twosided plugin now supports having a different BRDF on each side

src/bsdfs/twosided.cpp

@@ -25,7 +25,8 @@ MTS_NAMESPACE_BEGIN
 /*!\plugin{twosided}{Two-sided BRDF adapter}
  * \parameters{
  *     \parameter{\Unnamed}{\BSDF}{A nested BRDF that should
- *     be turned into a two-sided scattering model.}
+ *     be turned into a two-sided scattering model. If two BRDFs
+ *     are specified, they will be placed on the front and back side, respectively.}
  * }
  * 
  * \renderings{
@@ -47,7 +48,9 @@ MTS_NAMESPACE_BEGIN
  * bothersome. In that case, this plugin can be used to turn 
  * one-sided scattering models into proper two-sided versions of
  * themselves. The plugin has no parameters other than a required
- * nested BSDF specification.
+ * nested BSDF specification. It is also possible to supply two
+ * different BRDFs that should be placed on the front and back
+ * side, respectively.
  * \vspace{4mm}
  *
  * \begin{xml}[caption=A two-sided diffuse material]
@@ -65,23 +68,36 @@ public:
 
 	TwoSidedBRDF(Stream *stream, InstanceManager *manager) 
 		: BSDF(stream, manager) {
-		m_nestedBRDF = static_cast<BSDF *>(manager->getInstance(stream));
+		m_nestedBRDF[0] = static_cast<BSDF *>(manager->getInstance(stream));
+		m_nestedBRDF[1] = static_cast<BSDF *>(manager->getInstance(stream));
 		configure();
 	}
 
 	void serialize(Stream *stream, InstanceManager *manager) const {
 		BSDF::serialize(stream, manager);
 
-		manager->serialize(stream, m_nestedBRDF.get());
+		manager->serialize(stream, m_nestedBRDF[0].get());
+		manager->serialize(stream, m_nestedBRDF[1].get());
 	}
 
 	void configure() {
-		if (!m_nestedBRDF)
+		if (!m_nestedBRDF[0])
 			Log(EError, "A nested one-sided material is required!");
-		m_usesRayDifferentials = m_nestedBRDF->usesRayDifferentials();
+		if (!m_nestedBRDF[1])
+			m_nestedBRDF[1] = m_nestedBRDF[0];
+
+
+		m_usesRayDifferentials = m_nestedBRDF[0]->usesRayDifferentials()
+			|| m_nestedBRDF[1]->usesRayDifferentials();
+
 		m_components.clear();
-		for (int i=0; i<m_nestedBRDF->getComponentCount(); ++i) 
+
-			m_components.push_back(m_nestedBRDF->getType(i) | EFrontSide | EBackSide);
+		for (int i=0; i<m_nestedBRDF[0]->getComponentCount(); ++i)
+			m_components.push_back((m_nestedBRDF[0]->getType(i) & ~EBackSide) | EFrontSide);
+
+		for (int i=0; i<m_nestedBRDF[1]->getComponentCount(); ++i)
+			m_components.push_back((m_nestedBRDF[1]->getType(i) & ~EFrontSide) | EBackSide);
+
 		BSDF::configure();
 		if (m_combinedType & BSDF::ETransmission)
 			Log(EError, "Only materials without "
@@ -90,36 +106,54 @@ public:
 
 	Spectrum eval(const BSDFQueryRecord &bRec, EMeasure measure) const {
 		BSDFQueryRecord b(bRec);
-		if (Frame::cosTheta(b.wi) < 0) {
+
+		if (Frame::cosTheta(b.wi) > 0) {
+			return m_nestedBRDF[0]->eval(b, measure);
+		} else {
+			if (b.component != -1)
+				b.component -= m_nestedBRDF[0]->getComponentCount();
 			b.wi.z *= -1;
 			b.wo.z *= -1;
+			return m_nestedBRDF[1]->eval(b, measure);
 		}
-		return m_nestedBRDF->eval(b, measure);
 	}
 
 	Float pdf(const BSDFQueryRecord &bRec, EMeasure measure) const {
 		BSDFQueryRecord b(bRec);
-		if (b.wi.z < 0) {
+
+		if (b.wi.z > 0) {
+			return m_nestedBRDF[0]->pdf(b, measure);
+		} else {
+			if (b.component != -1)
+				b.component -= m_nestedBRDF[0]->getComponentCount();
 			b.wi.z *= -1;
 			b.wo.z *= -1;
+			return m_nestedBRDF[1]->pdf(b, measure);
 		}
-		return m_nestedBRDF->pdf(b, measure);
 	}
 
 	Spectrum sample(BSDFQueryRecord &bRec, const Point2 &sample) const {
 		bool flipped = false;
+
 		if (Frame::cosTheta(bRec.wi) < 0) {
 			bRec.wi.z *= -1;
 			flipped = true;
+			if (bRec.component != -1)
+				bRec.component -= m_nestedBRDF[0]->getComponentCount();
 		}
 	
-		Spectrum result = m_nestedBRDF->sample(bRec, sample);
+		Spectrum result = m_nestedBRDF[flipped ? 1 : 0]->sample(bRec, sample);
 
 		if (flipped) {
 			bRec.wi.z *= -1;
-			if (!result.isZero()) 
+			if (bRec.component != -1)
+				bRec.component += m_nestedBRDF[0]->getComponentCount();
+			if (!result.isZero()) {
 				bRec.wo.z *= -1;
+				bRec.sampledComponent += m_nestedBRDF[0]->getComponentCount();
+			}
 		}
+
 		return result;
 	}
 
@@ -128,24 +162,33 @@ public:
 		if (Frame::cosTheta(bRec.wi) < 0) {
 			bRec.wi.z *= -1;
 			flipped = true;
+			if (bRec.component != -1)
+				bRec.component -= m_nestedBRDF[0]->getComponentCount();
 		}
 
-		Spectrum result = m_nestedBRDF->sample(bRec, pdf, sample);
+		Spectrum result = m_nestedBRDF[flipped ? 1 : 0]->sample(bRec, pdf, sample);
 
 		if (flipped) {
 			bRec.wi.z *= -1;
 
-			if (!result.isZero() && pdf != 0)
+			if (bRec.component != -1)
+				bRec.component += m_nestedBRDF[0]->getComponentCount();
+			if (!result.isZero() && pdf != 0) {
 				bRec.wo.z *= -1;
+				bRec.sampledComponent += m_nestedBRDF[0]->getComponentCount();
+			}
 		}
 		return result;
 	}
 
 	void addChild(const std::string &name, ConfigurableObject *child) {
 		if (child->getClass()->derivesFrom(BSDF::m_theClass)) {
-			if (m_nestedBRDF != NULL)
+			if (m_nestedBRDF[0] == NULL)
-				Log(EError, "Only a single nested BRDF can be added!");
+				m_nestedBRDF[0] = static_cast<BSDF *>(child);
-			m_nestedBRDF = static_cast<BSDF *>(child);
+			else if (m_nestedBRDF[1] == NULL)
+				m_nestedBRDF[1] = static_cast<BSDF *>(child);
+			else
+				Log(EError, "No more than two nested BRDFs can be added!");
 		} else {
 			BSDF::addChild(name, child);
 		}
@@ -154,7 +197,8 @@ public:
 	std::string toString() const {
 		std::ostringstream oss;
 		oss << "TwoSided[" << endl
-			<< "  nestedBRDF = " << indent(m_nestedBRDF->toString()) << endl
+			<< "  nestedBRDF[0] = " << indent(m_nestedBRDF[0]->toString()) << "," << endl
+			<< "  nestedBRDF[1] = " << indent(m_nestedBRDF[1]->toString()) << endl
 			<< "]";
 		return oss.str();
 	}
@@ -163,7 +207,7 @@ public:
 
 	MTS_DECLARE_CLASS()
 protected:
-	ref<BSDF> m_nestedBRDF;
+	ref<BSDF> m_nestedBRDF[2];
 };
 
 
@@ -172,21 +216,32 @@ protected:
 class TwoSidedShader : public Shader {
 public:
 	TwoSidedShader(Renderer *renderer, 
-			const BSDF *nestedBRDF) : Shader(renderer, EBSDFShader), 
+			const ref<BSDF> *nestedBRDF) : Shader(renderer, EBSDFShader) {
-			m_nestedBRDF(nestedBRDF) {
+		m_nestedBRDF[0] = nestedBRDF[0].get();
-		m_nestedBRDFShader = renderer->registerShaderForResource(nestedBRDF);
+		m_nestedBRDF[1] = nestedBRDF[1].get();
+
+		m_nestedBRDFShader[0] = renderer->registerShaderForResource(m_nestedBRDF[0]);
+		if (m_nestedBRDF[0] != m_nestedBRDF[1])
+			m_nestedBRDFShader[1] = renderer->registerShaderForResource(m_nestedBRDF[1]);
+		else
+			m_nestedBRDFShader[1] = NULL;
 	}
 
 	bool isComplete() const {
-		return m_nestedBRDFShader.get() != NULL;
+		return m_nestedBRDFShader[0].get() != NULL &&
+		       (m_nestedBRDF[0] == m_nestedBRDF[1] || m_nestedBRDFShader[1].get() != NULL);
 	}
 
 	void putDependencies(std::vector<Shader *> &deps) {
-		deps.push_back(m_nestedBRDFShader.get());
+		deps.push_back(m_nestedBRDFShader[0].get());
+		if (m_nestedBRDF[0] != m_nestedBRDF[1])
+			deps.push_back(m_nestedBRDFShader[1].get());
 	}
 
 	void cleanup(Renderer *renderer) {
-		renderer->unregisterShaderForResource(m_nestedBRDF);
+		renderer->unregisterShaderForResource(m_nestedBRDF[0]);
+		if (m_nestedBRDF[0] != m_nestedBRDF[1])
+			renderer->unregisterShaderForResource(m_nestedBRDF[1]);
 	}
 
 	void generateCode(std::ostringstream &oss,
@@ -195,26 +250,29 @@ public:
 		oss << "vec3 " << evalName << "(vec2 uv, vec3 wi, vec3 wo) {" << endl
 			<< "    if (cosTheta(wi) <= 0.0) {" << endl
 			<< "    	wi.z *= -1; wo.z *= -1;" << endl
+			<< "        return " << (depNames.size() == 2 ? depNames[1] : depNames[0]) << "(uv, wi, wo);" << endl
+			<< "    } else {" << endl
+			<< "        return " << depNames[0] << "(uv, wi, wo);" << endl
 			<< "    }" << endl
-			<< "    return " << depNames[0] << "(uv, wi, wo);" << endl
 			<< "}" << endl
 			<< "vec3 " << evalName << "_diffuse(vec2 uv, vec3 wi, vec3 wo) {" << endl
 			<< "    if (cosTheta(wi) <= 0.0) {" << endl
 			<< "    	wi.z *= -1; wo.z *= -1;" << endl
+			<< "        return " << (depNames.size() == 2 ? depNames[1] : depNames[0]) << "_diffuse(uv, wi, wo);" << endl
+			<< "    } else {" << endl
+			<< "        return " << depNames[0] << "_diffuse(uv, wi, wo);" << endl
 			<< "    }" << endl
-			<< "    return " << depNames[0] << "_diffuse(uv, wi, wo);" << endl
 			<< "}" << endl;
 	}
 
 	MTS_DECLARE_CLASS()
 private:
-	const BSDF *m_nestedBRDF;
+	const BSDF *m_nestedBRDF[2];
-	ref<Shader> m_nestedBRDFShader;
+	ref<Shader> m_nestedBRDFShader[2];
-	bool m_complete;
 };
 
 Shader *TwoSidedBRDF::createShader(Renderer *renderer) const { 
-	return new TwoSidedShader(renderer, m_nestedBRDF.get());
+	return new TwoSidedShader(renderer, m_nestedBRDF);
 }
 
 MTS_IMPLEMENT_CLASS(TwoSidedShader, false, Shader)