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Fix T46760: Branched Path Tracing converges to different result than plain Path Tracing

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Multiple importance sampling for branched path tracing light samples needs to be
calculated separately per BSDF, not with Veach's one sample model.
This commit is contained in:
Stefan Werner
2015-11-20 17:44:19 +01:00
committed by Sergey Sharybin
parent 35cf545e3a
commit c8a041f489
2 changed files with 53 additions and 13 deletions
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20
intern/cycles/kernel/kernel_emission.h
View File

@@ -99,23 +99,23 @@ ccl_device_noinline bool direct_emission(KernelGlobals *kg, ShaderData *sd,
return false;
/* evaluate BSDF at shading point */
float bsdf_pdf;
#ifdef __VOLUME__
if(ccl_fetch(sd, prim) != PRIM_NONE)
shader_bsdf_eval(kg, sd, ls->D, eval, &bsdf_pdf);
else
shader_bsdf_eval(kg, sd, ls->D, eval, ls->pdf, ls->shader & SHADER_USE_MIS);
else {
float bsdf_pdf;
shader_volume_phase_eval(kg, sd, ls->D, eval, &bsdf_pdf);
if(ls->shader & SHADER_USE_MIS) {
/* Multiple importance sampling. */
float mis_weight = power_heuristic(ls->pdf, bsdf_pdf);
light_eval *= mis_weight;
}
}
#else
shader_bsdf_eval(kg, sd, ls->D, eval, &bsdf_pdf);
shader_bsdf_eval(kg, sd, ls->D, eval, ls->pdf, ls->shader & SHADER_USE_MIS);
#endif
if(ls->shader & SHADER_USE_MIS) {
/* multiple importance sampling */
float mis_weight = power_heuristic(ls->pdf, bsdf_pdf);
light_eval *= mis_weight;
}
bsdf_eval_mul(eval, light_eval/ls->pdf);
#ifdef __PASSES__

46
intern/cycles/kernel/kernel_shader.h
View File

@@ -516,12 +516,52 @@ ccl_device_inline void _shader_bsdf_multi_eval(KernelGlobals *kg, const ShaderDa
*pdf = (sum_sample_weight > 0.0f)? sum_pdf/sum_sample_weight: 0.0f;
}
ccl_device void shader_bsdf_eval(KernelGlobals *kg, ShaderData *sd,
const float3 omega_in, BsdfEval *eval, float *pdf)
#ifdef __BRANCHED_PATH__
ccl_device_inline void _shader_bsdf_multi_eval_branched(KernelGlobals *kg,
const ShaderData *sd,
const float3 omega_in,
BsdfEval *result_eval,
float light_pdf,
bool use_mis)
{
for(int i = 0; i < ccl_fetch(sd, num_closure); i++) {
const ShaderClosure *sc = ccl_fetch_array(sd, closure, i);
if(CLOSURE_IS_BSDF(sc->type)) {
float bsdf_pdf = 0.0f;
float3 eval = bsdf_eval(kg, sd, sc, omega_in, &bsdf_pdf);
if(bsdf_pdf != 0.0f) {
float mis_weight = use_mis? power_heuristic(light_pdf, bsdf_pdf): 1.0f;
bsdf_eval_accum(result_eval,
sc->type,
eval * sc->weight * mis_weight);
}
}
}
}
#endif
ccl_device void shader_bsdf_eval(KernelGlobals *kg,
ShaderData *sd,
const float3 omega_in,
BsdfEval *eval,
float light_pdf,
bool use_mis)
{
bsdf_eval_init(eval, NBUILTIN_CLOSURES, make_float3(0.0f, 0.0f, 0.0f), kernel_data.film.use_light_pass);
_shader_bsdf_multi_eval(kg, sd, omega_in, pdf, -1, eval, 0.0f, 0.0f);
#ifdef __BRANCHED_PATH__
if(kernel_data.integrator.branched)
_shader_bsdf_multi_eval_branched(kg, sd, omega_in, eval, light_pdf, use_mis);
else
#endif
{
float pdf;
_shader_bsdf_multi_eval(kg, sd, omega_in, &pdf, -1, eval, 0.0f, 0.0f);
if(use_mis) {
float weight = power_heuristic(light_pdf, pdf);
bsdf_eval_mul(eval, make_float3(weight, weight, weight));
}
}
}
ccl_device int shader_bsdf_sample(KernelGlobals *kg, const ShaderData *sd,