Add material support

rtweekend.hpp

@@ -33,5 +33,25 @@ inline double clamp(double v, double min, double max)
 #include "ray.hpp"
 #include "vec3.hpp"
 
+struct material;
+
+/* Common data structures */
+
+struct hit_record {
+    point3 p;
+    vec3 normal;
+    std::shared_ptr<material> mat_ptr;
+    double t;
+    bool front_face;
+
+    inline void set_face_normal(const ray& r, const vec3& outward_normal)
+    {
+        front_face = dot(r.direction, outward_normal) < 0;
+        normal = front_face ? outward_normal : -outward_normal;
+    }    
+};
+
+
+
 
 #endif