Even with the introduction of lighting, our virtual objects don't look and feel real. This is because our lights are a simple approximation of the reflection behavior of the surface. There is a specific category of algorithms that help bridge the gap between the real-world lighting and the virtual-world lighting. These are called global illumination methods. Although these methods had been proven to be expensive to evaluate in real time, new methods have been proposed that fake the global illumination using clever techniques. One such technique is spherical harmonics lighting that uses HDR light probes to light a virtual scene having no light source. The idea is to extract the lighting information from the light probe and give a feeling that the virtual objects are in the same environment.

In addition, rendering of transparent geometry is also problematic since this requires sorting of geometry in the depth order. If the scene complexity increases, it becomes not only difficult...