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blender/intern/cycles/kernel/kernel_light.h

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/*
* Copyright 2011-2013 Blender Foundation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "kernel_light_background.h"
CCL_NAMESPACE_BEGIN
/* Light Sample result */
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 */
LightType type; /* type of light */
} LightSample;
/* Regular Light */
ccl_device_inline bool lamp_light_sample(
KernelGlobals *kg, int lamp, float randu, float randv, float3 P, LightSample *ls)
{
const ccl_global KernelLight *klight = &kernel_tex_fetch(__lights, lamp);
LightType type = (LightType)klight->type;
ls->type = type;
ls->shader = klight->shader_id;
ls->object = PRIM_NONE;
ls->prim = PRIM_NONE;
ls->lamp = lamp;
ls->u = randu;
ls->v = randv;
if (type == LIGHT_DISTANT) {
/* distant light */
float3 lightD = make_float3(klight->co[0], klight->co[1], klight->co[2]);
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;
}
#ifdef __BACKGROUND_MIS__
else if (type == LIGHT_BACKGROUND) {
/* infinite area light (e.g. light dome or env light) */
float3 D = -background_light_sample(kg, P, randu, randv, &ls->pdf);
ls->P = D;
ls->Ng = D;
ls->D = -D;
ls->t = FLT_MAX;
ls->eval_fac = 1.0f;
}
#endif
else {
ls->P = make_float3(klight->co[0], klight->co[1], klight->co[2]);
if (type == LIGHT_POINT || type == LIGHT_SPOT) {
float radius = klight->spot.radius;
if (radius > 0.0f)
/* sphere light */
ls->P += sphere_light_sample(P, ls->P, radius, randu, randv);
ls->D = normalize_len(ls->P - P, &ls->t);
ls->Ng = -ls->D;
float invarea = klight->spot.invarea;
ls->eval_fac = (0.25f * M_1_PI_F) * invarea;
ls->pdf = invarea;
if (type == LIGHT_SPOT) {
/* spot light attenuation */
float3 dir = make_float3(klight->spot.dir[0], klight->spot.dir[1], klight->spot.dir[2]);
ls->eval_fac *= spot_light_attenuation(
dir, klight->spot.spot_angle, klight->spot.spot_smooth, ls->Ng);
if (ls->eval_fac == 0.0f) {
return false;
}
}
float2 uv = map_to_sphere(ls->Ng);
ls->u = uv.x;
ls->v = uv.y;
ls->pdf *= lamp_light_pdf(kg, ls->Ng, -ls->D, ls->t);
}
else {
/* area light */
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]);
float invarea = fabsf(klight->area.invarea);
bool is_round = (klight->area.invarea < 0.0f);
if (dot(ls->P - P, Ng) > 0.0f) {
return false;
}
float3 inplane;
if (is_round) {
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 (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;
}
ls->u = dot(inplane, axisu) * (1.0f / dot(axisu, axisu)) + 0.5f;
ls->v = dot(inplane, axisv) * (1.0f / dot(axisv, axisv)) + 0.5f;
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 (ls->pdf > 0.0f);
}
ccl_device bool lamp_light_eval(
KernelGlobals *kg, int lamp, float3 P, float3 D, float t, LightSample *ls)
{
const ccl_global KernelLight *klight = &kernel_tex_fetch(__lights, lamp);
LightType type = (LightType)klight->type;
ls->type = type;
ls->shader = klight->shader_id;
ls->object = PRIM_NONE;
ls->prim = PRIM_NONE;
ls->lamp = lamp;
/* todo: missing texture coordinates */
ls->u = 0.0f;
ls->v = 0.0f;
if (!(ls->shader & SHADER_USE_MIS))
return false;
if (type == LIGHT_DISTANT) {
/* distant light */
float radius = klight->distant.radius;
if (radius == 0.0f)
return false;
if (t != FLT_MAX)
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 = radius*radius*pi
* <----->
* \ | (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, D);
float cosangle = klight->distant.cosangle;
if (costheta < cosangle)
return false;
ls->P = -D;
ls->Ng = -D;
ls->D = D;
ls->t = FLT_MAX;
/* compute pdf */
float invarea = klight->distant.invarea;
ls->pdf = invarea / (costheta * costheta * costheta);
ls->eval_fac = ls->pdf;
}
else if (type == LIGHT_POINT || type == LIGHT_SPOT) {
float3 lightP = make_float3(klight->co[0], klight->co[1], klight->co[2]);
float radius = klight->spot.radius;
/* sphere light */
if (radius == 0.0f)
return false;
if (!ray_aligned_disk_intersect(P, D, t, lightP, radius, &ls->P, &ls->t)) {
return false;
}
ls->Ng = -D;
ls->D = D;
float invarea = klight->spot.invarea;
ls->eval_fac = (0.25f * M_1_PI_F) * invarea;
ls->pdf = invarea;
if (type == LIGHT_SPOT) {
/* spot light attenuation */
float3 dir = make_float3(klight->spot.dir[0], klight->spot.dir[1], klight->spot.dir[2]);
ls->eval_fac *= spot_light_attenuation(
dir, klight->spot.spot_angle, klight->spot.spot_smooth, ls->Ng);
if (ls->eval_fac == 0.0f)
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, ls->Ng, -ls->D, ls->t);
}
else if (type == LIGHT_AREA) {
/* area light */
float invarea = fabsf(klight->area.invarea);
bool is_round = (klight->area.invarea < 0.0f);
if (invarea == 0.0f)
return false;
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]);
/* one sided */
if (dot(D, Ng) >= 0.0f)
return false;
float3 light_P = make_float3(klight->co[0], klight->co[1], klight->co[2]);
if (!ray_quad_intersect(
P, D, 0.0f, t, light_P, axisu, axisv, Ng, &ls->P, &ls->t, &ls->u, &ls->v, is_round)) {
return false;
}
ls->D = D;
ls->Ng = Ng;
if (is_round) {
ls->pdf = invarea * lamp_light_pdf(kg, Ng, -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(
P, Ng, &light_P, &sample_axisu, &sample_axisv, klight->area.tan_spread)) {
return false;
}
}
ls->pdf = rect_light_sample(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 {
return false;
}
ls->pdf *= kernel_data.integrator.pdf_lights;
return true;
}
/* Triangle Light */
/* 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_tex_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,
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, 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;
}
}
ccl_device_forceinline void triangle_light_sample(KernelGlobals *kg,
int prim,
int object,
float randu,
float randv,
float time,
LightSample *ls,
const float3 P)
{
/* 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, 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_tex_fetch(__object_flag, object);
if (object_flag & SD_OBJECT_NEGATIVE_SCALE_APPLIED) {
ls->Ng = -ls->Ng;
}
ls->eval_fac = 1.0f;
ls->shader = kernel_tex_fetch(__tri_shader, prim);
ls->object = object;
ls->prim = prim;
ls->lamp = LAMP_NONE;
ls->shader |= SHADER_USE_MIS;
ls->type = LIGHT_TRIANGLE;
float distance_to_plane = fabsf(dot(N0, V[0] - P) / dot(N0, N0));
if (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,
FLT_MAX,
#if defined(__KERNEL_SSE2__) && defined(__KERNEL_SSE__)
(ssef *)V,
#else
V[0],
V[1],
V[2],
#endif
&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;
ls->P = u * V[0] + v * V[1] + t * V[2];
/* 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;
ls->v = v;
}
}
/* Light Distribution */
ccl_device int light_distribution_sample(KernelGlobals *kg, 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_tex_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
* each area light be stratified as well. */
float distr_min = kernel_tex_fetch(__light_distribution, index).totarea;
float distr_max = kernel_tex_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)
{
return (bounce > kernel_tex_fetch(__lights, index).max_bounces);
}
ccl_device_noinline bool light_sample(KernelGlobals *kg,
int lamp,
float randu,
float randv,
float time,
float3 P,
int bounce,
LightSample *ls)
{
if (lamp < 0) {
/* sample index */
int index = light_distribution_sample(kg, &randu);
/* fetch light data */
const ccl_global KernelLightDistribution *kdistribution = &kernel_tex_fetch(
__light_distribution, index);
int prim = kdistribution->prim;
if (prim >= 0) {
int object = kdistribution->mesh_light.object_id;
int shader_flag = kdistribution->mesh_light.shader_flag;
triangle_light_sample(kg, prim, object, randu, randv, time, ls, P);
ls->shader |= shader_flag;
return (ls->pdf > 0.0f);
}
lamp = -prim - 1;
}
if (UNLIKELY(light_select_reached_max_bounces(kg, lamp, bounce))) {
return false;
}
return lamp_light_sample(kg, lamp, randu, randv, P, ls);
}
ccl_device_inline int light_select_num_samples(KernelGlobals *kg, int index)
{
return kernel_tex_fetch(__lights, index).samples;
}
CCL_NAMESPACE_END
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