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23c276832b
blender/intern/cycles/kernel/closure/bsdf.h
Lukas Stockner 23c276832b Cycles: Add multi-scattering, energy-conserving GGX as an option to the Glossy, Anisotropic and Glass BSDFs 
This commit adds a new distribution to the Glossy, Anisotropic and Glass BSDFs that implements the
multiple-scattering microfacet model described in the paper "Multiple-Scattering Microfacet BSDFs with the Smith Model".

Essentially, the improvement is that unlike classical GGX, which only models single scattering and assumes
the contribution of multiple bounces to be zero, this new model performs a random walk on the microsurface until
the ray leaves it again, which ensures perfect energy conservation.

In practise, this means that the "darkening problem" - GGX materials becoming darker with increasing
roughness - is solved in a physically correct and efficient way.

The downside of this model is that it has no (known) analytic expression for evalation. However, it can be
evaluated stochastically, and although the correct PDF isn't known either, the properties of MIS and the
balance heuristic guarantee an unbiased result at the cost of slightly higher noise.

Reviewers: dingto, #cycles, brecht

Reviewed By: dingto, #cycles, brecht

Subscribers: bliblubli, ace_dragon, gregzaal, brecht, harvester, dingto, marcog, swerner, jtheninja, Blendify, nutel

Differential Revision: https://developer.blender.org/D2002
2016-06-23 22:57:26 +02:00

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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.
*/
#include "../closure/bsdf_ashikhmin_velvet.h"
#include "../closure/bsdf_diffuse.h"
#include "../closure/bsdf_oren_nayar.h"
#include "../closure/bsdf_phong_ramp.h"
#include "../closure/bsdf_diffuse_ramp.h"
#include "../closure/bsdf_microfacet.h"
#include "../closure/bsdf_microfacet_multi.h"
#include "../closure/bsdf_reflection.h"
#include "../closure/bsdf_refraction.h"
#include "../closure/bsdf_transparent.h"
#include "../closure/bsdf_ashikhmin_shirley.h"
#include "../closure/bsdf_toon.h"
#include "../closure/bsdf_hair.h"
#ifdef __SUBSURFACE__
# include "../closure/bssrdf.h"
#endif
#ifdef __VOLUME__
# include "../closure/volume.h"
#endif
CCL_NAMESPACE_BEGIN
ccl_device int bsdf_sample(KernelGlobals *kg, ShaderData *sd, const ShaderClosure *sc, float randu, float randv, float3 *eval, float3 *omega_in, differential3 *domega_in, float *pdf)
{
int label;
#ifdef __OSL__
if(kg->osl && sc->prim)
return OSLShader::bsdf_sample(sd, sc, randu, randv, *eval, *omega_in, *domega_in, *pdf);
#endif
switch(sc->type) {
case CLOSURE_BSDF_DIFFUSE_ID:
case CLOSURE_BSDF_BSSRDF_ID:
label = bsdf_diffuse_sample(sc, ccl_fetch(sd, Ng), ccl_fetch(sd, I), ccl_fetch(sd, dI).dx, ccl_fetch(sd, dI).dy, randu, randv,
eval, omega_in, &domega_in->dx, &domega_in->dy, pdf);
break;
#ifdef __SVM__
case CLOSURE_BSDF_OREN_NAYAR_ID:
label = bsdf_oren_nayar_sample(sc, ccl_fetch(sd, Ng), ccl_fetch(sd, I), ccl_fetch(sd, dI).dx, ccl_fetch(sd, dI).dy, randu, randv,
eval, omega_in, &domega_in->dx, &domega_in->dy, pdf);
break;
/*case CLOSURE_BSDF_PHONG_RAMP_ID:
label = bsdf_phong_ramp_sample(sc, ccl_fetch(sd, Ng), ccl_fetch(sd, I), ccl_fetch(sd, dI).dx, ccl_fetch(sd, dI).dy, randu, randv,
eval, omega_in, &domega_in->dx, &domega_in->dy, pdf);
break;
case CLOSURE_BSDF_DIFFUSE_RAMP_ID:
label = bsdf_diffuse_ramp_sample(sc, ccl_fetch(sd, Ng), ccl_fetch(sd, I), ccl_fetch(sd, dI).dx, ccl_fetch(sd, dI).dy, randu, randv,
eval, omega_in, &domega_in->dx, &domega_in->dy, pdf);
break;*/
case CLOSURE_BSDF_TRANSLUCENT_ID:
label = bsdf_translucent_sample(sc, ccl_fetch(sd, Ng), ccl_fetch(sd, I), ccl_fetch(sd, dI).dx, ccl_fetch(sd, dI).dy, randu, randv,
eval, omega_in, &domega_in->dx, &domega_in->dy, pdf);
break;
case CLOSURE_BSDF_REFLECTION_ID:
label = bsdf_reflection_sample(sc, ccl_fetch(sd, Ng), ccl_fetch(sd, I), ccl_fetch(sd, dI).dx, ccl_fetch(sd, dI).dy, randu, randv,
eval, omega_in, &domega_in->dx, &domega_in->dy, pdf);
break;
case CLOSURE_BSDF_REFRACTION_ID:
label = bsdf_refraction_sample(sc, ccl_fetch(sd, Ng), ccl_fetch(sd, I), ccl_fetch(sd, dI).dx, ccl_fetch(sd, dI).dy, randu, randv,
eval, omega_in, &domega_in->dx, &domega_in->dy, pdf);
break;
case CLOSURE_BSDF_TRANSPARENT_ID:
label = bsdf_transparent_sample(sc, ccl_fetch(sd, Ng), ccl_fetch(sd, I), ccl_fetch(sd, dI).dx, ccl_fetch(sd, dI).dy, randu, randv,
eval, omega_in, &domega_in->dx, &domega_in->dy, pdf);
break;
case CLOSURE_BSDF_MICROFACET_GGX_ID:
case CLOSURE_BSDF_MICROFACET_GGX_ANISO_ID:
case CLOSURE_BSDF_MICROFACET_GGX_REFRACTION_ID:
label = bsdf_microfacet_ggx_sample(kg, sc, ccl_fetch(sd, Ng), ccl_fetch(sd, I), ccl_fetch(sd, dI).dx, ccl_fetch(sd, dI).dy, randu, randv,
eval, omega_in, &domega_in->dx, &domega_in->dy, pdf);
break;
case CLOSURE_BSDF_MICROFACET_MULTI_GGX_ID:
label = bsdf_microfacet_multi_ggx_sample(kg, sc, ccl_fetch(sd, Ng), ccl_fetch(sd, I), ccl_fetch(sd, dI).dx, ccl_fetch(sd, dI).dy, randu, randv,
eval, omega_in, &domega_in->dx, &domega_in->dy, pdf, &ccl_fetch(sd, lcg_state));
break;
case CLOSURE_BSDF_MICROFACET_MULTI_GGX_GLASS_ID:
label = bsdf_microfacet_multi_ggx_glass_sample(kg, sc, ccl_fetch(sd, Ng), ccl_fetch(sd, I), ccl_fetch(sd, dI).dx, ccl_fetch(sd, dI).dy, randu, randv,
eval, omega_in, &domega_in->dx, &domega_in->dy, pdf, &ccl_fetch(sd, lcg_state));
break;
case CLOSURE_BSDF_MICROFACET_BECKMANN_ID:
case CLOSURE_BSDF_MICROFACET_BECKMANN_ANISO_ID:
case CLOSURE_BSDF_MICROFACET_BECKMANN_REFRACTION_ID:
label = bsdf_microfacet_beckmann_sample(kg, sc, ccl_fetch(sd, Ng), ccl_fetch(sd, I), ccl_fetch(sd, dI).dx, ccl_fetch(sd, dI).dy, randu, randv,
eval, omega_in, &domega_in->dx, &domega_in->dy, pdf);
break;
case CLOSURE_BSDF_ASHIKHMIN_SHIRLEY_ID:
case CLOSURE_BSDF_ASHIKHMIN_SHIRLEY_ANISO_ID:
label = bsdf_ashikhmin_shirley_sample(sc, ccl_fetch(sd, Ng), ccl_fetch(sd, I), ccl_fetch(sd, dI).dx, ccl_fetch(sd, dI).dy, randu, randv,
eval, omega_in, &domega_in->dx, &domega_in->dy, pdf);
break;
case CLOSURE_BSDF_ASHIKHMIN_VELVET_ID:
label = bsdf_ashikhmin_velvet_sample(sc, ccl_fetch(sd, Ng), ccl_fetch(sd, I), ccl_fetch(sd, dI).dx, ccl_fetch(sd, dI).dy, randu, randv,
eval, omega_in, &domega_in->dx, &domega_in->dy, pdf);
break;
case CLOSURE_BSDF_DIFFUSE_TOON_ID:
label = bsdf_diffuse_toon_sample(sc, ccl_fetch(sd, Ng), ccl_fetch(sd, I), ccl_fetch(sd, dI).dx, ccl_fetch(sd, dI).dy, randu, randv,
eval, omega_in, &domega_in->dx, &domega_in->dy, pdf);
break;
case CLOSURE_BSDF_GLOSSY_TOON_ID:
label = bsdf_glossy_toon_sample(sc, ccl_fetch(sd, Ng), ccl_fetch(sd, I), ccl_fetch(sd, dI).dx, ccl_fetch(sd, dI).dy, randu, randv,
eval, omega_in, &domega_in->dx, &domega_in->dy, pdf);
break;
case CLOSURE_BSDF_HAIR_REFLECTION_ID:
label = bsdf_hair_reflection_sample(sc, ccl_fetch(sd, Ng), ccl_fetch(sd, I), ccl_fetch(sd, dI).dx, ccl_fetch(sd, dI).dy, randu, randv,
eval, omega_in, &domega_in->dx, &domega_in->dy, pdf);
break;
case CLOSURE_BSDF_HAIR_TRANSMISSION_ID:
label = bsdf_hair_transmission_sample(sc, ccl_fetch(sd, Ng), ccl_fetch(sd, I), ccl_fetch(sd, dI).dx, ccl_fetch(sd, dI).dy, randu, randv,
eval, omega_in, &domega_in->dx, &domega_in->dy, pdf);
break;
#endif
#ifdef __VOLUME__
case CLOSURE_VOLUME_HENYEY_GREENSTEIN_ID:
label = volume_henyey_greenstein_sample(sc, ccl_fetch(sd, I), ccl_fetch(sd, dI).dx, ccl_fetch(sd, dI).dy, randu, randv, eval, omega_in, &domega_in->dx, &domega_in->dy, pdf);
break;
#endif
default:
label = LABEL_NONE;
break;
}
return label;
}
ccl_device float3 bsdf_eval(KernelGlobals *kg, ShaderData *sd, const ShaderClosure *sc, const float3 omega_in, float *pdf)
{
float3 eval;
#ifdef __OSL__
if(kg->osl && sc->prim)
return OSLShader::bsdf_eval(sd, sc, omega_in, *pdf);
#endif
if(dot(ccl_fetch(sd, Ng), omega_in) >= 0.0f) {
switch(sc->type) {
case CLOSURE_BSDF_DIFFUSE_ID:
case CLOSURE_BSDF_BSSRDF_ID:
eval = bsdf_diffuse_eval_reflect(sc, ccl_fetch(sd, I), omega_in, pdf);
break;
#ifdef __SVM__
case CLOSURE_BSDF_OREN_NAYAR_ID:
eval = bsdf_oren_nayar_eval_reflect(sc, ccl_fetch(sd, I), omega_in, pdf);
break;
/*case CLOSURE_BSDF_PHONG_RAMP_ID:
eval = bsdf_phong_ramp_eval_reflect(sc, ccl_fetch(sd, I), omega_in, pdf);
break;
case CLOSURE_BSDF_DIFFUSE_RAMP_ID:
eval = bsdf_diffuse_ramp_eval_reflect(sc, ccl_fetch(sd, I), omega_in, pdf);
break;*/
case CLOSURE_BSDF_TRANSLUCENT_ID:
eval = bsdf_translucent_eval_reflect(sc, ccl_fetch(sd, I), omega_in, pdf);
break;
case CLOSURE_BSDF_REFLECTION_ID:
eval = bsdf_reflection_eval_reflect(sc, ccl_fetch(sd, I), omega_in, pdf);
break;
case CLOSURE_BSDF_REFRACTION_ID:
eval = bsdf_refraction_eval_reflect(sc, ccl_fetch(sd, I), omega_in, pdf);
break;
case CLOSURE_BSDF_TRANSPARENT_ID:
eval = bsdf_transparent_eval_reflect(sc, ccl_fetch(sd, I), omega_in, pdf);
break;
case CLOSURE_BSDF_MICROFACET_GGX_ID:
case CLOSURE_BSDF_MICROFACET_GGX_ANISO_ID:
case CLOSURE_BSDF_MICROFACET_GGX_REFRACTION_ID:
eval = bsdf_microfacet_ggx_eval_reflect(sc, ccl_fetch(sd, I), omega_in, pdf);
break;
case CLOSURE_BSDF_MICROFACET_MULTI_GGX_ID:
eval = bsdf_microfacet_multi_ggx_eval_reflect(sc, ccl_fetch(sd, I), omega_in, pdf, &ccl_fetch(sd, lcg_state));
break;
case CLOSURE_BSDF_MICROFACET_MULTI_GGX_GLASS_ID:
eval = bsdf_microfacet_multi_ggx_glass_eval_reflect(sc, ccl_fetch(sd, I), omega_in, pdf, &ccl_fetch(sd, lcg_state));
break;
case CLOSURE_BSDF_MICROFACET_BECKMANN_ID:
case CLOSURE_BSDF_MICROFACET_BECKMANN_ANISO_ID:
case CLOSURE_BSDF_MICROFACET_BECKMANN_REFRACTION_ID:
eval = bsdf_microfacet_beckmann_eval_reflect(sc, ccl_fetch(sd, I), omega_in, pdf);
break;
case CLOSURE_BSDF_ASHIKHMIN_SHIRLEY_ID:
case CLOSURE_BSDF_ASHIKHMIN_SHIRLEY_ANISO_ID:
eval = bsdf_ashikhmin_shirley_eval_reflect(sc, ccl_fetch(sd, I), omega_in, pdf);
break;
case CLOSURE_BSDF_ASHIKHMIN_VELVET_ID:
eval = bsdf_ashikhmin_velvet_eval_reflect(sc, ccl_fetch(sd, I), omega_in, pdf);
break;
case CLOSURE_BSDF_DIFFUSE_TOON_ID:
eval = bsdf_diffuse_toon_eval_reflect(sc, ccl_fetch(sd, I), omega_in, pdf);
break;
case CLOSURE_BSDF_GLOSSY_TOON_ID:
eval = bsdf_glossy_toon_eval_reflect(sc, ccl_fetch(sd, I), omega_in, pdf);
break;
case CLOSURE_BSDF_HAIR_REFLECTION_ID:
eval = bsdf_hair_reflection_eval_reflect(sc, ccl_fetch(sd, I), omega_in, pdf);
break;
case CLOSURE_BSDF_HAIR_TRANSMISSION_ID:
eval = bsdf_hair_transmission_eval_reflect(sc, ccl_fetch(sd, I), omega_in, pdf);
break;
#endif
#ifdef __VOLUME__
case CLOSURE_VOLUME_HENYEY_GREENSTEIN_ID:
eval = volume_henyey_greenstein_eval_phase(sc, ccl_fetch(sd, I), omega_in, pdf);
break;
#endif
default:
eval = make_float3(0.0f, 0.0f, 0.0f);
break;
}
}
else {
switch(sc->type) {
case CLOSURE_BSDF_DIFFUSE_ID:
case CLOSURE_BSDF_BSSRDF_ID:
eval = bsdf_diffuse_eval_transmit(sc, ccl_fetch(sd, I), omega_in, pdf);
break;
#ifdef __SVM__
case CLOSURE_BSDF_OREN_NAYAR_ID:
eval = bsdf_oren_nayar_eval_transmit(sc, ccl_fetch(sd, I), omega_in, pdf);
break;
case CLOSURE_BSDF_TRANSLUCENT_ID:
eval = bsdf_translucent_eval_transmit(sc, ccl_fetch(sd, I), omega_in, pdf);
break;
case CLOSURE_BSDF_REFLECTION_ID:
eval = bsdf_reflection_eval_transmit(sc, ccl_fetch(sd, I), omega_in, pdf);
break;
case CLOSURE_BSDF_REFRACTION_ID:
eval = bsdf_refraction_eval_transmit(sc, ccl_fetch(sd, I), omega_in, pdf);
break;
case CLOSURE_BSDF_TRANSPARENT_ID:
eval = bsdf_transparent_eval_transmit(sc, ccl_fetch(sd, I), omega_in, pdf);
break;
case CLOSURE_BSDF_MICROFACET_GGX_ID:
case CLOSURE_BSDF_MICROFACET_GGX_ANISO_ID:
case CLOSURE_BSDF_MICROFACET_GGX_REFRACTION_ID:
eval = bsdf_microfacet_ggx_eval_transmit(sc, ccl_fetch(sd, I), omega_in, pdf);
break;
case CLOSURE_BSDF_MICROFACET_MULTI_GGX_ID:
eval = bsdf_microfacet_multi_ggx_eval_transmit(sc, ccl_fetch(sd, I), omega_in, pdf, &ccl_fetch(sd, lcg_state));
break;
case CLOSURE_BSDF_MICROFACET_MULTI_GGX_GLASS_ID:
eval = bsdf_microfacet_multi_ggx_glass_eval_transmit(sc, ccl_fetch(sd, I), omega_in, pdf, &ccl_fetch(sd, lcg_state));
break;
case CLOSURE_BSDF_MICROFACET_BECKMANN_ID:
case CLOSURE_BSDF_MICROFACET_BECKMANN_ANISO_ID:
case CLOSURE_BSDF_MICROFACET_BECKMANN_REFRACTION_ID:
eval = bsdf_microfacet_beckmann_eval_transmit(sc, ccl_fetch(sd, I), omega_in, pdf);
break;
case CLOSURE_BSDF_ASHIKHMIN_SHIRLEY_ID:
case CLOSURE_BSDF_ASHIKHMIN_SHIRLEY_ANISO_ID:
eval = bsdf_ashikhmin_shirley_eval_transmit(sc, ccl_fetch(sd, I), omega_in, pdf);
break;
case CLOSURE_BSDF_ASHIKHMIN_VELVET_ID:
eval = bsdf_ashikhmin_velvet_eval_transmit(sc, ccl_fetch(sd, I), omega_in, pdf);
break;
case CLOSURE_BSDF_DIFFUSE_TOON_ID:
eval = bsdf_diffuse_toon_eval_transmit(sc, ccl_fetch(sd, I), omega_in, pdf);
break;
case CLOSURE_BSDF_GLOSSY_TOON_ID:
eval = bsdf_glossy_toon_eval_transmit(sc, ccl_fetch(sd, I), omega_in, pdf);
break;
case CLOSURE_BSDF_HAIR_REFLECTION_ID:
eval = bsdf_hair_reflection_eval_transmit(sc, ccl_fetch(sd, I), omega_in, pdf);
break;
case CLOSURE_BSDF_HAIR_TRANSMISSION_ID:
eval = bsdf_hair_transmission_eval_transmit(sc, ccl_fetch(sd, I), omega_in, pdf);
break;
#endif
#ifdef __VOLUME__
case CLOSURE_VOLUME_HENYEY_GREENSTEIN_ID:
eval = volume_henyey_greenstein_eval_phase(sc, ccl_fetch(sd, I), omega_in, pdf);
break;
#endif
default:
eval = make_float3(0.0f, 0.0f, 0.0f);
break;
}
}
return eval;
}
ccl_device void bsdf_blur(KernelGlobals *kg, ShaderClosure *sc, float roughness)
{
/* ToDo: do we want to blur volume closures? */
#ifdef __OSL__
if(kg->osl && sc->prim) {
OSLShader::bsdf_blur(sc, roughness);
return;
}
#endif
#ifdef __SVM__
switch(sc->type) {
case CLOSURE_BSDF_MICROFACET_MULTI_GGX_ID:
case CLOSURE_BSDF_MICROFACET_MULTI_GGX_GLASS_ID:
bsdf_microfacet_multi_ggx_blur(sc, roughness);
break;
case CLOSURE_BSDF_MICROFACET_GGX_ID:
case CLOSURE_BSDF_MICROFACET_GGX_ANISO_ID:
case CLOSURE_BSDF_MICROFACET_GGX_REFRACTION_ID:
bsdf_microfacet_ggx_blur(sc, roughness);
break;
case CLOSURE_BSDF_MICROFACET_BECKMANN_ID:
case CLOSURE_BSDF_MICROFACET_BECKMANN_ANISO_ID:
case CLOSURE_BSDF_MICROFACET_BECKMANN_REFRACTION_ID:
bsdf_microfacet_beckmann_blur(sc, roughness);
break;
case CLOSURE_BSDF_ASHIKHMIN_SHIRLEY_ID:
case CLOSURE_BSDF_ASHIKHMIN_SHIRLEY_ANISO_ID:
bsdf_ashikhmin_shirley_blur(sc, roughness);
break;
default:
break;
}
#endif
}
CCL_NAMESPACE_END
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