Added ray-disk intersection and material definition.

disk.cpp

@@ -0,0 +1,17 @@
+#include "disk.hpp"
+
+using glm::dot;
+
+bool Disk::intersect(Ray & r, float & t) const {
+  float _t;
+  vec3 i_pos, i_vec;
+
+  if (Plane::intersect(r, _t)) {
+    i_pos = r.m_origin + (_t * r.m_direction);
+    i_vec = i_pos - m_point;
+    t = _t;
+    return dot(i_vec, i_vec) <= (m_radius * m_radius);
+  }
+
+   return false;
+}