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significant improvements to the rough glass sampling code

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Wenzel Jakob 2010-12-02 01:10:43 +01:00
parent 683c5e463d
commit 67ab96cba8
2 changed files with 47 additions and 37 deletions
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2
data/blender/mitsuba/matpreview/matpreview.xml
View File

@ -41,7 +41,7 @@
</luminaire>
<bsdf id="__diffmat" type="lambertian">
<rgb name="reflectance" value="0.5 0.5 0.5"/>
<rgb name="reflectance" value="0.18 0.18 0.18"/>
</bsdf>
<texture id="__planetex" type="checkerboard">

82
src/bsdfs/roughglass.cpp
View File

@ -43,8 +43,6 @@ public:
m_type[0] = EGlossyReflection;
m_type[1] = EGlossyTransmission;
m_combinedType = m_type[0] | m_type[1];
m_transmissionSamplingWeight = .5f;
m_reflectionSamplingWeight = 1 - m_transmissionSamplingWeight;
m_usesRayDifferentials = false;
}
@ -55,8 +53,6 @@ public:
m_alphaB = stream->readFloat();
m_intIOR = stream->readFloat();
m_extIOR = stream->readFloat();
m_reflectionSamplingWeight = stream->readFloat();
m_transmissionSamplingWeight = stream->readFloat();
m_componentCount = 2;
m_type = new unsigned int[m_componentCount];
@ -78,9 +74,9 @@ public:
* Beckmann distribution function for gaussian random surfaces
* @param thetaM Tangent of the angle between M and N.
*/
Float beckmannD(const Vector &m) const {
Float ex = Frame::tanTheta(m) / m_alphaB;
Float value = std::exp(-(ex*ex)) / (M_PI * m_alphaB*m_alphaB *
inline Float beckmannD(const Vector &m, Float alphaB) const {
Float ex = Frame::tanTheta(m) / alphaB;
Float value = std::exp(-(ex*ex)) / (M_PI * alphaB*alphaB *
std::pow(Frame::cosTheta(m), (Float) 4.0f));
if (value < Epsilon)
return 0;
@ -91,8 +87,8 @@ public:
* Sample microsurface normals according to
* the Beckmann distribution
*/
Normal sampleBeckmannD(Point2 sample) const {
Float thetaM = std::atan(std::sqrt(-m_alphaB*m_alphaB
Normal sampleBeckmannD(Point2 sample, Float alphaB) const {
Float thetaM = std::atan(std::sqrt(-alphaB*alphaB
* std::log(1.0f - sample.x)));
Float phiM = (2.0f * M_PI) * sample.y;
return Normal(sphericalDirection(thetaM, phiM));
@ -187,7 +183,7 @@ public:
Float F = fresnel(dot(bRec.wi, Hr), m_extIOR, m_intIOR);
/* Microsurface normal distribution */
Float D = beckmannD(Hr);
Float D = beckmannD(Hr, m_alphaB);
/* Smith's shadow-masking function for the Beckmann distribution */
Float G = smithBeckmannG1(bRec.wi, Hr) * smithBeckmannG1(bRec.wo, Hr);
@ -214,7 +210,7 @@ public:
Float F = 1.0f - fresnel(dot(bRec.wi, Ht), m_extIOR, m_intIOR);
/* Microsurface normal distribution */
Float D = beckmannD(Ht);
Float D = beckmannD(Ht, m_alphaB);
/* Smith's shadow-masking function for the Beckmann distribution */
Float G;
@ -257,7 +253,7 @@ public:
return result;
}
inline Float pdfReflection(const BSDFQueryRecord &bRec) const {
inline Float pdfReflection(const BSDFQueryRecord &bRec, Float alphaB) const {
if (Frame::cosTheta(bRec.wi) * Frame::cosTheta(bRec.wo) < 0)
return 0.0f;
@ -267,10 +263,10 @@ public:
/* Jacobian of the half-direction transform */
Float dwhr_dwo = 1.0f / (4.0f * absDot(bRec.wo, Hr));
return beckmannD(Hr) * std::abs(Frame::cosTheta(Hr)) * dwhr_dwo;
return beckmannD(Hr, alphaB) * std::abs(Frame::cosTheta(Hr)) * dwhr_dwo;
}
inline Float pdfTransmission(const BSDFQueryRecord &bRec) const {
inline Float pdfTransmission(const BSDFQueryRecord &bRec, Float alphaB) const {
Float etaI = m_extIOR, etaO = m_intIOR;
if (Frame::cosTheta(bRec.wi) * Frame::cosTheta(bRec.wo) >= 0)
@ -285,7 +281,7 @@ public:
Float sqrtDenom = etaI * dot(bRec.wi, Ht) + etaO * dot(bRec.wo, Ht);
Float dwht_dwo = (etaO*etaO * absDot(bRec.wo, Ht)) / (sqrtDenom*sqrtDenom);
return beckmannD(Ht) * std::abs(Frame::cosTheta(Ht)) * dwht_dwo;
return beckmannD(Ht, alphaB) * std::abs(Frame::cosTheta(Ht)) * dwht_dwo;
}
Float pdf(const BSDFQueryRecord &bRec) const {
@ -294,21 +290,30 @@ public:
bool hasTransmission = (bRec.typeMask & EGlossyTransmission)
&& (bRec.component == -1 || bRec.component == 1);
/* Suggestion by Bruce walter: sample using a slightly different
value of alphaB. This in practice limits the weights to
values <= 4. See also \ref sample() */
Float alphaB = m_alphaB * (1.2f - 0.2f * std::sqrt(
std::abs(Frame::cosTheta(bRec.wi))));
if (hasReflection && hasTransmission) {
return m_reflectionSamplingWeight * pdfReflection(bRec) +
m_transmissionSamplingWeight * pdfTransmission(bRec);
Float fr = fresnel(Frame::cosTheta(bRec.wi), m_extIOR, m_intIOR);
fr = std::min(std::max(fr, (Float) 0.05f), (Float) 0.95f);
return fr * pdfReflection(bRec, alphaB) +
(1-fr) * pdfTransmission(bRec, alphaB);
} else if (hasReflection) {
return pdfReflection(bRec);
return pdfReflection(bRec, alphaB);
} else if (hasTransmission) {
return pdfTransmission(bRec);
return pdfTransmission(bRec, alphaB);
}
return 0.0f;
}
inline Spectrum sampleReflection(BSDFQueryRecord &bRec) const {
inline Spectrum sampleReflection(BSDFQueryRecord &bRec, Float alphaB) const {
/* Sample M, the microsurface normal */
Normal m = sampleBeckmannD(bRec.sample);
Normal m = sampleBeckmannD(bRec.sample, alphaB);
/* Perfect specular reflection along the microsurface normal */
bRec.wo = reflect(bRec.wi, m);
@ -322,13 +327,14 @@ public:
return f(bRec) / pdf(bRec);
}
inline Spectrum sampleTransmission(BSDFQueryRecord &bRec) const {
inline Spectrum sampleTransmission(BSDFQueryRecord &bRec, Float alphaB) const {
/* Sample M, the microsurface normal */
Frame mFrame(sampleBeckmannD(bRec.sample));
Frame mFrame(sampleBeckmannD(bRec.sample, alphaB));
/* Perfect specular reflection along the microsurface normal */
if (refract(mFrame.toLocal(bRec.wi), bRec.wo, bRec.quantity) == 0)
return Spectrum(0.0f);
bRec.wo = mFrame.toWorld(bRec.wo);
bRec.sampledComponent = 1;
@ -346,19 +352,27 @@ public:
bool hasTransmission = (bRec.typeMask & EGlossyTransmission)
&& (bRec.component == -1 || bRec.component == 1);
/* Suggestion by Bruce walter: sample using a slightly different
value of alphaB. This in practice limits the weights to
values <= 4. The change is of course also accounted for
in \ref pdf(), hence no error is introduced. */
Float alphaB = m_alphaB * (1.2f - 0.2f * std::sqrt(
std::abs(Frame::cosTheta(bRec.wi))));
if (hasReflection && hasTransmission) {
if (bRec.sample.x < m_reflectionSamplingWeight) {
bRec.sample.x = bRec.sample.x / m_reflectionSamplingWeight;
return sampleReflection(bRec);
Float fr = fresnel(Frame::cosTheta(bRec.wi), m_extIOR, m_intIOR);
fr = std::min(std::max(fr, (Float) 0.05f), (Float) 0.95f);
if (bRec.sample.x < fr) {
bRec.sample.x /= fr;
return sampleReflection(bRec, alphaB);
} else {
bRec.sample.x = (bRec.sample.x - m_reflectionSamplingWeight)
/ m_transmissionSamplingWeight;
return sampleTransmission(bRec);
bRec.sample.x = (bRec.sample.x - fr) / (1-fr);
return sampleTransmission(bRec, alphaB);
}
} else if (hasReflection) {
return sampleReflection(bRec);
return sampleReflection(bRec, alphaB);
} else if (hasTransmission) {
return sampleTransmission(bRec);
return sampleTransmission(bRec, alphaB);
}
return Spectrum(0.0f);
@ -372,8 +386,6 @@ public:
stream->writeFloat(m_alphaB);
stream->writeFloat(m_intIOR);
stream->writeFloat(m_extIOR);
stream->writeFloat(m_reflectionSamplingWeight);
stream->writeFloat(m_transmissionSamplingWeight);
}
std::string toString() const {
@ -393,8 +405,6 @@ private:
Spectrum m_specularReflectance;
Spectrum m_specularTransmittance;
Float m_alphaB, m_intIOR, m_extIOR;
Float m_reflectionSamplingWeight;
Float m_transmissionSamplingWeight;
};
MTS_IMPLEMENT_CLASS_S(RoughGlass, false, BSDF)