;
ls->v = uv.y;

/* compute pdf */
if (ls->t != FLT_MAX)
ls->pdf *= lamp_light_pdf(kg, lighN, -ls->D, ls->t);
else
ls->pdf = 0.f;
}		}
else if (type == LIGHT_AREA) {		else if (type == LIGHT_AREA) {
/* area light */		if (!area_light_sample_from_intersection(klight, isect, ray_P, ray_D, ls)) {
float invarea = fabsf(klight->area.invarea);

float3 axisu = make_float3(
klight->area.axisu[0], klight->area.axisu[1], klight->area.axisu[2]);
float3 axisv = make_float3(
klight->area.axisv[0], klight->area.axisv[1], klight->area.axisv[2]);
float3 Ng = make_float3(klight->area.dir[0], klight->area.dir[1], klight->area.dir[2]);
float3 light_P = make_float3(klight->co[0], klight->co[1], klight->co[2]);

ls->u = isect->u;
ls->v = isect->v;
ls->D = ray_D;
ls->Ng = Ng;

const bool is_round = (klight->area.invarea < 0.0f);
if (is_round) {
ls->pdf = invarea * lamp_light_pdf(kg, Ng, -ray_D, ls->t);
}
else {
float3 sample_axisu = axisu;
float3 sample_axisv = axisv;

if (klight->area.tan_spread > 0.0f) {
if (!light_spread_clamp_area_light(
ray_P, Ng, &light_P, &sample_axisu, &sample_axisv, klight->area.tan_spread)) {
return false;		return false;
}		}
}		}

ls->pdf = rect_light_sample(ray_P, &light_P, sample_axisu, sample_axisv, 0, 0, false);
}
ls->eval_fac = 0.25f * invarea;

if (klight->area.tan_spread > 0.0f) {
/* Area Light spread angle attenuation */
ls->eval_fac *= light_spread_attenuation(
ls->D, ls->Ng, klight->area.tan_spread, klight->area.normalize_spread);
if (ls->eval_fac == 0.0f) {
return false;
}
}
}
else {		else {
kernel_assert(!"Invalid lamp type in light_sample_from_intersection");		kernel_assert(!"Invalid lamp type in light_sample_from_intersection");
return false;		return false;
}		}

ls->pdf *= kernel_data.integrator.pdf_lights;

return true;		return true;
}		}

/* Triangle Light */		/* Update light sample for changed new position, for MNEE. */

/* returns true if the triangle is has motion blur or an instancing transform applied */
ccl_device_inline bool triangle_world_space_vertices(
KernelGlobals kg, int object, int prim, float time, float3 V[3])
{
bool has_motion = false;
const int object_flag = kernel_data_fetch(object_flag, object);

if (object_flag & SD_OBJECT_HAS_VERTEX_MOTION && time >= 0.0f) {
motion_triangle_vertices(kg, object, prim, time, V);
has_motion = true;
}
else {
triangle_vertices(kg, prim, V);
}

if (!(object_flag & SD_OBJECT_TRANSFORM_APPLIED)) {
#ifdef __OBJECT_MOTION__
float object_time = (time >= 0.0f) ? time : 0.5f;
Transform tfm = object_fetch_transform_motion_test(kg, object, object_time, NULL);
#else
Transform tfm = object_fetch_transform(kg, object, OBJECT_TRANSFORM);
#endif
V[0] = transform_point(&tfm, V[0]);
V[1] = transform_point(&tfm, V[1]);
V[2] = transform_point(&tfm, V[2]);
has_motion = true;
}
return has_motion;
}

ccl_device_inline float triangle_light_pdf_area(KernelGlobals kg,		ccl_device_forceinline void light_update_position(KernelGlobals kg,
const float3 Ng,
const float3 I,
float t)
{
float pdf = kernel_data.integrator.pdf_triangles;
float cos_pi = fabsf(dot(Ng, I));

if (cos_pi == 0.0f)
return 0.0f;

return t * t * pdf / cos_pi;
}

ccl_device_forceinline float triangle_light_pdf(KernelGlobals kg,
ccl_private const ShaderData *sd,
float t)
{
/* A naive heuristic to decide between costly solid angle sampling
* and simple area sampling, comparing the distance to the triangle plane
* to the length of the edges of the triangle. */

float3 V[3];
bool has_motion = triangle_world_space_vertices(kg, sd->object, sd->prim, sd->time, V);

const float3 e0 = V[1] - V[0];
const float3 e1 = V[2] - V[0];
const float3 e2 = V[2] - V[1];
const float longest_edge_squared = max(len_squared(e0), max(len_squared(e1), len_squared(e2)));
const float3 N = cross(e0, e1);
const float distance_to_plane = fabsf(dot(N, sd->I * t)) / dot(N, N);

if (longest_edge_squared > distance_to_plane * distance_to_plane) {
/* sd contains the point on the light source
* calculate Px, the point that we're shading */
const float3 Px = sd->P + sd->I * t;
const float3 v0_p = V[0] - Px;
const float3 v1_p = V[1] - Px;
const float3 v2_p = V[2] - Px;

const float3 u01 = safe_normalize(cross(v0_p, v1_p));
const float3 u02 = safe_normalize(cross(v0_p, v2_p));
const float3 u12 = safe_normalize(cross(v1_p, v2_p));

const float alpha = fast_acosf(dot(u02, u01));
const float beta = fast_acosf(-dot(u01, u12));
const float gamma = fast_acosf(dot(u02, u12));
const float solid_angle = alpha + beta + gamma - M_PI_F;

/* pdf_triangles is calculated over triangle area, but we're not sampling over its area */
if (UNLIKELY(solid_angle == 0.0f)) {
return 0.0f;
}
else {
float area = 1.0f;
if (has_motion) {
/* get the center frame vertices, this is what the PDF was calculated from */
triangle_world_space_vertices(kg, sd->object, sd->prim, -1.0f, V);
area = triangle_area(V[0], V[1], V[2]);
}
else {
area = 0.5f * len(N);
}
const float pdf = area * kernel_data.integrator.pdf_triangles;
return pdf / solid_angle;
}
}
else {
float pdf = triangle_light_pdf_area(kg, sd->Ng, sd->I, t);
if (has_motion) {
const float area = 0.5f * len(N);
if (UNLIKELY(area == 0.0f)) {
return 0.0f;
}
/* scale the PDF.
* area = the area the sample was taken from
* area_pre = the are from which pdf_triangles was calculated from */
triangle_world_space_vertices(kg, sd->object, sd->prim, -1.0f, V);
const float area_pre = triangle_area(V[0], V[1], V[2]);
pdf = pdf * area_pre / area;
}
return pdf;
}
}

template<bool in_volume_segment>
ccl_device_forceinline void triangle_light_sample(KernelGlobals kg,
int prim,
int object,
float randu,
float randv,
float time,
ccl_private LightSample *ls,		ccl_private LightSample *ls,
const float3 P)		const float3 P)
{		{
/* A naive heuristic to decide between costly solid angle sampling		const ccl_global KernelLight *klight = &kernel_data_fetch(lights, ls->lamp);
* and simple area sampling, comparing the distance to the triangle plane
* to the length of the edges of the triangle. */

float3 V[3];
bool has_motion = triangle_world_space_vertices(kg, object, prim, time, V);

const float3 e0 = V[1] - V[0];
const float3 e1 = V[2] - V[0];
const float3 e2 = V[2] - V[1];
const float longest_edge_squared = max(len_squared(e0), max(len_squared(e1), len_squared(e2)));
const float3 N0 = cross(e0, e1);
float Nl = 0.0f;
ls->Ng = safe_normalize_len(N0, &Nl);
float area = 0.5f * Nl;

/* flip normal if necessary */
const int object_flag = kernel_data_fetch(object_flag, object);
if (object_flag & SD_OBJECT_NEGATIVE_SCALE_APPLIED) {
ls->Ng = -ls->Ng;
}
ls->eval_fac = 1.0f;
ls->shader = kernel_data_fetch(tri_shader, prim);
ls->object = object;
ls->prim = prim;
ls->lamp = LAMP_NONE;
ls->shader \|= SHADER_USE_MIS;
ls->type = LIGHT_TRIANGLE;
ls->group = object_lightgroup(kg, object);

float distance_to_plane = fabsf(dot(N0, V[0] - P) / dot(N0, N0));

if (!in_volume_segment && (longest_edge_squared > distance_to_plane * distance_to_plane)) {
/* see James Arvo, "Stratified Sampling of Spherical Triangles"
* http://www.graphics.cornell.edu/pubs/1995/Arv95c.pdf */

/* project the triangle to the unit sphere
* and calculate its edges and angles */
const float3 v0_p = V[0] - P;
const float3 v1_p = V[1] - P;
const float3 v2_p = V[2] - P;

const float3 u01 = safe_normalize(cross(v0_p, v1_p));
const float3 u02 = safe_normalize(cross(v0_p, v2_p));
const float3 u12 = safe_normalize(cross(v1_p, v2_p));

const float3 A = safe_normalize(v0_p);
const float3 B = safe_normalize(v1_p);
const float3 C = safe_normalize(v2_p);

const float cos_alpha = dot(u02, u01);
const float cos_beta = -dot(u01, u12);
const float cos_gamma = dot(u02, u12);

/* calculate dihedral angles */
const float alpha = fast_acosf(cos_alpha);
const float beta = fast_acosf(cos_beta);
const float gamma = fast_acosf(cos_gamma);
/* the area of the unit spherical triangle = solid angle */
const float solid_angle = alpha + beta + gamma - M_PI_F;

/* precompute a few things
* these could be re-used to take several samples
* as they are independent of randu/randv */
const float cos_c = dot(A, B);
const float sin_alpha = fast_sinf(alpha);
const float product = sin_alpha * cos_c;

/* Select a random sub-area of the spherical triangle
* and calculate the third vertex C_ of that new triangle */
const float phi = randu * solid_angle - alpha;
float s, t;
fast_sincosf(phi, &s, &t);
const float u = t - cos_alpha;
const float v = s + product;

const float3 U = safe_normalize(C - dot(C, A) * A);

float q = 1.0f;
const float det = ((v * s + u * t) * sin_alpha);
if (det != 0.0f) {
q = ((v * t - u * s) * cos_alpha - v) / det;
}
const float temp = max(1.0f - q * q, 0.0f);

const float3 C_ = safe_normalize(q * A + sqrtf(temp) * U);

/* Finally, select a random point along the edge of the new triangle
* That point on the spherical triangle is the sampled ray direction */
const float z = 1.0f - randv * (1.0f - dot(C_, B));
ls->D = z * B + safe_sqrtf(1.0f - z * z) * safe_normalize(C_ - dot(C_, B) * B);

/* calculate intersection with the planar triangle */
if (!ray_triangle_intersect(
P, ls->D, 0.0f, FLT_MAX, V[0], V[1], V[2], &ls->u, &ls->v, &ls->t)) {
ls->pdf = 0.0f;
return;
}

ls->P = P + ls->D * ls->t;

/* pdf_triangles is calculated over triangle area, but we're sampling over solid angle */
if (UNLIKELY(solid_angle == 0.0f)) {
ls->pdf = 0.0f;
return;
}
else {
if (has_motion) {
/* get the center frame vertices, this is what the PDF was calculated from */
triangle_world_space_vertices(kg, object, prim, -1.0f, V);
area = triangle_area(V[0], V[1], V[2]);
}
const float pdf = area * kernel_data.integrator.pdf_triangles;
ls->pdf = pdf / solid_angle;
}
}
else {
/* compute random point in triangle. From Eric Heitz's "A Low-Distortion Map Between Triangle
* and Square" */
float u = randu;
float v = randv;
if (v > u) {
u *= 0.5f;
v -= u;
}
else {
v *= 0.5f;
u -= v;
}

const float t = 1.0f - u - v;		if (ls->type == LIGHT_POINT) {
ls->P = u * V[0] + v * V[1] + t * V[2];		point_light_update_position(klight, ls, P);
/* compute incoming direction, distance and pdf */
ls->D = normalize_len(ls->P - P, &ls->t);
ls->pdf = triangle_light_pdf_area(kg, ls->Ng, -ls->D, ls->t);
if (has_motion && area != 0.0f) {
/* scale the PDF.
* area = the area the sample was taken from
* area_pre = the are from which pdf_triangles was calculated from */
triangle_world_space_vertices(kg, object, prim, -1.0f, V);
const float area_pre = triangle_area(V[0], V[1], V[2]);
ls->pdf = ls->pdf * area_pre / area;
}		}
ls->u = u;		else if (ls->type == LIGHT_SPOT) {
ls->v = v;		spot_light_update_position(klight, ls, P);
}		}
		else if (ls->type == LIGHT_AREA) {
		area_light_update_position(klight, ls, P);
}		}

/* Light Distribution */

ccl_device int light_distribution_sample(KernelGlobals kg, ccl_private float *randu)
{
/* This is basically std::upper_bound as used by PBRT, to find a point light or
* triangle to emit from, proportional to area. a good improvement would be to
* also sample proportional to power, though it's not so well defined with
* arbitrary shaders. */
int first = 0;
int len = kernel_data.integrator.num_distribution + 1;
float r = *randu;

do {
int half_len = len >> 1;
int middle = first + half_len;

if (r < kernel_data_fetch(light_distribution, middle).totarea) {
len = half_len;
}		}
else {
first = middle + 1;
len = len - half_len - 1;
}
} while (len > 0);

/* Clamping should not be needed but float rounding errors seem to
* make this fail on rare occasions. */
int index = clamp(first - 1, 0, kernel_data.integrator.num_distribution - 1);

/* Rescale to reuse random number. this helps the 2D samples within		/* Light info. */
* each area light be stratified as well. */
float distr_min = kernel_data_fetch(light_distribution, index).totarea;
float distr_max = kernel_data_fetch(light_distribution, index + 1).totarea;
*randu = (r - distr_min) / (distr_max - distr_min);

return index;
}

/* Generic Light */

ccl_device_inline bool light_select_reached_max_bounces(KernelGlobals kg, int index, int bounce)		ccl_device_inline bool light_select_reached_max_bounces(KernelGlobals kg, int index, int bounce)
{		{
return (bounce > kernel_data_fetch(lights, index).max_bounces);		return (bounce > kernel_data_fetch(lights, index).max_bounces);
}		}

template<bool in_volume_segment>
ccl_device_noinline bool light_distribution_sample(KernelGlobals kg,
float randu,
const float randv,
const float time,
const float3 P,
const int bounce,
const uint32_t path_flag,
ccl_private LightSample *ls)
{
/* Sample light index from distribution. */
const int index = light_distribution_sample(kg, &randu);
ccl_global const KernelLightDistribution *kdistribution = &kernel_data_fetch(light_distribution,
index);
const int prim = kdistribution->prim;

if (prim >= 0) {
/* Mesh light. */
const int object = kdistribution->mesh_light.object_id;

/* Exclude synthetic meshes from shadow catcher pass. */
if ((path_flag & PATH_RAY_SHADOW_CATCHER_PASS) &&
!(kernel_data_fetch(object_flag, object) & SD_OBJECT_SHADOW_CATCHER)) {
return false;
}

const int shader_flag = kdistribution->mesh_light.shader_flag;
triangle_light_sample<in_volume_segment>(kg, prim, object, randu, randv, time, ls, P);
ls->shader \|= shader_flag;
return (ls->pdf > 0.0f);
}

const int lamp = -prim - 1;

if (UNLIKELY(light_select_reached_max_bounces(kg, lamp, bounce))) {
return false;
}

return light_sample<in_volume_segment>(kg, lamp, randu, randv, P, path_flag, ls);
}

ccl_device_inline bool light_distribution_sample_from_volume_segment(KernelGlobals kg,
float randu,
const float randv,
const float time,
const float3 P,
const int bounce,
const uint32_t path_flag,
ccl_private LightSample *ls)
{
return light_distribution_sample<true>(kg, randu, randv, time, P, bounce, path_flag, ls);
}

ccl_device_inline bool light_distribution_sample_from_position(KernelGlobals kg,
float randu,
const float randv,
const float time,
const float3 P,
const int bounce,
const uint32_t path_flag,
ccl_private LightSample *ls)
{
return light_distribution_sample<false>(kg, randu, randv, time, P, bounce, path_flag, ls);
}

ccl_device_inline bool light_distribution_sample_new_position(KernelGlobals kg,
const float randu,
const float randv,
const float time,
const float3 P,
ccl_private LightSample *ls)
{
/* Sample a new position on the same light, for volume sampling. */
if (ls->type == LIGHT_TRIANGLE) {
triangle_light_sample<false>(kg, ls->prim, ls->object, randu, randv, time, ls, P);
return (ls->pdf > 0.0f);
}
else {
return light_sample<false>(kg, ls->lamp, randu, randv, P, 0, ls);
}
}

CCL_NAMESPACE_END		CCL_NAMESPACE_END