Added presentations from EVI 2017

EVI - 2017/EVI 21/EVIray/brdf.hpp

@@ -0,0 +1,19 @@
+#pragma once
+#ifndef BRDF_HPP
+#define BRDF_HPP
+
+#include <glm/vec3.hpp>
+
+#include "ray.hpp"
+
+using glm::vec3;
+
+class BRDF {
+public:
+  virtual ~BRDF() { }
+  
+  virtual vec3 diffuse(vec3 light_dir, vec3 surface_normal, Ray & incident_ray, vec3 intersection_point, vec3 light_diff_color) const = 0;
+  virtual vec3 specular(vec3 light_dir, vec3 surface_normal, Ray & incident_ray, vec3 intersection_point, vec3 light_spec_color, float shininess) const = 0;
+};
+
+#endif