[Bf-blender-cvs] [cd6c9e9e5f4] master: Cycles: improve sample stratification on area lights for path tracing.
Brecht Van Lommel
noreply at git.blender.org
Tue Sep 12 13:01:22 CEST 2017
Commit: cd6c9e9e5f4726ab0b0b2c58249f98dab5c5d267
Author: Brecht Van Lommel
Date: Fri Sep 8 01:42:14 2017 +0200
Branches: master
https://developer.blender.org/rBcd6c9e9e5f4726ab0b0b2c58249f98dab5c5d267
Cycles: improve sample stratification on area lights for path tracing.
Previously we used a 1D sequence to select a light, and another 2D sequence
to sample a point on the light. For multiple lights this meant each light
would get a random subset of a 2D stratified sequence, which is not
guaranteed to be stratified anymore.
Now we use only a 2D sequence, split into segments along the X axis, one for
each light. The samples that fall within a segment then each are a stratified
sequence, at least in the limit. So for example for two lights, we split up
the unit square into two segments [0,0.5[ x [0,1[ and [0.5,1[ x [0,1[.
This doesn't make much difference in most scenes, mainly helps if you have a
few large area lights or some types of HDR backgrounds.
===================================================================
M intern/cycles/kernel/kernel_light.h
M intern/cycles/kernel/kernel_path_surface.h
M intern/cycles/kernel/kernel_path_volume.h
M intern/cycles/kernel/kernel_types.h
M intern/cycles/kernel/split/kernel_direct_lighting.h
===================================================================
diff --git a/intern/cycles/kernel/kernel_light.h b/intern/cycles/kernel/kernel_light.h
index 59db6cbd430..9f1a48f9bba 100644
--- a/intern/cycles/kernel/kernel_light.h
+++ b/intern/cycles/kernel/kernel_light.h
@@ -1013,20 +1013,21 @@ ccl_device_forceinline void triangle_light_sample(KernelGlobals *kg, int prim, i
/* Light Distribution */
-ccl_device int light_distribution_sample(KernelGlobals *kg, float randt)
+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
+ /* 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
- * OSL shaders. */
+ * 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(randt < kernel_tex_fetch(__light_distribution, middle).x) {
+ if(r < kernel_tex_fetch(__light_distribution, middle).x) {
len = half_len;
}
else {
@@ -1035,9 +1036,17 @@ ccl_device int light_distribution_sample(KernelGlobals *kg, float randt)
}
}
- /* clamping should not be needed but float rounding errors seem to
- * make this fail on rare occasions */
- return clamp(first-1, 0, kernel_data.integrator.num_distribution-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).x;
+ float distr_max = kernel_tex_fetch(__light_distribution, index+1).x;
+ *randu = (r - distr_min)/(distr_max - distr_min);
+
+ return index;
}
/* Generic Light */
@@ -1049,7 +1058,6 @@ ccl_device bool light_select_reached_max_bounces(KernelGlobals *kg, int index, i
}
ccl_device_noinline bool light_sample(KernelGlobals *kg,
- float randt,
float randu,
float randv,
float time,
@@ -1058,7 +1066,7 @@ ccl_device_noinline bool light_sample(KernelGlobals *kg,
LightSample *ls)
{
/* sample index */
- int index = light_distribution_sample(kg, randt);
+ int index = light_distribution_sample(kg, &randu);
/* fetch light data */
float4 l = kernel_tex_fetch(__light_distribution, index);
diff --git a/intern/cycles/kernel/kernel_path_surface.h b/intern/cycles/kernel/kernel_path_surface.h
index 6c3a444e48a..e798fcc6a2c 100644
--- a/intern/cycles/kernel/kernel_path_surface.h
+++ b/intern/cycles/kernel/kernel_path_surface.h
@@ -85,17 +85,16 @@ ccl_device_noinline void kernel_branched_path_surface_connect_light(
float num_samples_inv = num_samples_adjust/num_samples;
for(int j = 0; j < num_samples; j++) {
- float light_t = path_branched_rng_1D(kg, state->rng_hash, state, j, num_samples, PRNG_LIGHT);
float light_u, light_v;
path_branched_rng_2D(kg, state->rng_hash, state, j, num_samples, PRNG_LIGHT_U, &light_u, &light_v);
float terminate = path_branched_rng_light_termination(kg, state->rng_hash, state, j, num_samples);
/* only sample triangle lights */
if(kernel_data.integrator.num_all_lights)
- light_t = 0.5f*light_t;
+ light_u = 0.5f*light_u;
LightSample ls;
- if(light_sample(kg, light_t, light_u, light_v, sd->time, sd->P, state->bounce, &ls)) {
+ if(light_sample(kg, light_u, light_v, sd->time, sd->P, state->bounce, &ls)) {
/* Same as above, probability needs to be corrected since the sampling was forced to select a mesh light. */
if(kernel_data.integrator.num_all_lights)
ls.pdf *= 2.0f;
@@ -118,13 +117,12 @@ ccl_device_noinline void kernel_branched_path_surface_connect_light(
}
else {
/* sample one light at random */
- float light_t = path_state_rng_1D(kg, state, PRNG_LIGHT);
float light_u, light_v;
path_state_rng_2D(kg, state, PRNG_LIGHT_U, &light_u, &light_v);
float terminate = path_state_rng_light_termination(kg, state);
LightSample ls;
- if(light_sample(kg, light_t, light_u, light_v, sd->time, sd->P, state->bounce, &ls)) {
+ if(light_sample(kg, light_u, light_v, sd->time, sd->P, state->bounce, &ls)) {
/* sample random light */
if(direct_emission(kg, sd, emission_sd, &ls, state, &light_ray, &L_light, &is_lamp, terminate)) {
/* trace shadow ray */
@@ -238,7 +236,6 @@ ccl_device_inline void kernel_path_surface_connect_light(KernelGlobals *kg,
#endif
/* sample illumination from lights to find path contribution */
- float light_t = path_state_rng_1D(kg, state, PRNG_LIGHT);
float light_u, light_v;
path_state_rng_2D(kg, state, PRNG_LIGHT_U, &light_u, &light_v);
@@ -251,7 +248,7 @@ ccl_device_inline void kernel_path_surface_connect_light(KernelGlobals *kg,
#endif
LightSample ls;
- if(light_sample(kg, light_t, light_u, light_v, sd->time, sd->P, state->bounce, &ls)) {
+ if(light_sample(kg, light_u, light_v, sd->time, sd->P, state->bounce, &ls)) {
float terminate = path_state_rng_light_termination(kg, state);
if(direct_emission(kg, sd, emission_sd, &ls, state, &light_ray, &L_light, &is_lamp, terminate)) {
/* trace shadow ray */
diff --git a/intern/cycles/kernel/kernel_path_volume.h b/intern/cycles/kernel/kernel_path_volume.h
index c9c7f447c42..fb6b8d56a38 100644
--- a/intern/cycles/kernel/kernel_path_volume.h
+++ b/intern/cycles/kernel/kernel_path_volume.h
@@ -31,7 +31,6 @@ ccl_device_inline void kernel_path_volume_connect_light(
return;
/* sample illumination from lights to find path contribution */
- float light_t = path_state_rng_1D(kg, state, PRNG_LIGHT);
float light_u, light_v;
path_state_rng_2D(kg, state, PRNG_LIGHT_U, &light_u, &light_v);
@@ -45,7 +44,7 @@ ccl_device_inline void kernel_path_volume_connect_light(
light_ray.time = sd->time;
# endif
- if(light_sample(kg, light_t, light_u, light_v, sd->time, sd->P, state->bounce, &ls))
+ if(light_sample(kg, light_u, light_v, sd->time, sd->P, state->bounce, &ls))
{
float terminate = path_state_rng_light_termination(kg, state);
if(direct_emission(kg, sd, emission_sd, &ls, state, &light_ray, &L_light, &is_lamp, terminate)) {
@@ -195,16 +194,15 @@ ccl_device void kernel_branched_path_volume_connect_light(
for(int j = 0; j < num_samples; j++) {
/* sample random position on random triangle */
- float light_t = path_branched_rng_1D_for_decision(kg, state->rng_hash, state, j, num_samples, PRNG_LIGHT);
float light_u, light_v;
path_branched_rng_2D(kg, state->rng_hash, state, j, num_samples, PRNG_LIGHT_U, &light_u, &light_v);
/* only sample triangle lights */
if(kernel_data.integrator.num_all_lights)
- light_t = 0.5f*light_t;
+ light_u = 0.5f*light_u;
LightSample ls;
- light_sample(kg, light_t, light_u, light_v, sd->time, ray->P, state->bounce, &ls);
+ light_sample(kg, light_u, light_v, sd->time, ray->P, state->bounce, &ls);
float3 tp = throughput;
@@ -219,7 +217,7 @@ ccl_device void kernel_branched_path_volume_connect_light(
kernel_assert(result == VOLUME_PATH_SCATTERED);
/* todo: split up light_sample so we don't have to call it again with new position */
- if(light_sample(kg, light_t, light_u, light_v, sd->time, sd->P, state->bounce, &ls)) {
+ if(light_sample(kg, light_u, light_v, sd->time, sd->P, state->bounce, &ls)) {
if(kernel_data.integrator.num_all_lights)
ls.pdf *= 2.0f;
@@ -239,12 +237,11 @@ ccl_device void kernel_branched_path_volume_connect_light(
}
else {
/* sample random position on random light */
- float light_t = path_state_rng_1D(kg, state, PRNG_LIGHT);
float light_u, light_v;
path_state_rng_2D(kg, state, PRNG_LIGHT_U, &light_u, &light_v);
LightSample ls;
- light_sample(kg, light_t, light_u, light_v, sd->time, ray->P, state->bounce, &ls);
+ light_sample(kg, light_u, light_v, sd->time, ray->P, state->bounce, &ls);
float3 tp = throughput;
@@ -259,7 +256,7 @@ ccl_device void kernel_branched_path_volume_connect_light(
kernel_assert(result == VOLUME_PATH_SCATTERED);
/* todo: split up light_sample so we don't have to call it again with new position */
- if(light_sample(kg, light_t, light_u, light_v, sd->time, sd->P, state->bounce, &ls)) {
+ if(light_sample(kg, light_u, light_v, sd->time, sd->P, state->bounce, &ls)) {
/* sample random light */
float terminate = path_state_rng_light_termination(kg, state);
if(direct_emission(kg, sd, emission_sd, &ls, state, &light_ray, &L_light, &is_lamp, terminate)) {
diff --git a/intern/cycles/kernel/kernel_types.h b/intern/cycles/kernel/kernel_types.h
index 8f65c00491c..2c7e9b82feb 100644
--- a/intern/cycles/kernel/kernel_types.h
+++ b/intern/cycles/kernel/kernel_types.h
@@ -292,7 +292,7 @@ enum PathTraceDimension {
PRNG_BSDF_U = 0,
PRNG_BSDF_V = 1,
PRNG_BSDF = 2,
- PRNG_LIGHT = 3,
+ PRNG_UNUSED3 = 3,
PRNG_LIGHT_U = 4,
PRNG_LIGHT_V = 5,
PRNG_LIGHT_TERMINATE = 6,
diff --git a/intern/cycles/kernel/split/kernel_direct_lighting.h b/intern/cycles/kernel/split/kernel_direct_lighting.h
index 8e3f7555550..5009828df92 100644
--- a/intern/cycles/kernel/split/kernel_direct_lighting.h
+++ b/intern/cycles/kernel/split/kernel_direct_lighting.h
@@ -81,14 +81,13 @@ ccl_device void kernel_direct_lighting(KernelGlobals *kg,
if(flag) {
/* Sample illumination from lights to find path contribution. */
- float light_t = path_state_rng_1D(kg, state, PRNG_LIGHT);
float light_u, light_v;
path_state_rng_2D(kg, state, PRNG_LIGHT_U, &light_u, &light_v);
float terminate = path_state_rng_light_termination(kg, state);
LightSample ls;
if(light_sample(kg,
- light_t, light_u, light_v,
+ light_u, light_v,
sd->time,
sd->P,
st
@@ Diff output truncated at 10240 characters. @@
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