got the rough plastic material to work properly again

src/bsdfs/conductor.cpp

@@ -369,7 +369,7 @@ public:
 			<< "}" << endl
 			<< endl
 			<< "vec3 " << evalName << "_diffuse(vec2 uv, vec3 wi, vec3 wo) {" << endl
-			<< "    return " << evalName << "_R0 * 0.31831 * cosTheta(wo);"<< endl
+			<< "    return " << evalName << "_R0 * inv_pi * cosTheta(wo);"<< endl
 			<< "}" << endl;
 	}
 	MTS_DECLARE_CLASS()

src/bsdfs/difftrans.cpp

@@ -171,7 +171,7 @@ public:
 		oss << "vec3 " << evalName << "(vec2 uv, vec3 wi, vec3 wo) {" << endl
 			<< "    if (cosTheta(wi) * cosTheta(wo) >= 0.0)" << endl
 			<< "    	return vec3(0.0);" << endl
-			<< "    return " << depNames[0] << "(uv) * 0.31831 * abs(cosTheta(wo));" << endl
+			<< "    return " << depNames[0] << "(uv) * inv_pi * abs(cosTheta(wo));" << endl
 			<< "}" << endl
 			<< endl
 			<< "vec3 " << evalName << "_diffuse(vec2 uv, vec3 wi, vec3 wo) {" << endl

src/bsdfs/diffuse.cpp

@@ -203,7 +203,7 @@ public:
 		oss << "vec3 " << evalName << "(vec2 uv, vec3 wi, vec3 wo) {" << endl
 			<< "    if (cosTheta(wi) < 0.0 || cosTheta(wo) < 0.0)" << endl
 			<< "    	return vec3(0.0);" << endl
-			<< "    return " << depNames[0] << "(uv) * 0.31831 * cosTheta(wo);" << endl
+			<< "    return " << depNames[0] << "(uv) * inv_pi * cosTheta(wo);" << endl
 			<< "}" << endl
 			<< endl
 			<< "vec3 " << evalName << "_diffuse(vec2 uv, vec3 wi, vec3 wo) {" << endl

src/bsdfs/dipolebrdf.cpp

@@ -291,7 +291,7 @@ public:
 			<< "        reducedAlbedo[i] = reducedSigmaT[i] > 0.0 ? reducedSigmaS[i]/reducedSigmaT[i] : 0.0;" << endl
 			<< "    vec3 rootExp = sqrt((1.0 - reducedAlbedo) * 3.0);" << endl
 			<< "    return (reducedAlbedo * 0.5) * (1+exp(-rootExp*(4.0/3.0 * " << endl
-			<< "      " << evalName << "_A" << "))) * exp(-rootExp) * 0.31831 * cosThetaO;" << endl
+			<< "      " << evalName << "_A" << "))) * exp(-rootExp) * inv_pi * cosThetaO;" << endl
 			<< "}" << endl
 			<< endl
 			<< "vec3 " << evalName << "_diffuse(vec2 uv, vec3 wi, vec3 wo) {" << endl

src/bsdfs/phong.cpp

@@ -333,13 +333,13 @@ public:
 			<< "    if (alpha > 0.0)" << endl 
 			<< "    	specRef = pow(alpha, exponent) * " << endl
 			<< "      (exponent + 2) * 0.15915;" << endl
-			<< "    return (" << depNames[1] << "(uv) * 0.31831" << endl
+			<< "    return (" << depNames[1] << "(uv) * inv_pi" << endl
 			<< "           + " << depNames[2] << "(uv) * specRef) * cosTheta(wo);" << endl
 			<< "}" << endl
 			<< "vec3 " << evalName << "_diffuse(vec2 uv, vec3 wi, vec3 wo) {" << endl
 			<< "    if (wi.z <= 0.0 || wo.z <= 0.0)" << endl
 			<< "    	return vec3(0.0);" << endl
-			<< "    return " << depNames[1] << "(uv) * (0.31831 * cosTheta(wo));" << endl
+			<< "    return " << depNames[1] << "(uv) * (inv_pi * cosTheta(wo));" << endl
 			<< "}" << endl;
 	}
 

src/bsdfs/plastic.cpp

@@ -35,10 +35,10 @@ MTS_NAMESPACE_BEGIN
  *         for physical realism, this parameter should never be touched. \default{1.0}}
  *     \parameter{diffuse\showbreak Reflectance}{\Spectrum\Or\Texture}{Optional
  *         factor used to modulate the diffuse reflection component\default{0.5}}
- *     \parameter{preserveColors}{\Boolean}{
+ *     \parameter{nonlinear}{\Boolean}{
- *         Account for color shifts due to internal scattering? See the main text
+ *         Account for nonlinear color shifts due to internal scattering? See the
- *         for a detailed description.\default{Don't account for them and
+ *         main text for details.\default{Don't account for them and
- *         preserve the colors, i.e. \code{true}}
+ *         preserve the texture colors, i.e. \code{false}}
  *     }
  * }
  *
@@ -75,11 +75,11 @@ MTS_NAMESPACE_BEGIN
  *
  * \renderings{
  *     \medrendering{Diffuse textured rendering}{bsdf_plastic_diffuse}
- *     \medrendering{Plastic, \code{preserveColors=true}}{bsdf_plastic_preserve}
+ *     \medrendering{Plastic, \code{nonlinear=false}}{bsdf_plastic_preserve}
- *     \medrendering{Plastic, \code{preserveColors=false}}{bsdf_plastic_nopreserve}
+ *     \medrendering{Plastic, \code{nonlinear=true}}{bsdf_plastic_nopreserve}
  *     \caption{
- *        \label{fig:plastic-preservecolors}
+ *        \label{fig:plastic-nonlinear}
- *        When asked to do so, this model can account for subtle color shifts due
+ *        When asked to do so, this model can account for subtle nonlinear color shifts due
  *        to internal scattering processes. The above images show a textured
  *        object first rendered using \pluginref{diffuse}, then 
  *        \pluginref{plastic} with the default parameters, and finally using
@@ -92,8 +92,8 @@ MTS_NAMESPACE_BEGIN
  * base layer on its own---in particular, the material color will tend to shift towards 
  * darker colors with higher saturation. Since this can be counter-intuitive when 
  * using bitmap textures, these color shifts are disabled by default. Specify
- * the parameter \code{preserveColors=false} to enable them. 
+ * the parameter \code{nonlinear=true} to enable them. 
- * \figref{plastic-preservecolors} illustrates this effect.
+ * \figref{plastic-nonlinear} illustrates this effect.
  *
  * Similar to the \pluginref{dielectric} plugin, this model allows to specify
  * IOR values either numerically, or based on a list of known materials (see 
@@ -130,7 +130,7 @@ public:
 		m_diffuseReflectance = new ConstantSpectrumTexture(
 			props.getSpectrum("diffuseReflectance", Spectrum(0.5f)));
 
-		m_preserveColors = props.getBoolean("preserveColors", true);
+		m_nonlinear = props.getBoolean("nonlinear", false);
 
 		m_specularSamplingWeight = 0.0f;
 	}
@@ -139,7 +139,7 @@ public:
 			: BSDF(stream, manager) {
 		m_intIOR = stream->readFloat();
 		m_extIOR = stream->readFloat();
-		m_preserveColors = stream->readBool();
+		m_nonlinear = stream->readBool();
 		m_specularReflectance = static_cast<Texture *>(manager->getInstance(stream));
 		m_diffuseReflectance = static_cast<Texture *>(manager->getInstance(stream));
 		configure();
@@ -153,7 +153,8 @@ public:
 			m_diffuseReflectance, "diffuseReflectance", 1.0f);
 
 		/* Numerically approximate the diffuse Fresnel reflectance */
-		m_fdr = fresnelDiffuseReflectance(m_extIOR / m_intIOR, false);
+		m_fdrInt = fresnelDiffuseReflectance(m_extIOR / m_intIOR, false);
+		m_fdrExt = fresnelDiffuseReflectance(m_intIOR / m_extIOR, false);
 
 		/* Compute weights that further steer samples towards
 		   the specular or diffuse components */
@@ -162,8 +163,8 @@ public:
 
 		m_specularSamplingWeight = sAvg / (dAvg + sAvg);
 		
-		Float eta = m_extIOR / m_intIOR;
+		Float invEta = m_extIOR / m_intIOR;
-		m_eta2 = eta*eta;
+		m_invEta2 = invEta*invEta;
 
 		m_usesRayDifferentials = 
 			m_specularReflectance->usesRayDifferentials() ||
@@ -178,9 +179,8 @@ public:
 		BSDF::configure();
 	}
 
-
 	Spectrum getDiffuseReflectance(const Intersection &its) const {
-		return m_diffuseReflectance->getValue(its);
+		return m_diffuseReflectance->getValue(its) * (1-m_fdrExt);
 	}
 
 	void serialize(Stream *stream, InstanceManager *manager) const {
@@ -188,7 +188,7 @@ public:
 
 		stream->writeFloat(m_intIOR);
 		stream->writeFloat(m_extIOR);
-		stream->writeBool(m_preserveColors);
+		stream->writeBool(m_nonlinear);
 		manager->serialize(stream, m_specularReflectance.get());
 		manager->serialize(stream, m_diffuseReflectance.get());
 	}
@@ -232,11 +232,11 @@ public:
 			Float Fr2 = fresnel(Frame::cosTheta(bRec.wo), m_extIOR, m_intIOR);
 
 			Spectrum diff = m_diffuseReflectance->getValue(bRec.its);
-			if (m_preserveColors)
+			if (m_nonlinear)
-				diff /= 1 - m_fdr;
+				diff /= Spectrum(1) - diff * m_fdrInt;
 			else
-				diff /= Spectrum(1) - diff * m_fdr;
+				diff /= 1 - m_fdrInt;
-			return diff * (INV_PI * Frame::cosTheta(bRec.wo) * m_eta2 * (1-Fr) * (1-Fr2));
+			return diff * (INV_PI * Frame::cosTheta(bRec.wo) * m_invEta2 * (1-Fr) * (1-Fr2));
 		}
 
 		return Spectrum(0.0f);
@@ -305,12 +305,12 @@ public:
 				Float Fr2 = fresnel(Frame::cosTheta(bRec.wo), m_extIOR, m_intIOR);
 
 				Spectrum diff = m_diffuseReflectance->getValue(bRec.its);
-				if (m_preserveColors)
+				if (m_nonlinear)
-					diff /= 1 - m_fdr;
+					diff /= Spectrum(1) - m_fdrInt*diff;
 				else
-					diff /= Spectrum(1) - m_fdr*diff;
+					diff /= 1 - m_fdrInt;
 
-				return diff * (m_eta2 * (1-Fr) * (1-Fr2) / (1-probSpecular));
+				return diff * (m_invEta2 * (1-Fr) * (1-Fr2) / (1-probSpecular));
 			}
 		} else if (hasSpecular) {
 			bRec.sampledComponent = 0;
@@ -324,12 +324,12 @@ public:
 			bRec.sampledType = EDiffuseReflection;
 
 			Spectrum diff = m_diffuseReflectance->getValue(bRec.its);
-			if (m_preserveColors)
+			if (m_nonlinear)
-				diff /= 1 - m_fdr;
+				diff /= Spectrum(1) - diff*m_fdrInt;
 			else
-				diff /= Spectrum(1) - m_fdr*diff;
+				diff /= 1 - m_fdrInt;
 
-			return diff * (m_eta2 * (1-Fr) * (1-Fr2));
+			return diff * (m_invEta2 * (1-Fr) * (1-Fr2));
 		}
 	}
 
@@ -367,14 +367,14 @@ public:
 				Float Fr2 = fresnel(Frame::cosTheta(bRec.wo), m_extIOR, m_intIOR);
 
 				Spectrum diff = m_diffuseReflectance->getValue(bRec.its);
-				if (m_preserveColors)
+				if (m_nonlinear)
-					diff /= 1 - m_fdr;
+					diff /= Spectrum(1) - diff*m_fdrInt;
 				else
-					diff /= Spectrum(1) - m_fdr*diff;
+					diff /= 1 - m_fdrInt;
 
 				pdf = (1-probSpecular) * Frame::cosTheta(bRec.wo) * INV_PI;
 	
-				return diff * (m_eta2 * (1-Fr) * (1-Fr2) / (1-probSpecular));
+				return diff * (m_invEta2 * (1-Fr) * (1-Fr2) / (1-probSpecular));
 			}
 		} else if (hasSpecular) {
 			bRec.sampledComponent = 0;
@@ -391,12 +391,12 @@ public:
 			pdf = Frame::cosTheta(bRec.wo) * INV_PI;
 
 			Spectrum diff = m_diffuseReflectance->getValue(bRec.its);
-			if (m_preserveColors)
+			if (m_nonlinear)
-				diff /= 1 - m_fdr;
+				diff /= Spectrum(1) - diff*m_fdrInt;
 			else
-				diff /= Spectrum(1) - m_fdr*diff;
+				diff /= 1 - m_fdrInt;
 
-			return diff * (m_eta2 * (1-Fr) * (1-Fr2));
+			return diff * (m_invEta2 * (1-Fr) * (1-Fr2));
 		}
 	}
 
@@ -410,21 +410,23 @@ public:
 			<< "  diffuseReflectance = " << indent(m_diffuseReflectance->toString()) << "," << endl
 			<< "  specularSamplingWeight = " << m_specularSamplingWeight << "," << endl
 			<< "  diffuseSamplingWeight = " << (1-m_specularSamplingWeight) << "," << endl
-			<< "  preserveColors = " << m_preserveColors << "," << endl
+			<< "  nonlinear = " << m_nonlinear << "," << endl
 			<< "  intIOR = " << m_intIOR << "," << endl 
 			<< "  extIOR = " << m_extIOR << "," << endl
-			<< "  fdr = " << m_fdr << endl
+			<< "  fdrInt = " << m_fdrInt << "," << endl
+			<< "  fdrExt = " << m_fdrExt << endl
 			<< "]";
 		return oss.str();
 	}
 
 	MTS_DECLARE_CLASS()
 private:
-	Float m_intIOR, m_extIOR, m_fdr, m_eta2;
+	Float m_intIOR, m_extIOR;
+	Float m_fdrInt, m_fdrExt, m_invEta2;
 	ref<Texture> m_diffuseReflectance;
 	ref<Texture> m_specularReflectance;
 	Float m_specularSamplingWeight;
-	bool m_preserveColors;
+	bool m_nonlinear;
 };
 
 /**
@@ -512,12 +514,12 @@ public:
 			<< "    float G = " << evalName << "_G(H, wi, wo);" << endl
 			<< "    float F = " << evalName << "_schlick(1-dot(wi, H));" << endl
 			<< "    return specRef    * (F * D * G / (4*cosTheta(wi))) + " << endl
-			<< "           diffuseRef * ((1-F) * cosTheta(wo) * 0.31831);" << endl
+			<< "           diffuseRef * ((1-F) * cosTheta(wo) * inv_pi);" << endl
 			<< "}" << endl
 			<< endl
 			<< "vec3 " << evalName << "_diffuse(vec2 uv, vec3 wi, vec3 wo) {" << endl
 			<< "    vec3 diffuseRef = " << depNames[1] << "(uv);" << endl
-			<< "    return diffuseRef * 0.31831 * cosTheta(wo);"<< endl
+			<< "    return diffuseRef * inv_pi * cosTheta(wo);"<< endl
 			<< "}" << endl;
 	}
 	MTS_DECLARE_CLASS()

src/bsdfs/roughconductor.cpp

@@ -517,7 +517,7 @@ public:
 			<< "}" << endl
 			<< endl
 			<< "vec3 " << evalName << "_diffuse(vec2 uv, vec3 wi, vec3 wo) {" << endl
-			<< "    return " << evalName << "_R0 * 0.31831 * cosTheta(wo);"<< endl
+			<< "    return " << evalName << "_R0 * inv_pi * cosTheta(wo);"<< endl
 			<< "}" << endl;
 	}
 	MTS_DECLARE_CLASS()

src/bsdfs/roughdiffuse.cpp

@@ -333,13 +333,13 @@ public:
 			<< "        tanBeta = sinTheta(wo) / cosTheta(wo);" << endl
 			<< "    }" << endl
 			<< "    float value = A + B * maxCos * sinAlpha * tanBeta;" << endl
-			<< "    return " << depNames[0] << "(uv) * 0.31831 * cosTheta(wo) * value;" << endl
+			<< "    return " << depNames[0] << "(uv) * inv_pi * cosTheta(wo) * value;" << endl
 			<< "}" << endl
 			<< endl
 			<< "vec3 " << evalName << "_diffuse(vec2 uv, vec3 wi, vec3 wo) {" << endl
 			<< "    if (cosTheta(wi) <= 0.0 || cosTheta(wo) <= 0.0)" << endl
 			<< "    	return vec3(0.0);" << endl
-			<< "    return " << depNames[0] << "(uv) * 0.31831 * cosTheta(wo);" << endl
+			<< "    return " << depNames[0] << "(uv) * inv_pi * cosTheta(wo);" << endl
 			<< "}" << endl;
 	}
 

src/bsdfs/roughplastic.cpp

@@ -42,7 +42,7 @@ MTS_NAMESPACE_BEGIN
  *              Due to the underlying microfacet theory, 
  *              the use of this distribution here leads to more realistic 
  *              behavior than the separately available \pluginref{phong} plugin.
- *              \vspace{-4mm}
+ *              \vspace{-3mm}
  *       \end{enumerate}
  *     }
  *     \parameter{alpha}{\Float}{
@@ -60,26 +60,22 @@ MTS_NAMESPACE_BEGIN
  *         that for physical realism, this parameter should never be touched. \default{1.0}}
  *     \parameter{diffuse\showbreak Reflectance}{\Spectrum\Or\Texture}{Optional
  *         factor used to modulate the diffuse reflection component\default{0.5}}
- *     \parameter{preserveColors}{\Boolean}{
+ *     \parameter{nonlinear}{\Boolean}{
- *         Account for color shifts due to internal scattering? See the main text
+ *         Account for nonlinear color shifts due to internal scattering? See the
- *         for a detailed description.\default{Don't account for them and
+ *         main text for details.\default{Don't account for them and
- *         preserve the colors, i.e. \code{true}}
+ *         preserve the texture colors, i.e. \code{false}}
- * }\vspace{-1mm}
+ *     }
+ * }
  * \renderings{
  *     \rendering{Beckmann, $\alpha=0.1$}{bsdf_roughplastic_beckmann}
  *     \rendering{GGX, $\alpha=0.3$}{bsdf_roughplastic_ggx}
- * }\vspace{-1mm}
+ * }
  *
  * This plugin implements a realistic microfacet scattering model for rendering
  * rough dielectric materials with internal scattering, such as plastic. It can 
  * be interpreted as a fancy version of the Cook-Torrance model and should be 
  * preferred over empirical models like \pluginref{phong} and \pluginref{ward} 
  * when possible.
- * \renderings{
- *     \setcounter{subfigure}{2}
- *     \rendering{Beckmann, $\alpha=0.05$, diffuseReflectance=0}
- *         {bsdf_roughplastic_beckmann_lacquer}
- * }
  *
  * Microfacet theory describes rough surfaces as an arrangement of unresolved and 
  * ideally specular facets, whose normal directions are given by a specially
@@ -112,6 +108,12 @@ MTS_NAMESPACE_BEGIN
  * which describe a white polypropylene plastic material with a light amount
  * of roughness modeled using the Beckmann distribution.
  *
+ * \renderings{
+ *     \setcounter{subfigure}{2}
+ *     \rendering{Beckmann, $\alpha=0.05$, diffuseReflectance=0}
+ *         {bsdf_roughplastic_beckmann_lacquer}
+ * }
+ *
  * To get an intuition about the effect of the surface roughness
  * parameter $\alpha$, consider the following approximate differentiation: 
  * a value of $\alpha=0.001-0.01$ corresponds to a material 
@@ -119,14 +121,15 @@ MTS_NAMESPACE_BEGIN
  * otherwise smooth surface finish, $\alpha=0.1$ is relatively rough,
  * and $\alpha=0.3-0.7$ is \emph{extremely} rough (e.g. an etched or ground
  * finish). Values significantly above that are probably not too realistic.
-*
+ *
  * When rendering with the Phong microfacet 
  * distributions, a conversion is used to turn the specified 
  * $\alpha$ roughness value into the Phong exponent.
  * This is done in a way, such that the different 
  * distributions all produce a similar appearance for 
  * the same value of $\alpha$.
- * \begin{xml}[caption={A material definition for rough, black laquer.}, label=lst:roughplastic-lacquer]
+ * \begin{xml}[caption={A material definition for rough, black laquer.}, 
+ *    label=lst:roughplastic-lacquer]
  * <bsdf type="roughplastic">
  *     <string name="distribution" value="beckmann"/>
  *     <float name="alpha" value="0.05"/>
@@ -162,7 +165,7 @@ public:
 			Log(EError, "The 'roughplastic' plugin currently does not support "
 				"anisotropic microfacet distributions!");
 
-		m_preserveColors = props.getBoolean("preserveColors", true);
+		m_nonlinear = props.getBoolean("nonlinear", true);
 
 		m_alpha = new ConstantFloatTexture(
 			props.getFloat("alpha", 0.1f));
@@ -180,7 +183,7 @@ public:
 		m_alpha = static_cast<Texture *>(manager->getInstance(stream));
 		m_intIOR = stream->readFloat();
 		m_extIOR = stream->readFloat();
-		m_preserveColors = stream->readBool();
+		m_nonlinear = stream->readBool();
 
 		configure();
 	}
@@ -210,23 +213,26 @@ public:
 		m_specularSamplingWeight = sAvg / (dAvg + sAvg);
 			
 		Float eta = m_intIOR / m_extIOR;
+		m_invEta2 = 1.0f / (eta*eta);
 
-		if (!m_roughTransmittance.get()) {
+		if (!m_externalRoughTransmittance.get()) {
 			/* Load precomputed data used to compute the rough
 			   transmittance through the dielectric interface */
-			m_roughTransmittance = new RoughTransmittance(
+			m_externalRoughTransmittance = new RoughTransmittance(
 				m_distribution.getType());
 
-			m_roughTransmittance->checkEta(eta);
+			m_externalRoughTransmittance->checkEta(eta);
-			m_roughTransmittance->checkAlpha(m_alpha->getMinimum().average());
+			m_externalRoughTransmittance->checkAlpha(m_alpha->getMinimum().average());
-			m_roughTransmittance->checkAlpha(m_alpha->getMaximum().average());
+			m_externalRoughTransmittance->checkAlpha(m_alpha->getMaximum().average());
 			
 			/* Reduce the rough transmittance data to a 2D slice */
-			m_roughTransmittance->setEta(eta);
+			m_internalRoughTransmittance = m_externalRoughTransmittance->clone();
+			m_externalRoughTransmittance->setEta(eta);
+			m_internalRoughTransmittance->setEta(1/eta);
 
 			/* If possible, even reduce it to a 1D slice */
 			if (constAlpha) 
-				m_roughTransmittance->setAlpha(
+				m_externalRoughTransmittance->setAlpha(
 					m_alpha->getValue(Intersection()).average());
 		}
 
@@ -238,7 +244,11 @@ public:
 	}
 
 	Spectrum getDiffuseReflectance(const Intersection &its) const {
-		return m_diffuseReflectance->getValue(its);
+		/* Evaluate the roughness texture */
+		Float alpha = m_alpha->getValue(its).average();
+		Float Ftr = m_externalRoughTransmittance->evalDiffuse(alpha);
+
+		return m_diffuseReflectance->getValue(its) * Ftr;
 	}
 
 	/// Helper function: reflect \c wi with respect to a given surface normal
@@ -285,16 +295,16 @@ public:
 
 		if (hasDiffuse) { 
 			Spectrum diff = m_diffuseReflectance->getValue(bRec.its);
-			Float T12 = m_roughTransmittance->eval(Frame::cosTheta(bRec.wi), alpha);
+			Float T12 = m_externalRoughTransmittance->eval(Frame::cosTheta(bRec.wi), alpha);
-			Float T21 = m_roughTransmittance->eval(Frame::cosTheta(bRec.wo), alpha);
+			Float T21 = m_externalRoughTransmittance->eval(Frame::cosTheta(bRec.wo), alpha);
-			Float Fdr = 1-m_roughTransmittance->evalDiffuse(alpha);
+			Float Fdr = 1-m_internalRoughTransmittance->evalDiffuse(alpha);
 
-			if (m_preserveColors)
+			if (m_nonlinear)
-				diff /= 1-Fdr;
-			else
 				diff /= Spectrum(1.0f) - diff * Fdr;
+			else
+				diff /= 1-Fdr;
 
-			result += diff * (INV_PI * Frame::cosTheta(bRec.wo) * T12 * T21);
+			result += diff * (INV_PI * Frame::cosTheta(bRec.wo) * T12 * T21 * m_invEta2);
 		}
 
 		return result;
@@ -322,7 +332,7 @@ public:
 		Float probDiffuse, probSpecular;
 		if (hasSpecular && hasDiffuse) {
 			/* Find the probability of sampling the specular component */
-			probSpecular = 1-m_roughTransmittance->eval(Frame::cosTheta(bRec.wi), alpha);
+			probSpecular = 1-m_externalRoughTransmittance->eval(Frame::cosTheta(bRec.wi), alpha);
 
 			/* Reallocate samples */
 			probSpecular = (probSpecular*m_specularSamplingWeight) /
@@ -370,7 +380,7 @@ public:
 		Float probSpecular;
 		if (hasSpecular && hasDiffuse) {
 			/* Find the probability of sampling the specular component */
-			probSpecular = 1 - m_roughTransmittance->eval(Frame::cosTheta(bRec.wi), alpha);
+			probSpecular = 1 - m_externalRoughTransmittance->eval(Frame::cosTheta(bRec.wi), alpha);
 
 			/* Reallocate samples */
 			probSpecular = (probSpecular*m_specularSamplingWeight) /
@@ -424,7 +434,7 @@ public:
 		manager->serialize(stream, m_alpha.get());
 		stream->writeFloat(m_intIOR);
 		stream->writeFloat(m_extIOR);
-		stream->writeBool(m_preserveColors);
+		stream->writeBool(m_nonlinear);
 	}
 
 	void addChild(const std::string &name, ConfigurableObject *child) {
@@ -452,7 +462,7 @@ public:
 			<< "  diffuseReflectance = " << indent(m_diffuseReflectance->toString()) << "," << endl
 			<< "  specularSamplingWeight = " << m_specularSamplingWeight << "," << endl
 			<< "  diffuseSamplingWeight = " << (1-m_specularSamplingWeight) << "," << endl
-			<< "  preserveColors = " << m_preserveColors << "," << endl
+			<< "  nonlinear = " << m_nonlinear << "," << endl
 			<< "  intIOR = " << m_intIOR << "," << endl
 			<< "  extIOR = " << m_extIOR << endl
 			<< "]";
@@ -464,13 +474,14 @@ public:
 	MTS_DECLARE_CLASS()
 private:
 	MicrofacetDistribution m_distribution;
-	ref<RoughTransmittance> m_roughTransmittance;
+	ref<RoughTransmittance> m_externalRoughTransmittance;
+	ref<RoughTransmittance> m_internalRoughTransmittance;
 	ref<Texture> m_diffuseReflectance;
 	ref<Texture> m_specularReflectance;
 	ref<Texture> m_alpha;
-	Float m_intIOR, m_extIOR;
+	Float m_intIOR, m_extIOR, m_invEta2;
 	Float m_specularSamplingWeight;
-	bool m_preserveColors;
+	bool m_nonlinear;
 };
 
 /**
@@ -520,7 +531,7 @@ public:
 	}
 
 	void bind(GPUProgram *program, const std::vector<int> &parameterIDs, int &textureUnitOffset) const {
-		program->setParameter(parameterIDs[1], m_R0);
+		program->setParameter(parameterIDs[0], m_R0);
 	}
 
 	void generateCode(std::ostringstream &oss,
@@ -559,17 +570,18 @@ public:
 			<< "    vec3 H = normalize(wi + wo);" << endl
 			<< "    vec3 specRef = " << depNames[0] << "(uv);" << endl
 			<< "    vec3 diffuseRef = " << depNames[1] << "(uv);" << endl
-			<< "    float alpha = " << depNames[2] << "(uv)[0];" << endl
+//			<< "    float alpha = max(0.2, " << depNames[2] << "(uv)[0]);" << endl
+			<< "    float alpha = 0.4;" << endl
 			<< "    float D = " << evalName << "_D(H, alpha)" << ";" << endl
 			<< "    float G = " << evalName << "_G(H, wi, wo);" << endl
 			<< "    float F = " << evalName << "_schlick(1-dot(wi, H));" << endl
 			<< "    return specRef    * (F * D * G / (4*cosTheta(wi))) + " << endl
-			<< "           diffuseRef * ((1-F) * cosTheta(wo) * 0.31831);" << endl
+			<< "           diffuseRef * ((1-F) * cosTheta(wo) * inv_pi);" << endl
 			<< "}" << endl
 			<< endl
 			<< "vec3 " << evalName << "_diffuse(vec2 uv, vec3 wi, vec3 wo) {" << endl
 			<< "    vec3 diffuseRef = " << depNames[1] << "(uv);" << endl
-			<< "    return diffuseRef * 0.31831 * cosTheta(wo);"<< endl
+			<< "    return diffuseRef * inv_pi * cosTheta(wo);"<< endl
 			<< "}" << endl;
 	}
 	MTS_DECLARE_CLASS()

src/bsdfs/rtrans.h

@@ -102,17 +102,17 @@ public:
 		m_alphaSamples = fstream->readSize();
 		m_thetaSamples = fstream->readSize();
 		
-		size_t transSize = 2 * m_etaSamples * m_alphaSamples * m_thetaSamples;
+		m_transSize = 2 * m_etaSamples * m_alphaSamples * m_thetaSamples;
-		size_t diffTransSize = 2 * m_etaSamples * m_alphaSamples;
+		m_diffTransSize = 2 * m_etaSamples * m_alphaSamples;
 
 		SLog(EDebug, "Loading " SIZE_T_FMT "x" SIZE_T_FMT "x" SIZE_T_FMT 
 			" (%s) rough transmittance samples from \"%s\"", 2*m_etaSamples,
 			m_alphaSamples, m_thetaSamples, 
-			memString((transSize + diffTransSize) * sizeof(float)).c_str(),
+			memString((m_transSize + m_diffTransSize) * sizeof(float)).c_str(),
 			sourceFile.file_string().c_str());
 
-		m_trans = new Float[transSize];
+		m_trans = new Float[m_transSize];
-		m_diffTrans = new Float[diffTransSize];
+		m_diffTrans = new Float[m_diffTransSize];
 		m_etaFixed = false;
 		m_alphaFixed = false;
 
@@ -125,8 +125,8 @@ public:
 			"[%.4f, %.1f] and roughness range [%.4f, %.1f]",  m_etaMin,
 			m_etaMax, m_alphaMin, m_alphaMax);
 
-		float *temp = new float[transSize + diffTransSize];
+		float *temp = new float[m_transSize + m_diffTransSize];
-		fstream->readSingleArray(temp, transSize + diffTransSize);
+		fstream->readSingleArray(temp, m_transSize + m_diffTransSize);
 
 		float *ptr = temp;
 		size_t fdrEntry = 0, dataEntry = 0;
@@ -282,11 +282,11 @@ public:
 		if (m_etaFixed)
 			return;
 
-		size_t transSize = m_alphaSamples * m_thetaSamples;
+		m_transSize = m_alphaSamples * m_thetaSamples;
-		size_t diffTransSize = m_alphaSamples;
+		m_diffTransSize = m_alphaSamples;
 
 		SLog(EDebug, "Reducing dimension from 3D to 2D (%s), eta = %f", 
-			memString((transSize + diffTransSize) * sizeof(Float)).c_str(), eta);
+			memString((m_transSize + m_diffTransSize) * sizeof(Float)).c_str(), eta);
 
 		Float *trans = m_trans,
 			  *diffTrans = m_diffTrans;
@@ -305,8 +305,8 @@ public:
 		Float warpedEta = std::pow((eta - m_etaMin) 
 				/ (m_etaMax-m_etaMin), 0.25f);
 
-		Float *newTrans = new Float[transSize];
+		Float *newTrans = new Float[m_transSize];
-		Float *newDiffTrans = new Float[diffTransSize];
+		Float *newDiffTrans = new Float[m_diffTransSize];
 
 		Float dAlpha = 1.0f / (m_alphaSamples - 1),
 			  dTheta = 1.0f / (m_thetaSamples - 1);
@@ -344,17 +344,17 @@ public:
 		if (m_alphaFixed)
 			return;
 
-		size_t transSize = m_thetaSamples;
+		m_transSize = m_thetaSamples;
-		size_t diffTransSize = 1;
+		m_diffTransSize = 1;
 
 		SLog(EDebug, "Reducing dimension from 2D to 1D (%s), alpha = %f", 
-			memString((transSize + diffTransSize) * sizeof(Float)).c_str(), alpha);
+			memString((m_transSize + m_diffTransSize) * sizeof(Float)).c_str(), alpha);
 
 		Float warpedAlpha = std::pow((alpha - m_alphaMin) 
 				/ (m_alphaMax-m_alphaMin), 0.25f);
 
-		Float *newTrans = new Float[transSize];
+		Float *newTrans = new Float[m_transSize];
-		Float *newDiffTrans = new Float[diffTransSize];
+		Float *newDiffTrans = new Float[m_diffTransSize];
 
 		Float dTheta = 1.0f / (m_thetaSamples - 1);
 
@@ -388,12 +388,35 @@ public:
 		if (eta < 1)
 			eta = 1/eta;
 		if (eta < m_etaMin || eta > m_etaMax) 
-			SLog(EError, "Error: the requested index of refraction eta=%f is"
+			SLog(EError, "Error: the requested relative index of refraction "
-				" outside of the supported range [%f, %f]! Please update your "
+				"eta=%f is outside of the supported range [%f, %f]! Please "
-				" scene so that it uses realistic IOR values.", eta, 
+				"update your  scene so that it uses realistic IOR values.", 
-				m_etaMin, m_etaMax);
+				eta, m_etaMin, m_etaMax);
 	}
 
+	/// Create a deep copy of the current instance
+	ref<RoughTransmittance> clone() const {
+		RoughTransmittance *result = new RoughTransmittance();
+		result->m_name = m_name;
+		result->m_etaSamples = m_etaSamples;
+		result->m_alphaSamples = m_alphaSamples;
+		result->m_thetaSamples = m_thetaSamples;
+		result->m_etaFixed = m_etaFixed;
+		result->m_alphaFixed = m_alphaFixed;
+		result->m_etaMin = m_etaMin;
+		result->m_etaMax = m_etaMax;
+		result->m_alphaMin = m_alphaMin;
+		result->m_alphaMax = m_alphaMax;
+		result->m_transSize = m_transSize;
+		result->m_diffTransSize = m_diffTransSize;
+		result->m_trans = new Float[m_transSize];
+		result->m_diffTrans = new Float[m_diffTransSize];
+		memcpy(result->m_trans, m_trans, m_transSize * sizeof(Float));
+		memcpy(result->m_diffTrans, m_diffTrans, m_diffTransSize * sizeof(Float));
+		return result;
+	}
+protected:
+	inline RoughTransmittance() { }
 protected:
 	std::string m_name;
 	size_t m_etaSamples;
@@ -403,6 +426,8 @@ protected:
 	bool m_alphaFixed;
 	Float m_etaMin, m_etaMax;
 	Float m_alphaMin, m_alphaMax;
+	size_t m_transSize;
+	size_t m_diffTransSize;
 	Float *m_trans, *m_diffTrans;
 };
 

src/bsdfs/ward.cpp

@@ -449,13 +449,13 @@ public:
 			<< "    float factor2 = H.x / alphaU, factor3 = H.y / alphaV;" << endl
 			<< "    float exponent = -(factor2*factor2 + factor3*factor3)/(H.z*H.z);" << endl
 			<< "    float specRef = factor1 * exp(exponent);" << endl 
-			<< "    return (" << depNames[0] << "(uv) * 0.31831" << endl
+			<< "    return (" << depNames[0] << "(uv) * inv_pi" << endl
 			<< "           + " << depNames[1] << "(uv) * specRef) * cosTheta(wo);" << endl
 			<< "}" << endl
 			<< "vec3 " << evalName << "_diffuse(vec2 uv, vec3 wi, vec3 wo) {" << endl
 			<< "    if (wi.z <= 0.0 || wo.z <= 0.0)" << endl
 			<< "    	return vec3(0.0);" << endl
-			<< "    return " << depNames[0] << "(uv) * (0.31831 * cosTheta(wo));" << endl
+			<< "    return " << depNames[0] << "(uv) * (inv_pi * cosTheta(wo));" << endl
 			<< "}" << endl;
 	}
 

src/libhw/vpl.cpp

@@ -503,6 +503,7 @@ void VPLShaderManager::configure(const VPL &vpl, const BSDF *bsdf,
 			<< "float sinPhi(vec3 v) { return v.y/sinTheta(v); }" << endl
 			<< "float cosPhi(vec3 v) { return v.x/sinTheta(v); }" << endl
 			<< "const float pi = 3.141592653589;" << endl
+			<< "const float inv_pi = 0.318309886183791;" << endl
 			<< endl;
 
 		std::string vplEvalName, bsdfEvalName, lumEvalName;