Add material support

vec3.hpp

@@ -76,6 +76,13 @@ struct vec3 {
     {
         return vec3(random_double(min, max), random_double(min, max), random_double(min, max));
     }
+
+    // Check if all vector components are near zero
+    bool near_zero() const
+    {
+        double s = 1e-8;
+        return (fabs(x) < s) && (fabs(y) < s) && (fabs(z) < s);
+    }
 };
 
 /* Type aliases */
@@ -175,4 +182,10 @@ vec3 random_in_hemisphere(const vec3& normal)
         return -in_unit_sphere;
 }
 
+// Reflect like a metallic material
+vec3 reflect(const vec3& v, const vec3 n)
+{
+    return v - 2*dot(v,n)*n;
+}
+
 #endif