Started scene reader. Added libjson-spirit dependency.

sampling.cpp

@@ -9,6 +9,7 @@ using glm::mat3;
 using glm::abs;
 using glm::normalize;
 using glm::cross;
+using glm::radians;
 using glm::pi;
 
 const float PDF = (1.0f / (2.0f * pi<float>()));
@@ -17,6 +18,20 @@ float random01() {
   return static_cast<float>(rand()) / static_cast<float>(RAND_MAX);
 }
 
+vec2 sample_pixel(int i, int j, float w, float h, float a_ratio, float fov) {
+  float pxNDC;
+  float pyNDC;
+  float pxS;
+  float pyS;
+  pyNDC = (static_cast<float>(i) + random01()) / h;
+  pyS = (1.0f - (2.0f * pyNDC)) * glm::tan(radians(fov / 2.0f));
+  pxNDC = (static_cast<float>(j) + random01()) / w;
+  pxS = (2.0f * pxNDC) - 1.0f;
+  pxS *= a_ratio * glm::tan(radians(fov / 2.0f));
+
+  return vec2(pxS, pyS);
+}
+
 /* Sampling functions pretty much taken from scratchapixel.com */
 void create_coords_system(const vec3 &n, vec3 &nt, vec3 &nb) {
   if (abs(n.x) > abs(n.y))