had forgotten about the phong model, other minor tweaks

src/bsdfs/phong.cpp

@@ -263,6 +263,15 @@ public:
 		manager->serialize(stream, m_exponent.get());
 	}
 
+	Float getRoughness(const Intersection &its, int component) const {
+		Assert(component == 0 || component == 1);
+		/* Find the Beckmann-equivalent roughness */
+		if (component == 0)
+			return std::sqrt(2 / (2+m_exponent->eval(its).average()));
+		else
+			return std::numeric_limits<Float>::infinity();
+	}
+
 	std::string toString() const {
 		std::ostringstream oss;
 		oss << "Phong[" << endl

src/bsdfs/roughcoating.cpp

@@ -440,7 +440,7 @@ public:
 	Float getRoughness(const Intersection &its, int component) const {
 		return component < (int) m_components.size()
 			? m_nested->getRoughness(its, component)
-			: m_alpha->getAverage().average();
+			: m_alpha->eval(its).average();
 	}
 
 	void addChild(const std::string &name, ConfigurableObject *child) {

src/bsdfs/roughplastic.cpp

@@ -505,7 +505,7 @@ public:
 		Assert(component == 0 || component == 1);
 
 		if (component == 0)
-			return m_alpha->getAverage().average();
+			return m_alpha->eval(its).average();
 		else
 			return std::numeric_limits<Float>::infinity();
 	}