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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.
*/
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;
/* Area light sampling */
/* Uses the following paper:
*
* Carlos Urena et al.
* An Area-Preserving Parametrization for Spherical Rectangles.
*
* https://www.solidangle.com/research/egsr2013_spherical_rectangle.pdf
*
* Note: light_p is modified when sample_coord is true.
*/
ccl_device_inline float rect_light_sample(float3 P,
float3 *light_p,
float3 axisu, float3 axisv,
float randu, float randv,
bool sample_coord)
{
/* In our name system we're using P for the center,
* which is o in the paper.
*/
float3 corner = *light_p - axisu * 0.5f - axisv * 0.5f;
float axisu_len, axisv_len;
/* Compute local reference system R. */
float3 x = normalize_len(axisu, &axisu_len);
float3 y = normalize_len(axisv, &axisv_len);
float3 z = cross(x, y);
/* Compute rectangle coords in local reference system. */
float3 dir = corner - P;
float z0 = dot(dir, z);
/* Flip 'z' to make it point against Q. */
if(z0 > 0.0f) {
z *= -1.0f;
z0 *= -1.0f;
}
float x0 = dot(dir, x);
float y0 = dot(dir, y);
float x1 = x0 + axisu_len;
float y1 = y0 + axisv_len;
/* Compute internal angles (gamma_i). */
float4 diff = make_float4(x0, y1, x1, y0) - make_float4(x1, y0, x0, y1);
float4 nz = make_float4(y0, x1, y1, x0) * diff;
nz = nz / sqrt(z0 * z0 * diff * diff + nz * nz);
float g0 = safe_acosf(-nz.x * nz.y);
float g1 = safe_acosf(-nz.y * nz.z);
float g2 = safe_acosf(-nz.z * nz.w);
float g3 = safe_acosf(-nz.w * nz.x);
/* Compute predefined constants. */
float b0 = nz.x;
float b1 = nz.z;
float b0sq = b0 * b0;
float k = M_2PI_F - g2 - g3;
/* Compute solid angle from internal angles. */
float S = g0 + g1 - k;
if(sample_coord) {
/* Compute cu. */
float au = randu * S + k;
float fu = (cosf(au) * b0 - b1) / sinf(au);
float cu = 1.0f / sqrtf(fu * fu + b0sq) * (fu > 0.0f ? 1.0f : -1.0f);
cu = clamp(cu, -1.0f, 1.0f);
/* Compute xu. */
float xu = -(cu * z0) / max(sqrtf(1.0f - cu * cu), 1e-7f);
xu = clamp(xu, x0, x1);
/* Compute yv. */
float z0sq = z0 * z0;
float y0sq = y0 * y0;
float y1sq = y1 * y1;
float d = sqrtf(xu * xu + z0sq);
float h0 = y0 / sqrtf(d * d + y0sq);
float h1 = y1 / sqrtf(d * d + y1sq);
float hv = h0 + randv * (h1 - h0), hv2 = hv * hv;
float yv = (hv2 < 1.0f - 1e-6f) ? (hv * d) / sqrtf(1.0f - hv2) : y1;
/* Transform (xu, yv, z0) to world coords. */
*light_p = P + xu * x + yv * y + z0 * z;
}
/* return pdf */
if(S != 0.0f)
return 1.0f / S;
else
return 0.0f;
}
ccl_device_inline float3 ellipse_sample(float3 ru, float3 rv, float randu, float randv)
{
to_unit_disk(&randu, &randv);
return ru*randu + rv*randv;
}
ccl_device float3 disk_light_sample(float3 v, float randu, float randv)
{
float3 ru, rv;
make_orthonormals(v, &ru, &rv);
return ellipse_sample(ru, rv, randu, randv);
}
ccl_device float3 distant_light_sample(float3 D, float radius, float randu, float randv)
{
return normalize(D + disk_light_sample(D, randu, randv)*radius);
}
ccl_device float3 sphere_light_sample(float3 P, float3 center, float radius, float randu, float randv)
{
return disk_light_sample(normalize(P - center), randu, randv)*radius;
}
ccl_device float spot_light_attenuation(float3 dir, float spot_angle, float spot_smooth, LightSample *ls)
{
float3 I = ls->Ng;
float attenuation = dot(dir, I);
if(attenuation <= spot_angle) {
attenuation = 0.0f;
}
else {
float t = attenuation - spot_angle;
if(t < spot_smooth && spot_smooth != 0.0f)
attenuation *= smoothstepf(t/spot_smooth);
}
return attenuation;
}
ccl_device float lamp_light_pdf(KernelGlobals *kg, const float3 Ng, const float3 I, float t)
{
float cos_pi = dot(Ng, I);
if(cos_pi <= 0.0f)
return 0.0f;
return t*t/cos_pi;
}
/* Background Light */
#ifdef __BACKGROUND_MIS__
/* TODO(sergey): In theory it should be all fine to use noinline for all
* devices, but we're so close to the release so better not screw things
* up for CPU at least.
*/
#ifdef __KERNEL_GPU__
ccl_device_noinline
#else
ccl_device
#endif
float3 background_map_sample(KernelGlobals *kg, float randu, float randv, float *pdf)
{
/* for the following, the CDF values are actually a pair of floats, with the
* function value as X and the actual CDF as Y. The last entry's function
* value is the CDF total. */
int res_x = kernel_data.integrator.pdf_background_res_x;
int res_y = kernel_data.integrator.pdf_background_res_y;
int cdf_width = res_x + 1;
/* this is basically std::lower_bound as used by pbrt */
int first = 0;
int count = res_y;
while(count > 0) {
int step = count >> 1;
int middle = first + step;
if(kernel_tex_fetch(__light_background_marginal_cdf, middle).y < randv) {
first = middle + 1;
count -= step + 1;
}
else
count = step;
}
int index_v = max(0, first - 1);
kernel_assert(index_v >= 0 && index_v < res_y);
float2 cdf_v = kernel_tex_fetch(__light_background_marginal_cdf, index_v);
float2 cdf_next_v = kernel_tex_fetch(__light_background_marginal_cdf, index_v + 1);
float2 cdf_last_v = kernel_tex_fetch(__light_background_marginal_cdf, res_y);
/* importance-sampled V direction */
float dv = inverse_lerp(cdf_v.y, cdf_next_v.y, randv);
float v = (index_v + dv) / res_y;
/* this is basically std::lower_bound as used by pbrt */
first = 0;
count = res_x;
while(count > 0) {
int step = count >> 1;
int middle = first + step;
if(kernel_tex_fetch(__light_background_conditional_cdf, index_v * cdf_width + middle).y < randu) {
first = middle + 1;
count -= step + 1;
}
else
count = step;
}
int index_u = max(0, first - 1);
kernel_assert(index_u >= 0 && index_u < res_x);
float2 cdf_u = kernel_tex_fetch(__light_background_conditional_cdf, index_v * cdf_width + index_u);
float2 cdf_next_u = kernel_tex_fetch(__light_background_conditional_cdf, index_v * cdf_width + index_u + 1);
float2 cdf_last_u = kernel_tex_fetch(__light_background_conditional_cdf, index_v * cdf_width + res_x);
/* importance-sampled U direction */
float du = inverse_lerp(cdf_u.y, cdf_next_u.y, randu);
float u = (index_u + du) / res_x;
/* compute pdf */
float denom = cdf_last_u.x * cdf_last_v.x;
float sin_theta = sinf(M_PI_F * v);
if(sin_theta == 0.0f || denom == 0.0f)
*pdf = 0.0f;
else
*pdf = (cdf_u.x * cdf_v.x)/(M_2PI_F * M_PI_F * sin_theta * denom);
/* compute direction */
return equirectangular_to_direction(u, v);
}
/* TODO(sergey): Same as above, after the release we should consider using
* 'noinline' for all devices.
*/
#ifdef __KERNEL_GPU__
ccl_device_noinline
#else
ccl_device
#endif
float background_map_pdf(KernelGlobals *kg, float3 direction)
{
float2 uv = direction_to_equirectangular(direction);
int res_x = kernel_data.integrator.pdf_background_res_x;
int res_y = kernel_data.integrator.pdf_background_res_y;
int cdf_width = res_x + 1;
float sin_theta = sinf(uv.y * M_PI_F);
if(sin_theta == 0.0f)
return 0.0f;
int index_u = clamp(float_to_int(uv.x * res_x), 0, res_x - 1);
int index_v = clamp(float_to_int(uv.y * res_y), 0, res_y - 1);
/* pdfs in V direction */
float2 cdf_last_u = kernel_tex_fetch(__light_background_conditional_cdf, index_v * cdf_width + res_x);
float2 cdf_last_v = kernel_tex_fetch(__light_background_marginal_cdf, res_y);
float denom = cdf_last_u.x * cdf_last_v.x;
if(denom == 0.0f)
return 0.0f;
/* pdfs in U direction */
float2 cdf_u = kernel_tex_fetch(__light_background_conditional_cdf, index_v * cdf_width + index_u);
float2 cdf_v = kernel_tex_fetch(__light_background_marginal_cdf, index_v);
return (cdf_u.x * cdf_v.x)/(M_2PI_F * M_PI_F * sin_theta * denom);
}
ccl_device_inline bool background_portal_data_fetch_and_check_side(KernelGlobals *kg,
float3 P,
int index,
float3 *lightpos,
float3 *dir)
{
int portal = kernel_data.integrator.portal_offset + index;
const ccl_global KernelLight *klight = &kernel_tex_fetch(__lights, portal);
*lightpos = make_float3(klight->co[0], klight->co[1], klight->co[2]);
*dir = make_float3(klight->area.dir[0], klight->area.dir[1], klight->area.dir[2]);
/* Check whether portal is on the right side. */
if(dot(*dir, P - *lightpos) > 1e-4f)
return true;
return false;
}
ccl_device_inline float background_portal_pdf(KernelGlobals *kg,
float3 P,
float3 direction,
int ignore_portal,
bool *is_possible)
{
float portal_pdf = 0.0f;
int num_possible = 0;
for(int p = 0; p < kernel_data.integrator.num_portals; p++) {
if(p == ignore_portal)
continue;
float3 lightpos, dir;
if(!background_portal_data_fetch_and_check_side(kg, P, p, &lightpos, &dir))
continue;
/* There's a portal that could be sampled from this position. */
if(is_possible) {
*is_possible = true;
}
num_possible++;
int portal = kernel_data.integrator.portal_offset + p;
const ccl_global KernelLight *klight = &kernel_tex_fetch(__lights, portal);
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]);
bool is_round = (klight->area.invarea < 0.0f);
if(!ray_quad_intersect(P, direction, 1e-4f, FLT_MAX, lightpos, axisu, axisv, dir, NULL, NULL, NULL, NULL, is_round))
continue;
if(is_round) {
float t;
float3 D = normalize_len(lightpos - P, &t);
portal_pdf += fabsf(klight->area.invarea) * lamp_light_pdf(kg, dir, -D, t);
}
else {
portal_pdf += rect_light_sample(P, &lightpos, axisu, axisv, 0.0f, 0.0f, false);
}
}
if(ignore_portal >= 0) {
/* We have skipped a portal that could be sampled as well. */
num_possible++;
}
return (num_possible > 0)? portal_pdf / num_possible: 0.0f;
}
ccl_device int background_num_possible_portals(KernelGlobals *kg, float3 P)
{
int num_possible_portals = 0;
for(int p = 0; p < kernel_data.integrator.num_portals; p++) {
float3 lightpos, dir;
if(background_portal_data_fetch_and_check_side(kg, P, p, &lightpos, &dir))
num_possible_portals++;
}
return num_possible_portals;
}
ccl_device float3 background_portal_sample(KernelGlobals *kg,
float3 P,
float randu,
float randv,
int num_possible,
int *sampled_portal,
float *pdf)
{
/* Pick a portal, then re-normalize randv. */
randv *= num_possible;
int portal = (int)randv;
randv -= portal;
/* TODO(sergey): Some smarter way of finding portal to sample
* is welcome.
*/
for(int p = 0; p < kernel_data.integrator.num_portals; p++) {
/* Search for the sampled portal. */
float3 lightpos, dir;
if(!background_portal_data_fetch_and_check_side(kg, P, p, &lightpos, &dir))
continue;
if(portal == 0) {
/* p is the portal to be sampled. */
int portal = kernel_data.integrator.portal_offset + p;
const ccl_global KernelLight *klight = &kernel_tex_fetch(__lights, portal);
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]);
bool is_round = (klight->area.invarea < 0.0f);
float3 D;
if(is_round) {
lightpos += ellipse_sample(axisu*0.5f, axisv*0.5f, randu, randv);
float t;
D = normalize_len(lightpos - P, &t);
*pdf = fabsf(klight->area.invarea) * lamp_light_pdf(kg, dir, -D, t);
}
else {
*pdf = rect_light_sample(P, &lightpos,
axisu, axisv,
randu, randv,
true);
D = normalize(lightpos - P);
}
*pdf /= num_possible;
*sampled_portal = p;
return D;
}
portal--;
}
return make_float3(0.0f, 0.0f, 0.0f);
}
ccl_device_inline float3 background_light_sample(KernelGlobals *kg,
float3 P,
float randu, float randv,
float *pdf)
{
/* Probability of sampling portals instead of the map. */
float portal_sampling_pdf = kernel_data.integrator.portal_pdf;
/* Check if there are portals in the scene which we can sample. */
if(portal_sampling_pdf > 0.0f) {
int num_portals = background_num_possible_portals(kg, P);
if(num_portals > 0) {
if(portal_sampling_pdf == 1.0f || randu < portal_sampling_pdf) {
if(portal_sampling_pdf < 1.0f) {
randu /= portal_sampling_pdf;
}
int portal;
float3 D = background_portal_sample(kg, P, randu, randv, num_portals, &portal, pdf);
if(num_portals > 1) {
/* Ignore the chosen portal, its pdf is already included. */
*pdf += background_portal_pdf(kg, P, D, portal, NULL);
}
/* We could also have sampled the map, so combine with MIS. */
if(portal_sampling_pdf < 1.0f) {
float cdf_pdf = background_map_pdf(kg, D);
*pdf = (portal_sampling_pdf * (*pdf)
+ (1.0f - portal_sampling_pdf) * cdf_pdf);
}
return D;
}
else {
/* Sample map, but with nonzero portal_sampling_pdf for MIS. */
randu = (randu - portal_sampling_pdf) / (1.0f - portal_sampling_pdf);
}
}
else {
/* We can't sample a portal.
* Check if we can sample the map instead.
*/
if(portal_sampling_pdf == 1.0f) {
/* Use uniform as a fallback if we can't sample the map. */
*pdf = 1.0f / M_4PI_F;
return sample_uniform_sphere(randu, randv);
}
else {
portal_sampling_pdf = 0.0f;
}
}
}
float3 D = background_map_sample(kg, randu, randv, pdf);
/* Use MIS if portals could be sampled as well. */
if(portal_sampling_pdf > 0.0f) {
float portal_pdf = background_portal_pdf(kg, P, D, -1, NULL);
*pdf = (portal_sampling_pdf * portal_pdf
+ (1.0f - portal_sampling_pdf) * (*pdf));
}
return D;
}
ccl_device float background_light_pdf(KernelGlobals *kg, float3 P, float3 direction)
{
/* Probability of sampling portals instead of the map. */
float portal_sampling_pdf = kernel_data.integrator.portal_pdf;
float portal_pdf = 0.0f, map_pdf = 0.0f;
if(portal_sampling_pdf > 0.0f) {
/* Evaluate PDF of sampling this direction by portal sampling. */
bool is_possible = false;
portal_pdf = background_portal_pdf(kg, P, direction, -1, &is_possible) * portal_sampling_pdf;
if(!is_possible) {
/* Portal sampling is not possible here because all portals point to the wrong side.
* If map sampling is possible, it would be used instead, otherwise fallback sampling is used. */
if(portal_sampling_pdf == 1.0f) {
return kernel_data.integrator.pdf_lights / M_4PI_F;
}
else {
/* Force map sampling. */
portal_sampling_pdf = 0.0f;
}
}
}
if(portal_sampling_pdf < 1.0f) {
/* Evaluate PDF of sampling this direction by map sampling. */
map_pdf = background_map_pdf(kg, direction) * (1.0f - portal_sampling_pdf);
}
return (portal_pdf + map_pdf) * kernel_data.integrator.pdf_lights;
}
#endif
/* 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);
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 D = 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, D) > 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;
ls->pdf = rect_light_sample(P, &ls->P,
axisu, 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 = D;
ls->D = normalize_len(ls->P - P, &ls->t);
ls->eval_fac = 0.25f*invarea;
if(is_round) {
ls->pdf *= lamp_light_pdf(kg, D, -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);
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 {
ls->pdf = rect_light_sample(P, &light_P, axisu, axisv, 0, 0, false);
}
ls->eval_fac = 0.25f*invarea;
}
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);
}
#ifdef __INSTANCING__
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;
}
#endif
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 */
randu = sqrtf(randu);
const float u = 1.0f - randu;
const float v = randv*randu;
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;
while(len > 0) {
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;
}
}
/* 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 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,
float randu,
float randv,
float time,
float3 P,
int bounce,
LightSample *ls)
{
/* 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);
}
else {
int 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 int light_select_num_samples(KernelGlobals *kg, int index)
{
return kernel_tex_fetch(__lights, index).samples;
}
CCL_NAMESPACE_END
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