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Fix T40408: world MIS + equiangular sampling giving unnecessary noise. 

It's actually not possible to do equiangular sampling for distant lights, now
it reverts to distance sampling in this case.
This commit is contained in:
Brecht Van Lommel 2014-05-29 13:20:42 +02:00
parent 9c9fc626b7
commit 9e61dcc6b8
Notes: blender-bot 2023-02-14 11:21:40 +01:00 
Referenced by issue #40408, World Multiple importance sample + Equi-angular sampling gives noise and weirdness in volumes in 2.71 testbuild
1 changed files with 31 additions and 21 deletions
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52
intern/cycles/kernel/kernel_volume.h
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@ -226,7 +226,7 @@ ccl_device float kernel_volume_equiangular_pdf(Ray *ray, float3 light_P, float s
return pdf;
}
ccl_device bool kernel_volume_equiangular_light_position(KernelGlobals *kg, PathState *state, Ray *ray, RNG *rng, float3 *light_P)
ccl_device bool kernel_volume_equiangular_light_position(KernelGlobals *kg, PathState *state, Ray *ray, RNG *rng, float3 *light_P, bool *distant)
{
/* light RNGs */
float light_t = path_state_rng_1D(kg, rng, state, PRNG_LIGHT);
@ -240,19 +240,11 @@ ccl_device bool kernel_volume_equiangular_light_position(KernelGlobals *kg, Path
return false;
*light_P = ls.P;
*distant = ls.t == FLT_MAX;
return true;
}
ccl_device float kernel_volume_decoupled_equiangular_pdf(KernelGlobals *kg, PathState *state, Ray *ray, RNG *rng, float sample_t)
{
float3 light_P;
if(!kernel_volume_equiangular_light_position(kg, state, ray, rng, &light_P))
return 0.0f;
return kernel_volume_equiangular_pdf(ray, light_P, sample_t);
}
/* Distance sampling */
ccl_device float kernel_volume_distance_sample(float max_t, float3 sigma_t, int channel, float xi, float3 *transmittance, float3 *pdf)
@ -357,12 +349,20 @@ ccl_device VolumeIntegrateResult kernel_volume_integrate_homogeneous(KernelGloba
/* equiangular sampling */
float3 light_P;
float equi_pdf;
if(!kernel_volume_equiangular_light_position(kg, state, ray, rng, &light_P))
bool light_distant;
if(!kernel_volume_equiangular_light_position(kg, state, ray, rng, &light_P, &light_distant))
return VOLUME_PATH_MISSED;
sample_t = kernel_volume_equiangular_sample(ray, light_P, xi, &equi_pdf);
transmittance = volume_color_transmittance(sigma_t, sample_t);
pdf = make_float3(equi_pdf, equi_pdf, equi_pdf);
if(light_distant) {
/* distant light, revert to distance sampling because position is infinitely far away */
sample_t = kernel_volume_distance_sample(ray->t, sigma_t, channel, xi, &transmittance, &pdf);
}
else {
sample_t = kernel_volume_equiangular_sample(ray, light_P, xi, &equi_pdf);
transmittance = volume_color_transmittance(sigma_t, sample_t);
pdf = make_float3(equi_pdf, equi_pdf, equi_pdf);
}
}
/* modifiy pdf for hit/miss decision */
@ -720,8 +720,23 @@ ccl_device VolumeIntegrateResult kernel_volume_decoupled_scatter(
float3 transmittance;
float pdf, sample_t;
/* pick position on light for equiangular */
bool equiangular = (kernel_data.integrator.volume_homogeneous_sampling != 0 && kernel_data.integrator.num_all_lights);
float3 light_P;
if(equiangular) {
bool light_distant;
if(!kernel_volume_equiangular_light_position(kg, state, ray, rng, &light_P, &light_distant))
return VOLUME_PATH_MISSED;
/* distant light, revert to distance sampling because position is infinitely far away */
if(light_distant)
equiangular = false;
}
/* distance sampling */
if(kernel_data.integrator.volume_homogeneous_sampling == 0 || !kernel_data.integrator.num_all_lights) {
if(!equiangular) {
/* find step in cdf */
step = segment->steps;
@ -762,11 +777,6 @@ ccl_device VolumeIntegrateResult kernel_volume_decoupled_scatter(
}
/* equi-angular sampling */
else {
/* pick position on light */
float3 light_P;
if(!kernel_volume_equiangular_light_position(kg, state, ray, rng, &light_P))
return VOLUME_PATH_MISSED;
/* sample distance */
sample_t = kernel_volume_equiangular_sample(ray, light_P, xi, &pdf);