Implementing GPU-based ray tracing

To this point, all of the recipes rendered 3D geometry using rasterization. In this recipe, we will implement another method for rendering geometry, which is called ray tracing. Simply put, ray tracing uses a probing ray from the camera position into the graphical scene. The intersections of this ray are obtained for each geometry. The good thing with this method is that only the visible objects are rendered.

The ray tracing algorithm can be given in pseudocode as follows:

For each pixel on screen
  Get the eye ray origin and direction using camera position
  For the amount of traces required
    Cast the ray into scene
    For each object in the scene
      Check eye ray for intersection 
      If intersection found
        Determine the hit point and surface normal 
        For each light source 
          Calculate diffuse and specular comp. at hit point
          Cast shadow ray from hit point to light 
        End For
        Darken diffuse component...