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blender/intern/cycles/kernel/closure/bsdf_microfacet.h
Brecht Van Lommel d43682d51b Cycles: Subsurface Scattering 
New features:

* Bump mapping now works with SSS
* Texture Blur factor for SSS, see the documentation for details:
http://wiki.blender.org/index.php/Doc:2.6/Manual/Render/Cycles/Nodes/Shaders#Subsurface_Scattering

Work in progress for feedback:

Initial implementation of the "BSSRDF Importance Sampling" paper, which uses
a different importance sampling method. It gives better quality results in
many ways, with the availability of both Cubic and Gaussian falloff functions,
but also tends to be more noisy when using the progressive integrator and does
not give great results with some geometry. It works quite well for the
non-progressive integrator and is often less noisy there.

This code may still change a lot, so unless you're testing it may be best to
stick to the Compatible falloff function.

Skin test render and file that takes advantage of the gaussian falloff:
http://www.pasteall.org/pic/show.php?id=57661
http://www.pasteall.org/pic/show.php?id=57662
http://www.pasteall.org/blend/23501
2013-08-18 14:15:57 +00:00

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/*
* Adapted from Open Shading Language with this license:
*
* Copyright (c) 2009-2010 Sony Pictures Imageworks Inc., et al.
* All Rights Reserved.
*
* Modifications Copyright 2011, Blender Foundation.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of Sony Pictures Imageworks nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef __BSDF_MICROFACET_H__
#define __BSDF_MICROFACET_H__
CCL_NAMESPACE_BEGIN
/* GGX */
__device int bsdf_microfacet_ggx_setup(ShaderClosure *sc)
{
sc->data0 = clamp(sc->data0, 0.0f, 1.0f); /* m_ag */
sc->type = CLOSURE_BSDF_MICROFACET_GGX_ID;
return SD_BSDF|SD_BSDF_HAS_EVAL|SD_BSDF_GLOSSY;
}
__device int bsdf_microfacet_ggx_refraction_setup(ShaderClosure *sc)
{
sc->data0 = clamp(sc->data0, 0.0f, 1.0f); /* m_ag */
sc->type = CLOSURE_BSDF_MICROFACET_GGX_REFRACTION_ID;
return SD_BSDF|SD_BSDF_HAS_EVAL|SD_BSDF_GLOSSY;
}
__device void bsdf_microfacet_ggx_blur(ShaderClosure *sc, float roughness)
{
sc->data0 = fmaxf(roughness, sc->data0); /* m_ag */
}
__device float3 bsdf_microfacet_ggx_eval_reflect(const ShaderClosure *sc, const float3 I, const float3 omega_in, float *pdf)
{
float m_ag = max(sc->data0, 1e-4f);
int m_refractive = sc->type == CLOSURE_BSDF_MICROFACET_GGX_REFRACTION_ID;
float3 N = sc->N;
if(m_refractive || m_ag <= 1e-4f)
return make_float3 (0, 0, 0);
float cosNO = dot(N, I);
float cosNI = dot(N, omega_in);
if(cosNI > 0 && cosNO > 0) {
// get half vector
float3 Hr = normalize(omega_in + I);
// eq. 20: (F*G*D)/(4*in*on)
// eq. 33: first we calculate D(m) with m=Hr:
float alpha2 = m_ag * m_ag;
float cosThetaM = dot(N, Hr);
float cosThetaM2 = cosThetaM * cosThetaM;
float tanThetaM2 = (1 - cosThetaM2) / cosThetaM2;
float cosThetaM4 = cosThetaM2 * cosThetaM2;
float D = alpha2 / (M_PI_F * cosThetaM4 * (alpha2 + tanThetaM2) * (alpha2 + tanThetaM2));
// eq. 34: now calculate G1(i,m) and G1(o,m)
float G1o = 2 / (1 + safe_sqrtf(1 + alpha2 * (1 - cosNO * cosNO) / (cosNO * cosNO)));
float G1i = 2 / (1 + safe_sqrtf(1 + alpha2 * (1 - cosNI * cosNI) / (cosNI * cosNI)));
float G = G1o * G1i;
float out = (G * D) * 0.25f / cosNO;
// eq. 24
float pm = D * cosThetaM;
// convert into pdf of the sampled direction
// eq. 38 - but see also:
// eq. 17 in http://www.graphics.cornell.edu/~bjw/wardnotes.pdf
*pdf = pm * 0.25f / dot(Hr, I);
return make_float3 (out, out, out);
}
return make_float3 (0, 0, 0);
}
__device float3 bsdf_microfacet_ggx_eval_transmit(const ShaderClosure *sc, const float3 I, const float3 omega_in, float *pdf)
{
float m_ag = max(sc->data0, 1e-4f);
float m_eta = sc->data1;
int m_refractive = sc->type == CLOSURE_BSDF_MICROFACET_GGX_REFRACTION_ID;
float3 N = sc->N;
if(!m_refractive || m_ag <= 1e-4f)
return make_float3 (0, 0, 0);
float cosNO = dot(N, I);
float cosNI = dot(N, omega_in);
if(cosNO <= 0 || cosNI >= 0)
return make_float3 (0, 0, 0); // vectors on same side -- not possible
// compute half-vector of the refraction (eq. 16)
float3 ht = -(m_eta * omega_in + I);
float3 Ht = normalize(ht);
float cosHO = dot(Ht, I);
float cosHI = dot(Ht, omega_in);
// eq. 33: first we calculate D(m) with m=Ht:
float alpha2 = m_ag * m_ag;
float cosThetaM = dot(N, Ht);
float cosThetaM2 = cosThetaM * cosThetaM;
float tanThetaM2 = (1 - cosThetaM2) / cosThetaM2;
float cosThetaM4 = cosThetaM2 * cosThetaM2;
float D = alpha2 / (M_PI_F * cosThetaM4 * (alpha2 + tanThetaM2) * (alpha2 + tanThetaM2));
// eq. 34: now calculate G1(i,m) and G1(o,m)
float G1o = 2 / (1 + safe_sqrtf(1 + alpha2 * (1 - cosNO * cosNO) / (cosNO * cosNO)));
float G1i = 2 / (1 + safe_sqrtf(1 + alpha2 * (1 - cosNI * cosNI) / (cosNI * cosNI)));
float G = G1o * G1i;
// probability
float invHt2 = 1 / dot(ht, ht);
*pdf = D * fabsf(cosThetaM) * (fabsf(cosHI) * (m_eta * m_eta)) * invHt2;
float out = (fabsf(cosHI * cosHO) * (m_eta * m_eta) * (G * D) * invHt2) / cosNO;
return make_float3 (out, out, out);
}
__device int bsdf_microfacet_ggx_sample(const ShaderClosure *sc, float3 Ng, float3 I, float3 dIdx, float3 dIdy, float randu, float randv, float3 *eval, float3 *omega_in, float3 *domega_in_dx, float3 *domega_in_dy, float *pdf)
{
float m_ag = sc->data0;
int m_refractive = sc->type == CLOSURE_BSDF_MICROFACET_GGX_REFRACTION_ID;
float3 N = sc->N;
float cosNO = dot(N, I);
if(cosNO > 0) {
float3 X, Y, Z = N;
make_orthonormals(Z, &X, &Y);
// generate a random microfacet normal m
// eq. 35,36:
// we take advantage of cos(atan(x)) == 1/sqrt(1+x^2)
//tttt and sin(atan(x)) == x/sqrt(1+x^2)
float alpha2 = m_ag * m_ag;
float tanThetaM2 = alpha2 * randu / (1 - randu);
float cosThetaM = 1 / safe_sqrtf(1 + tanThetaM2);
float sinThetaM = cosThetaM * safe_sqrtf(tanThetaM2);
float phiM = M_2PI_F * randv;
float3 m = (cosf(phiM) * sinThetaM) * X +
(sinf(phiM) * sinThetaM) * Y +
cosThetaM * Z;
if(!m_refractive) {
float cosMO = dot(m, I);
if(cosMO > 0) {
// eq. 39 - compute actual reflected direction
*omega_in = 2 * cosMO * m - I;
if(dot(Ng, *omega_in) > 0) {
if (m_ag <= 1e-4f) {
// some high number for MIS
*pdf = 1e6f;
*eval = make_float3(1e6f, 1e6f, 1e6f);
}
else {
// microfacet normal is visible to this ray
// eq. 33
float cosThetaM2 = cosThetaM * cosThetaM;
float cosThetaM4 = cosThetaM2 * cosThetaM2;
float D = alpha2 / (M_PI_F * cosThetaM4 * (alpha2 + tanThetaM2) * (alpha2 + tanThetaM2));
// eq. 24
float pm = D * cosThetaM;
// convert into pdf of the sampled direction
// eq. 38 - but see also:
// eq. 17 in http://www.graphics.cornell.edu/~bjw/wardnotes.pdf
*pdf = pm * 0.25f / cosMO;
// eval BRDF*cosNI
float cosNI = dot(N, *omega_in);
// eq. 34: now calculate G1(i,m) and G1(o,m)
float G1o = 2 / (1 + safe_sqrtf(1 + alpha2 * (1 - cosNO * cosNO) / (cosNO * cosNO)));
float G1i = 2 / (1 + safe_sqrtf(1 + alpha2 * (1 - cosNI * cosNI) / (cosNI * cosNI)));
float G = G1o * G1i;
// eq. 20: (F*G*D)/(4*in*on)
float out = (G * D) * 0.25f / cosNO;
*eval = make_float3(out, out, out);
}
#ifdef __RAY_DIFFERENTIALS__
*domega_in_dx = (2 * dot(m, dIdx)) * m - dIdx;
*domega_in_dy = (2 * dot(m, dIdy)) * m - dIdy;
#endif
}
}
}
else {
// CAUTION: the i and o variables are inverted relative to the paper
// eq. 39 - compute actual refractive direction
float3 R, T;
#ifdef __RAY_DIFFERENTIALS__
float3 dRdx, dRdy, dTdx, dTdy;
#endif
float m_eta = sc->data1;
bool inside;
fresnel_dielectric(m_eta, m, I, &R, &T,
#ifdef __RAY_DIFFERENTIALS__
dIdx, dIdy, &dRdx, &dRdy, &dTdx, &dTdy,
#endif
&inside);
if(!inside) {
*omega_in = T;
#ifdef __RAY_DIFFERENTIALS__
*domega_in_dx = dTdx;
*domega_in_dy = dTdy;
#endif
if (m_ag <= 1e-4f) {
// some high number for MIS
*pdf = 1e6f;
*eval = make_float3(1e6f, 1e6f, 1e6f);
}
else {
// eq. 33
float cosThetaM2 = cosThetaM * cosThetaM;
float cosThetaM4 = cosThetaM2 * cosThetaM2;
float D = alpha2 / (M_PI_F * cosThetaM4 * (alpha2 + tanThetaM2) * (alpha2 + tanThetaM2));
// eq. 24
float pm = D * cosThetaM;
// eval BRDF*cosNI
float cosNI = dot(N, *omega_in);
// eq. 34: now calculate G1(i,m) and G1(o,m)
float G1o = 2 / (1 + safe_sqrtf(1 + alpha2 * (1 - cosNO * cosNO) / (cosNO * cosNO)));
float G1i = 2 / (1 + safe_sqrtf(1 + alpha2 * (1 - cosNI * cosNI) / (cosNI * cosNI)));
float G = G1o * G1i;
// eq. 21
float cosHI = dot(m, *omega_in);
float cosHO = dot(m, I);
float Ht2 = m_eta * cosHI + cosHO;
Ht2 *= Ht2;
float out = (fabsf(cosHI * cosHO) * (m_eta * m_eta) * (G * D)) / (cosNO * Ht2);
// eq. 38 and eq. 17
*pdf = pm * (m_eta * m_eta) * fabsf(cosHI) / Ht2;
*eval = make_float3(out, out, out);
}
}
}
}
return (m_refractive) ? LABEL_TRANSMIT|LABEL_GLOSSY : LABEL_REFLECT|LABEL_GLOSSY;
}
/* BECKMANN */
__device int bsdf_microfacet_beckmann_setup(ShaderClosure *sc)
{
sc->data0 = clamp(sc->data0, 0.0f, 1.0f); /* m_ab */
sc->type = CLOSURE_BSDF_MICROFACET_BECKMANN_ID;
return SD_BSDF|SD_BSDF_HAS_EVAL|SD_BSDF_GLOSSY;
}
__device int bsdf_microfacet_beckmann_refraction_setup(ShaderClosure *sc)
{
sc->data0 = clamp(sc->data0, 0.0f, 1.0f); /* m_ab */
sc->type = CLOSURE_BSDF_MICROFACET_BECKMANN_REFRACTION_ID;
return SD_BSDF|SD_BSDF_HAS_EVAL|SD_BSDF_GLOSSY;
}
__device void bsdf_microfacet_beckmann_blur(ShaderClosure *sc, float roughness)
{
sc->data0 = fmaxf(roughness, sc->data0); /* m_ab */
}
__device float3 bsdf_microfacet_beckmann_eval_reflect(const ShaderClosure *sc, const float3 I, const float3 omega_in, float *pdf)
{
float m_ab = max(sc->data0, 1e-4f);
int m_refractive = sc->type == CLOSURE_BSDF_MICROFACET_BECKMANN_REFRACTION_ID;
float3 N = sc->N;
if(m_refractive || m_ab <= 1e-4f)
return make_float3 (0, 0, 0);
float cosNO = dot(N, I);
float cosNI = dot(N, omega_in);
if(cosNO > 0 && cosNI > 0) {
// get half vector
float3 Hr = normalize(omega_in + I);
// eq. 20: (F*G*D)/(4*in*on)
// eq. 25: first we calculate D(m) with m=Hr:
float alpha2 = m_ab * m_ab;
float cosThetaM = dot(N, Hr);
float cosThetaM2 = cosThetaM * cosThetaM;
float tanThetaM2 = (1 - cosThetaM2) / cosThetaM2;
float cosThetaM4 = cosThetaM2 * cosThetaM2;
float D = expf(-tanThetaM2 / alpha2) / (M_PI_F * alpha2 * cosThetaM4);
// eq. 26, 27: now calculate G1(i,m) and G1(o,m)
float ao = 1 / (m_ab * safe_sqrtf((1 - cosNO * cosNO) / (cosNO * cosNO)));
float ai = 1 / (m_ab * safe_sqrtf((1 - cosNI * cosNI) / (cosNI * cosNI)));
float G1o = ao < 1.6f ? (3.535f * ao + 2.181f * ao * ao) / (1 + 2.276f * ao + 2.577f * ao * ao) : 1.0f;
float G1i = ai < 1.6f ? (3.535f * ai + 2.181f * ai * ai) / (1 + 2.276f * ai + 2.577f * ai * ai) : 1.0f;
float G = G1o * G1i;
float out = (G * D) * 0.25f / cosNO;
// eq. 24
float pm = D * cosThetaM;
// convert into pdf of the sampled direction
// eq. 38 - but see also:
// eq. 17 in http://www.graphics.cornell.edu/~bjw/wardnotes.pdf
*pdf = pm * 0.25f / dot(Hr, I);
return make_float3 (out, out, out);
}
return make_float3 (0, 0, 0);
}
__device float3 bsdf_microfacet_beckmann_eval_transmit(const ShaderClosure *sc, const float3 I, const float3 omega_in, float *pdf)
{
float m_ab = max(sc->data0, 1e-4f);
float m_eta = sc->data1;
int m_refractive = sc->type == CLOSURE_BSDF_MICROFACET_BECKMANN_REFRACTION_ID;
float3 N = sc->N;
if(!m_refractive || m_ab <= 1e-4f)
return make_float3 (0, 0, 0);
float cosNO = dot(N, I);
float cosNI = dot(N, omega_in);
if(cosNO <= 0 || cosNI >= 0)
return make_float3 (0, 0, 0);
// compute half-vector of the refraction (eq. 16)
float3 ht = -(m_eta * omega_in + I);
float3 Ht = normalize(ht);
float cosHO = dot(Ht, I);
float cosHI = dot(Ht, omega_in);
// eq. 33: first we calculate D(m) with m=Ht:
float alpha2 = m_ab * m_ab;
float cosThetaM = min(dot(N, Ht), 1.0f);
float cosThetaM2 = cosThetaM * cosThetaM;
float tanThetaM2 = (1 - cosThetaM2) / cosThetaM2;
float cosThetaM4 = cosThetaM2 * cosThetaM2;
float D = expf(-tanThetaM2 / alpha2) / (M_PI_F * alpha2 * cosThetaM4);
// eq. 26, 27: now calculate G1(i,m) and G1(o,m)
float ao = 1 / (m_ab * safe_sqrtf((1 - cosNO * cosNO) / (cosNO * cosNO)));
float ai = 1 / (m_ab * safe_sqrtf((1 - cosNI * cosNI) / (cosNI * cosNI)));
float G1o = ao < 1.6f ? (3.535f * ao + 2.181f * ao * ao) / (1 + 2.276f * ao + 2.577f * ao * ao) : 1.0f;
float G1i = ai < 1.6f ? (3.535f * ai + 2.181f * ai * ai) / (1 + 2.276f * ai + 2.577f * ai * ai) : 1.0f;
float G = G1o * G1i;
// probability
float invHt2 = 1 / dot(ht, ht);
*pdf = D * fabsf(cosThetaM) * (fabsf(cosHI) * (m_eta * m_eta)) * invHt2;
float out = (fabsf(cosHI * cosHO) * (m_eta * m_eta) * (G * D) * invHt2) / cosNO;
return make_float3 (out, out, out);
}
__device int bsdf_microfacet_beckmann_sample(const ShaderClosure *sc, float3 Ng, float3 I, float3 dIdx, float3 dIdy, float randu, float randv, float3 *eval, float3 *omega_in, float3 *domega_in_dx, float3 *domega_in_dy, float *pdf)
{
float m_ab = sc->data0;
int m_refractive = sc->type == CLOSURE_BSDF_MICROFACET_BECKMANN_REFRACTION_ID;
float3 N = sc->N;
float cosNO = dot(N, I);
if(cosNO > 0) {
float3 X, Y, Z = N;
make_orthonormals(Z, &X, &Y);
// generate a random microfacet normal m
// eq. 35,36:
// we take advantage of cos(atan(x)) == 1/sqrt(1+x^2)
//tttt and sin(atan(x)) == x/sqrt(1+x^2)
float alpha2 = m_ab * m_ab;
float tanThetaM, cosThetaM;
if(alpha2 == 0.0f) {
tanThetaM = 0.0f;
cosThetaM = 1.0f;
}
else {
tanThetaM = safe_sqrtf(-alpha2 * logf(1 - randu));
cosThetaM = 1 / safe_sqrtf(1 + tanThetaM * tanThetaM);
}
float sinThetaM = cosThetaM * tanThetaM;
float phiM = M_2PI_F * randv;
float3 m = (cosf(phiM) * sinThetaM) * X +
(sinf(phiM) * sinThetaM) * Y +
cosThetaM * Z;
if(!m_refractive) {
float cosMO = dot(m, I);
if(cosMO > 0) {
// eq. 39 - compute actual reflected direction
*omega_in = 2 * cosMO * m - I;
if(dot(Ng, *omega_in) > 0) {
if (m_ab <= 1e-4f) {
// some high number for MIS
*pdf = 1e6f;
*eval = make_float3(1e6f, 1e6f, 1e6f);
}
else {
// microfacet normal is visible to this ray
// eq. 25
float cosThetaM2 = cosThetaM * cosThetaM;
float tanThetaM2 = tanThetaM * tanThetaM;
float cosThetaM4 = cosThetaM2 * cosThetaM2;
float D = expf(-tanThetaM2 / alpha2) / (M_PI_F * alpha2 * cosThetaM4);
// eq. 24
float pm = D * cosThetaM;
// convert into pdf of the sampled direction
// eq. 38 - but see also:
// eq. 17 in http://www.graphics.cornell.edu/~bjw/wardnotes.pdf
*pdf = pm * 0.25f / cosMO;
// Eval BRDF*cosNI
float cosNI = dot(N, *omega_in);
// eq. 26, 27: now calculate G1(i,m) and G1(o,m)
float ao = 1 / (m_ab * safe_sqrtf((1 - cosNO * cosNO) / (cosNO * cosNO)));
float ai = 1 / (m_ab * safe_sqrtf((1 - cosNI * cosNI) / (cosNI * cosNI)));
float G1o = ao < 1.6f ? (3.535f * ao + 2.181f * ao * ao) / (1 + 2.276f * ao + 2.577f * ao * ao) : 1.0f;
float G1i = ai < 1.6f ? (3.535f * ai + 2.181f * ai * ai) / (1 + 2.276f * ai + 2.577f * ai * ai) : 1.0f;
float G = G1o * G1i;
// eq. 20: (F*G*D)/(4*in*on)
float out = (G * D) * 0.25f / cosNO;
*eval = make_float3(out, out, out);
}
#ifdef __RAY_DIFFERENTIALS__
*domega_in_dx = (2 * dot(m, dIdx)) * m - dIdx;
*domega_in_dy = (2 * dot(m, dIdy)) * m - dIdy;
#endif
}
}
}
else {
// CAUTION: the i and o variables are inverted relative to the paper
// eq. 39 - compute actual refractive direction
float3 R, T;
#ifdef __RAY_DIFFERENTIALS__
float3 dRdx, dRdy, dTdx, dTdy;
#endif
float m_eta = sc->data1;
bool inside;
fresnel_dielectric(m_eta, m, I, &R, &T,
#ifdef __RAY_DIFFERENTIALS__
dIdx, dIdy, &dRdx, &dRdy, &dTdx, &dTdy,
#endif
&inside);
if(!inside) {
*omega_in = T;
#ifdef __RAY_DIFFERENTIALS__
*domega_in_dx = dTdx;
*domega_in_dy = dTdy;
#endif
if (m_ab <= 1e-4f) {
// some high number for MIS
*pdf = 1e6f;
*eval = make_float3(1e6f, 1e6f, 1e6f);
}
else {
// eq. 33
float cosThetaM2 = cosThetaM * cosThetaM;
float tanThetaM2 = tanThetaM * tanThetaM;
float cosThetaM4 = cosThetaM2 * cosThetaM2;
float D = expf(-tanThetaM2 / alpha2) / (M_PI_F * alpha2 * cosThetaM4);
// eq. 24
float pm = D * cosThetaM;
// eval BRDF*cosNI
float cosNI = dot(N, *omega_in);
// eq. 26, 27: now calculate G1(i,m) and G1(o,m)
float ao = 1 / (m_ab * safe_sqrtf((1 - cosNO * cosNO) / (cosNO * cosNO)));
float ai = 1 / (m_ab * safe_sqrtf((1 - cosNI * cosNI) / (cosNI * cosNI)));
float G1o = ao < 1.6f ? (3.535f * ao + 2.181f * ao * ao) / (1 + 2.276f * ao + 2.577f * ao * ao) : 1.0f;
float G1i = ai < 1.6f ? (3.535f * ai + 2.181f * ai * ai) / (1 + 2.276f * ai + 2.577f * ai * ai) : 1.0f;
float G = G1o * G1i;
// eq. 21
float cosHI = dot(m, *omega_in);
float cosHO = dot(m, I);
float Ht2 = m_eta * cosHI + cosHO;
Ht2 *= Ht2;
float out = (fabsf(cosHI * cosHO) * (m_eta * m_eta) * (G * D)) / (cosNO * Ht2);
// eq. 38 and eq. 17
*pdf = pm * (m_eta * m_eta) * fabsf(cosHI) / Ht2;
*eval = make_float3(out, out, out);
}
}
}
}
return (m_refractive) ? LABEL_TRANSMIT|LABEL_GLOSSY : LABEL_REFLECT|LABEL_GLOSSY;
}
CCL_NAMESPACE_END
#endif /* __BSDF_MICROFACET_H__ */
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