Added camera abstraction.

sampling.cpp

@@ -0,0 +1,45 @@
+#include <cstdlib>
+
+#include <glm/glm.hpp>
+#include <glm/gtc/constants.hpp>
+
+#include "sampling.hpp"
+
+using glm::mat3;
+using glm::abs;
+using glm::normalize;
+using glm::cross;
+using glm::pi;
+
+const float PDF = (1.0f / (2.0f * pi<float>()));
+
+float random01() {
+  return static_cast<float>(rand()) / static_cast<float>(RAND_MAX);
+}
+
+/* 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))
+    nt = normalize(vec3(n.z, 0.0f, -n.x));
+  else
+    nt = normalize(vec3(0.0f, -n.z, n.y));
+  nb = normalize(cross(n, nt));
+}
+
+vec3 sample_hemisphere(const float r1, float r2) {
+  float sin_t = glm::sqrt(1.0f - (r1 * r1));
+  float phi = 2 * pi<float>() * r2;
+  float x = sin_t * glm::cos(phi);
+  float z = sin_t * glm::sin(phi);
+  return vec3(x, r1, z);
+}
+
+void rotate_sample(vec3 & sample, vec3 & n) {
+  vec3 nt, nb;
+  mat3 rot_m;
+
+  create_coords_system(n, nt, nb);
+  sample = vec3(sample.x * nb.x + sample.y * n.x + sample.z * nt.x,
+		sample.x * nb.y + sample.y * n.y + sample.z * nt.y,
+		sample.x * nb.z + sample.y * n.z + sample.z * nt.z);
+}