Removed cmath dependency.

directional_light.cpp

@@ -1,5 +1,3 @@
-#include <cmath>
-
 #include <glm/glm.hpp>
 #include <glm/gtc/constants.hpp>
 
@@ -8,12 +6,14 @@
 using glm::pi;
 using glm::reflect;
 using glm::dot;
+using glm::pow;
+using glm::max;
 
 vec3 DirectionalLight::shade(vec3 normal, Ray & r, Material & m) const {
   float n_dot_l, r_dot_l;
   vec3 color, ref;
 
-  n_dot_l = max(dot(normal, m_position), 0.0);
+  n_dot_l = max(dot(normal, m_position), 0.0f);
   color += (m.m_diffuse / pi<float>()) * m_diffuse * n_dot_l;
 
   ref = reflect(m_position, normal);