Implementing GPU-based path tracing

In this recipe, we will implement another method, called path tracing, for rendering geometry. Similar to ray tracing, path tracing casts rays but these rays are shot randomly from the light position(s). Since it is usually difficult to approximate real lighting, we can approximate it using Monte Carlo-based integration schemes. These methods use random sampling and if there are enough samples, the integration result converges to the true solution.

We can give the path tracing pseudocode as follows:

For each pixel on screen
  Create a light ray from light position in a random direction 
  For the amount of traces required           
    For each object in the scene
      Check light ray for intersection 
      If intersection found
        Determine the hit point and surface normal 
        Calculate diffuse and specular comp. at hit point
        Cast shadow ray in random direction from hit point  
        Darken diffuse component based on shadow result...