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texturable specular reflectance for coating + roughcoating

metadata
Wenzel Jakob 2011-09-19 19:19:00 -04:00
parent 2b9057cf64
commit 30a93f4bbc
2 changed files with 53 additions and 18 deletions
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42
src/bsdfs/coating.cpp
View File

@ -35,6 +35,9 @@ MTS_NAMESPACE_BEGIN
* model absorption --- should be specified in inverse units of \code{sigmaA})\default{1}} * model absorption --- should be specified in inverse units of \code{sigmaA})\default{1}}
* \parameter{sigmaA}{\Spectrum\Or\Texture}{The absorption coefficient of the * \parameter{sigmaA}{\Spectrum\Or\Texture}{The absorption coefficient of the
* coating layer. \default{0, i.e. there is no absorption}} * coating layer. \default{0, i.e. there is no absorption}}
* \parameter{specular\showbreak Transmittance}{\Spectrum\Or\Texture}{Optional
* factor that can be used to modulate the specular transmission component. Note
* that for physical realism, this parameter should never be touched. \default{1.0}}
* \parameter{\Unnamed}{\BSDF}{A nested BSDF model that should be coated.} * \parameter{\Unnamed}{\BSDF}{A nested BSDF model that should be coated.}
* } * }
* *
@ -62,13 +65,7 @@ MTS_NAMESPACE_BEGIN
* Therefore, users are discouraged to use this plugin to coat smooth * Therefore, users are discouraged to use this plugin to coat smooth
* diffuse materials, since there is a separately available plugin * diffuse materials, since there is a separately available plugin
* named \pluginref{plastic}, which covers the same case and does not * named \pluginref{plastic}, which covers the same case and does not
* suffer from energy loss. * suffer from energy loss.\newpage
*
* Evaluating the internal component of this model entails refracting the
* incident and exitant rays through the dielectric interface, followed by
* querying the nested material with this modified direction pair. The result
* is attenuated by the two Fresnel transmittances and the absorption, if
* any.\newpage
* *
* \renderings{ * \renderings{
* \smallrendering{$\code{thickness}=0$}{bsdf_coating_0} * \smallrendering{$\code{thickness}=0$}{bsdf_coating_0}
@ -99,6 +96,13 @@ MTS_NAMESPACE_BEGIN
* \caption{Some interesting materials can be created simply by applying * \caption{Some interesting materials can be created simply by applying
* Mitsuba's material modifiers in different orders.} * Mitsuba's material modifiers in different orders.}
* } * }
*
* \subsubsection*{Technical details}
* Evaluating the internal component of this model entails refracting the
* incident and exitant rays through the dielectric interface, followed by
* querying the nested material with this modified direction pair. The result
* is attenuated by the two Fresnel transmittances and the absorption, if
* any.
*/ */
class SmoothCoating : public BSDF { class SmoothCoating : public BSDF {
public: public:
@ -123,6 +127,10 @@ public:
m_sigmaA = new ConstantSpectrumTexture( m_sigmaA = new ConstantSpectrumTexture(
props.getSpectrum("sigmaA", Spectrum(0.0f))); props.getSpectrum("sigmaA", Spectrum(0.0f)));
/* Specifies a multiplier for the specular reflectance component */
m_specularReflectance = new ConstantSpectrumTexture(
props.getSpectrum("specularReflectance", Spectrum(1.0f)));
if (m_intIOR < 0 || m_extIOR < 0 || m_intIOR == m_extIOR) if (m_intIOR < 0 || m_extIOR < 0 || m_intIOR == m_extIOR)
Log(EError, "The interior and exterior indices of " Log(EError, "The interior and exterior indices of "
"refraction must be positive and differ!"); "refraction must be positive and differ!");
@ -135,6 +143,7 @@ public:
m_thickness = stream->readFloat(); m_thickness = stream->readFloat();
m_nested = static_cast<BSDF *>(manager->getInstance(stream)); m_nested = static_cast<BSDF *>(manager->getInstance(stream));
m_sigmaA = static_cast<Texture *>(manager->getInstance(stream)); m_sigmaA = static_cast<Texture *>(manager->getInstance(stream));
m_specularReflectance = static_cast<Texture *>(manager->getInstance(stream));
configure(); configure();
} }
@ -150,10 +159,12 @@ public:
for (int i=0; i<m_nested->getComponentCount(); ++i) for (int i=0; i<m_nested->getComponentCount(); ++i)
m_components.push_back(m_nested->getType(i) | extraFlags); m_components.push_back(m_nested->getType(i) | extraFlags);
m_components.push_back(EDeltaReflection | EFrontSide | EBackSide); m_components.push_back(EDeltaReflection | EFrontSide | EBackSide
| (m_specularReflectance->isConstant() ? 0 : ESpatiallyVarying));
m_usesRayDifferentials = m_nested->usesRayDifferentials() m_usesRayDifferentials = m_nested->usesRayDifferentials()
|| m_sigmaA->usesRayDifferentials(); || m_sigmaA->usesRayDifferentials()
|| m_specularReflectance->usesRayDifferentials();
/* Compute weights that further steer samples towards /* Compute weights that further steer samples towards
the specular or nested components */ the specular or nested components */
@ -162,6 +173,10 @@ public:
m_specularSamplingWeight = 1.0f / (avgAbsorption + 1.0f); m_specularSamplingWeight = 1.0f / (avgAbsorption + 1.0f);
/* Verify the input parameters and fix them if necessary */
m_specularReflectance = ensureEnergyConservation(
m_specularReflectance, "specularReflectance", 1.0f);
BSDF::configure(); BSDF::configure();
} }
@ -173,6 +188,7 @@ public:
stream->writeFloat(m_thickness); stream->writeFloat(m_thickness);
manager->serialize(stream, m_nested.get()); manager->serialize(stream, m_nested.get());
manager->serialize(stream, m_sigmaA.get()); manager->serialize(stream, m_sigmaA.get());
manager->serialize(stream, m_specularReflectance.get());
} }
void addChild(const std::string &name, ConfigurableObject *child) { void addChild(const std::string &name, ConfigurableObject *child) {
@ -238,8 +254,8 @@ public:
if (measure == EDiscrete && sampleSpecular && if (measure == EDiscrete && sampleSpecular &&
std::abs(1-dot(reflect(bRec.wi), bRec.wo)) < Epsilon) { std::abs(1-dot(reflect(bRec.wi), bRec.wo)) < Epsilon) {
return Spectrum(fresnel( return m_specularReflectance->getValue(bRec.its) *
std::abs(Frame::cosTheta(bRec.wi)), m_extIOR, m_intIOR)); fresnel(std::abs(Frame::cosTheta(bRec.wi)), m_extIOR, m_intIOR);
} else if (sampleNested) { } else if (sampleNested) {
Float R12, R21; Float R12, R21;
BSDFQueryRecord bRecInt(bRec); BSDFQueryRecord bRecInt(bRec);
@ -346,7 +362,7 @@ public:
bRec.sampledType = EDeltaReflection; bRec.sampledType = EDeltaReflection;
bRec.wo = reflect(bRec.wi); bRec.wo = reflect(bRec.wi);
pdf = sampleNested ? probSpecular : 1.0f; pdf = sampleNested ? probSpecular : 1.0f;
return Spectrum(R12) / pdf; return m_specularReflectance->getValue(bRec.its) * (R12/pdf);
} else { } else {
if (R12 == 1.0f) /* Total internal reflection */ if (R12 == 1.0f) /* Total internal reflection */
return Spectrum(0.0f); return Spectrum(0.0f);
@ -405,6 +421,7 @@ public:
<< " extIOR = " << m_extIOR << "," << endl << " extIOR = " << m_extIOR << "," << endl
<< " specularSamplingWeight = " << m_specularSamplingWeight << "," << endl << " specularSamplingWeight = " << m_specularSamplingWeight << "," << endl
<< " sigmaA = " << indent(m_sigmaA->toString()) << "," << endl << " sigmaA = " << indent(m_sigmaA->toString()) << "," << endl
<< " specularReflectance = " << indent(m_specularReflectance->toString()) << "," << endl
<< " thickness = " << m_thickness << "," << endl << " thickness = " << m_thickness << "," << endl
<< " nested = " << indent(m_nested.toString()) << endl << " nested = " << indent(m_nested.toString()) << endl
<< "]"; << "]";
@ -416,6 +433,7 @@ protected:
Float m_specularSamplingWeight; Float m_specularSamplingWeight;
Float m_intIOR, m_extIOR; Float m_intIOR, m_extIOR;
ref<Texture> m_sigmaA; ref<Texture> m_sigmaA;
ref<Texture> m_specularReflectance;
ref<BSDF> m_nested; ref<BSDF> m_nested;
Float m_thickness; Float m_thickness;
}; };

27
src/bsdfs/roughcoating.cpp
View File

@ -57,6 +57,9 @@ MTS_NAMESPACE_BEGIN
* numerically or using a known material name. \default{\texttt{air} / 1.000277}} * numerically or using a known material name. \default{\texttt{air} / 1.000277}}
* \parameter{sigmaA}{\Spectrum\Or\Texture}{The absorption coefficient of the * \parameter{sigmaA}{\Spectrum\Or\Texture}{The absorption coefficient of the
* coating layer. \default{0, i.e. there is no absorption}} * coating layer. \default{0, i.e. there is no absorption}}
* \parameter{specular\showbreak Transmittance}{\Spectrum\Or\Texture}{Optional
* factor that can be used to modulate the specular transmission component. Note
* that for physical realism, this parameter should never be touched. \default{1.0}}
* \parameter{\Unnamed}{\BSDF}{A nested BSDF model that should be coated.} * \parameter{\Unnamed}{\BSDF}{A nested BSDF model that should be coated.}
* }\vspace{-4mm} * }\vspace{-4mm}
* \renderings{ * \renderings{
@ -75,8 +78,8 @@ MTS_NAMESPACE_BEGIN
* \pluginref{coating} plugin produces specular highlights that are too sharp.} * \pluginref{coating} plugin produces specular highlights that are too sharp.}
* model that simulates a rough dielectric coating. It is essentially the * model that simulates a rough dielectric coating. It is essentially the
* roughened version of \pluginref{coating}. * roughened version of \pluginref{coating}.
* Any BSDF in Mitsuba can be coated using this plugin, and multiple coating * Any BSDF in Mitsuba can be coated using this plugin and multiple coating
* layers can even be applied in sequence. This allows designing interesting * layers can even be applied in sequence, which allows designing interesting
* custom materials. The coating layer can optionally be tinted (i.e. filled * custom materials. The coating layer can optionally be tinted (i.e. filled
* with an absorbing medium), in which case this model also accounts for the * with an absorbing medium), in which case this model also accounts for the
* directionally dependent absorption within the layer. * directionally dependent absorption within the layer.
@ -109,6 +112,10 @@ public:
m_sigmaA = new ConstantSpectrumTexture( m_sigmaA = new ConstantSpectrumTexture(
props.getSpectrum("sigmaA", Spectrum(0.0f))); props.getSpectrum("sigmaA", Spectrum(0.0f)));
/* Specifies a multiplier for the specular reflectance component */
m_specularReflectance = new ConstantSpectrumTexture(
props.getSpectrum("specularReflectance", Spectrum(1.0f)));
if (m_intIOR < 0 || m_extIOR < 0 || m_intIOR == m_extIOR) if (m_intIOR < 0 || m_extIOR < 0 || m_intIOR == m_extIOR)
Log(EError, "The interior and exterior indices of " Log(EError, "The interior and exterior indices of "
"refraction must be positive and differ!"); "refraction must be positive and differ!");
@ -134,6 +141,7 @@ public:
); );
m_nested = static_cast<BSDF *>(manager->getInstance(stream)); m_nested = static_cast<BSDF *>(manager->getInstance(stream));
m_sigmaA = static_cast<Texture *>(manager->getInstance(stream)); m_sigmaA = static_cast<Texture *>(manager->getInstance(stream));
m_specularReflectance = static_cast<Texture *>(manager->getInstance(stream));
m_alpha = static_cast<Texture *>(manager->getInstance(stream)); m_alpha = static_cast<Texture *>(manager->getInstance(stream));
m_intIOR = stream->readFloat(); m_intIOR = stream->readFloat();
m_extIOR = stream->readFloat(); m_extIOR = stream->readFloat();
@ -151,11 +159,13 @@ public:
for (int i=0; i<m_nested->getComponentCount(); ++i) for (int i=0; i<m_nested->getComponentCount(); ++i)
m_components.push_back(m_nested->getType(i) | extraFlags); m_components.push_back(m_nested->getType(i) | extraFlags);
m_components.push_back(EGlossyReflection | EFrontSide | EBackSide); m_components.push_back(EGlossyReflection | EFrontSide | EBackSide
| (m_specularReflectance->isConstant() ? 0 : ESpatiallyVarying));
m_usesRayDifferentials = m_nested->usesRayDifferentials() m_usesRayDifferentials = m_nested->usesRayDifferentials()
|| m_sigmaA->usesRayDifferentials() || m_sigmaA->usesRayDifferentials()
|| m_alpha->usesRayDifferentials(); || m_alpha->usesRayDifferentials()
|| m_specularReflectance->usesRayDifferentials();
/* Compute weights that further steer samples towards /* Compute weights that further steer samples towards
the specular or nested components */ the specular or nested components */
@ -164,6 +174,10 @@ public:
m_specularSamplingWeight = 1.0f / (avgAbsorption + 1.0f); m_specularSamplingWeight = 1.0f / (avgAbsorption + 1.0f);
/* Verify the input parameters and fix them if necessary */
m_specularReflectance = ensureEnergyConservation(
m_specularReflectance, "specularReflectance", 1.0f);
if (!m_roughTransmittance.get()) { if (!m_roughTransmittance.get()) {
/* Load precomputed data used to compute the rough /* Load precomputed data used to compute the rough
transmittance through the dielectric interface */ transmittance through the dielectric interface */
@ -258,7 +272,7 @@ public:
Float value = F * D * G / Float value = F * D * G /
(4.0f * std::abs(Frame::cosTheta(bRec.wi))); (4.0f * std::abs(Frame::cosTheta(bRec.wi)));
result += Spectrum(value); result += m_specularReflectance->getValue(bRec.its) * value;
} }
if (hasNested) { if (hasNested) {
@ -425,6 +439,7 @@ public:
stream->writeUInt((uint32_t) m_distribution.getType()); stream->writeUInt((uint32_t) m_distribution.getType());
manager->serialize(stream, m_nested.get()); manager->serialize(stream, m_nested.get());
manager->serialize(stream, m_sigmaA.get()); manager->serialize(stream, m_sigmaA.get());
manager->serialize(stream, m_specularReflectance.get());
manager->serialize(stream, m_alpha.get()); manager->serialize(stream, m_alpha.get());
stream->writeFloat(m_intIOR); stream->writeFloat(m_intIOR);
stream->writeFloat(m_extIOR); stream->writeFloat(m_extIOR);
@ -455,6 +470,7 @@ public:
<< " distribution = " << m_distribution.toString() << "," << endl << " distribution = " << m_distribution.toString() << "," << endl
<< " alpha = " << indent(m_alpha->toString()) << "," << endl << " alpha = " << indent(m_alpha->toString()) << "," << endl
<< " sigmaA = " << indent(m_sigmaA->toString()) << "," << endl << " sigmaA = " << indent(m_sigmaA->toString()) << "," << endl
<< " specularReflectance = " << indent(m_specularReflectance->toString()) << "," << endl
<< " specularSamplingWeight = " << m_specularSamplingWeight << "," << endl << " specularSamplingWeight = " << m_specularSamplingWeight << "," << endl
<< " diffuseSamplingWeight = " << (1-m_specularSamplingWeight) << "," << endl << " diffuseSamplingWeight = " << (1-m_specularSamplingWeight) << "," << endl
<< " intIOR = " << m_intIOR << "," << endl << " intIOR = " << m_intIOR << "," << endl
@ -472,6 +488,7 @@ private:
ref<RoughTransmittance> m_roughTransmittance; ref<RoughTransmittance> m_roughTransmittance;
ref<Texture> m_sigmaA; ref<Texture> m_sigmaA;
ref<Texture> m_alpha; ref<Texture> m_alpha;
ref<Texture> m_specularReflectance;
ref<BSDF> m_nested; ref<BSDF> m_nested;
Float m_intIOR, m_extIOR; Float m_intIOR, m_extIOR;
Float m_specularSamplingWeight; Float m_specularSamplingWeight;