Refactor materials, reflective material still not done

RayTracer/material/BackgroundMaterial.cpp

 #include "BackgroundMaterial.h"
 
+#include <cassert>
+
 #include "texture/Constant.h"
 
 namespace material {
@@ -44,4 +46,10 @@ float BackgroundMaterial::calculateLightMultiplier(const util::Vec3& d_in,
 	// Background should not be able to receive any light
 	return 0;
 }
+float BackgroundMaterial::brdf_pdf(const util::Vec3& d_out,
+                                   const util::Vec3& n) const {
+	// Background can not scatter so this is fine and will never be used
+	assert(false);
+	return 0;
+}
 }  // namespace material
\ No newline at end of file

RayTracer/material/BackgroundMaterial.h

@@ -21,6 +21,8 @@ class BackgroundMaterial : public Material {
 	float calculateLightMultiplier(const util::Vec3& d_in,
 	                               const util::Vec3& d_out,
 	                               const util::Vec3& n) const override;
+
+	float brdf_pdf(const util::Vec3& d_out, const util::Vec3& n) const override;
 	std::optional<float> emission_pdf(float u, float v) const override;
 
    private:

RayTracer/material/DiffuseMaterial.cpp

@@ -60,4 +60,11 @@ float DiffuseMaterial::calculateLightMultiplier(const util::Vec3& d_in,
                                                 const util::Vec3& n) const {
 	return M_1_PI;
 }
+
+float DiffuseMaterial::brdf_pdf(const util::Vec3& d_out,
+                                const util::Vec3& n) const {
+	auto dot = util::dot(n, d_out.normalize());
+	dot = std::max<float>(dot, 0);
+	return dot * M_1_PI;
+}
 }  // namespace material
\ No newline at end of file

RayTracer/material/DiffuseMaterial.h

@@ -24,6 +24,7 @@ class DiffuseMaterial : public Material {
 	float calculateLightMultiplier(const util::Vec3& d_in,
 	                               const util::Vec3& d_out,
 	                               const util::Vec3& n) const override;
+	float brdf_pdf(const util::Vec3& d_out, const util::Vec3& n) const override;
 	std::optional<float> emission_pdf(float u, float v) const override;
 
    private:

RayTracer/material/ReflectiveMaterial.cpp

@@ -58,4 +58,10 @@ float ReflectiveMaterial::calculateLightMultiplier(const util::Vec3& d_in,
 
 	return std::cos(std::min<float>(theta * 3, M_PI / 2));
 }
+
+float ReflectiveMaterial::brdf_pdf(const util::Vec3& d_out,
+                                   const util::Vec3& n) const {
+	// This is gonna be a problem, because this material can scatter
+	return 0;
+}
 }  // namespace material
\ No newline at end of file

RayTracer/material/ReflectiveMaterial.h

@@ -22,6 +22,7 @@ class ReflectiveMaterial : public Material {
 	float calculateLightMultiplier(const util::Vec3& d_in,
 	                               const util::Vec3& d_out,
 	                               const util::Vec3& n) const override;
+	float brdf_pdf(const util::Vec3& d_out, const util::Vec3& n) const override;
 
    private:
 	std::shared_ptr<util::Sampler> albedo_texture;