Started scene reader. Added libjson-spirit dependency.

sampling.hpp

@@ -2,13 +2,16 @@
 #ifndef SAMPLING_HPP
 #define SAMPLING_HPP
 
+#include <glm/vec2.hpp>
 #include <glm/vec3.hpp>
 
+using glm::vec2;
 using glm::vec3;
 
 extern const float PDF;
 
 extern float random01();
+extern vec2 sample_pixel(int i, int j, float w, float h, float a_ratio, float fov);
 extern void create_coords_system(const vec3 &n, vec3 &nt, vec3 &nb);
 extern vec3 sample_hemisphere(const float r1, float r2);
 extern void rotate_sample(vec3 & sample, vec3 & n);