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Cycles: slightly improve BSDF sample stratification for path tracing.

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Similar to what we did for area lights previously, this should help
preserve stratification when using multiple BSDFs in theory. Improvements
are not easily noticeable in practice though, because the number of BSDFs
is usually low. Still nice to eliminate one sampling dimension.
This commit is contained in:
Brecht Van Lommel
2017-09-14 22:56:32 +02:00
parent b3afc8917c
commit 095a01a73a
13 changed files with 79 additions and 88 deletions
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21
intern/cycles/kernel/kernel_path.h
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@@ -210,7 +210,7 @@ ccl_device_forceinline VolumeIntegrateResult kernel_path_volume(
/* indirect sample. if we use distance sampling and take just
* one sample for direct and indirect light, we could share
* this computation, but makes code a bit complex */
float rphase = path_state_rng_1D(kg, state, PRNG_PHASE);
float rphase = path_state_rng_1D(kg, state, PRNG_PHASE_CHANNEL);
float rscatter = path_state_rng_1D(kg, state, PRNG_SCATTER_DISTANCE);
result = kernel_volume_decoupled_scatter(kg,
@@ -434,8 +434,7 @@ ccl_device void kernel_path_indirect(KernelGlobals *kg,
sd,
&isect,
ray);
float rbsdf = path_state_rng_1D(kg, state, PRNG_BSDF);
shader_eval_surface(kg, sd, state, rbsdf, state->flag);
shader_eval_surface(kg, sd, state, state->flag);
#ifdef __BRANCHED_PATH__
shader_merge_closures(sd);
#endif /* __BRANCHED_PATH__ */
@@ -483,17 +482,18 @@ ccl_device void kernel_path_indirect(KernelGlobals *kg,
/* bssrdf scatter to a different location on the same object, replacing
* the closures with a diffuse BSDF */
if(sd->flag & SD_BSSRDF) {
const ShaderClosure *sc = shader_bssrdf_pick(sd, &throughput);
float bssrdf_u, bssrdf_v;
path_state_rng_2D(kg,
state,
PRNG_BSDF_U,
&bssrdf_u, &bssrdf_v);
const ShaderClosure *sc = shader_bssrdf_pick(sd, &throughput, &bssrdf_u);
/* do bssrdf scatter step if we picked a bssrdf closure */
if(sc) {
uint lcg_state = lcg_state_init(state, 0x68bc21eb);
float bssrdf_u, bssrdf_v;
path_state_rng_2D(kg,
state,
PRNG_BSDF_U,
&bssrdf_u, &bssrdf_v);
subsurface_scatter_step(kg,
sd,
state,
@@ -587,8 +587,7 @@ ccl_device_forceinline void kernel_path_integrate(
/* Setup and evaluate shader. */
shader_setup_from_ray(kg, &sd, &isect, ray);
float rbsdf = path_state_rng_1D(kg, state, PRNG_BSDF);
shader_eval_surface(kg, &sd, state, rbsdf, state->flag);
shader_eval_surface(kg, &sd, state, state->flag);
/* Apply shadow catcher, holdout, emission. */
if(!kernel_path_shader_apply(kg,