I introduced post-processing materials in section 1.7 of this tutorial. However, description was very brief whereas post-processing should be treated as an important sub-system of the material system and therefore requires additional explanation. It will be provided in this section.
Post-processing materials in contrast to regular materials doesn't apply to single objects but to the scene as a whole after it has been rendered. That way all pixels of the rendered scene can be modified. There is no other way to this on current generation of GPUs than to do this in image space. That is scene has to be rendered (typically to a render target texture) and after that post-processing can be applied. Therefore real-time post-processing is similar to post-processing of movies and even post-processing photos! If you're familiar with applications like Photoshop or GIMP some of the effects might be already known to you. In post-processing you can perform water colour filtering, edge detection, image blurring amongst others.
nGENE Tech makes heavy use of post-processing effects. First of all by default it makes use of deferred shading which can be thought as an image-processing technique. Furthermore such effects like water and clouds are also done completely or partially in a post-process stage! What you basically have to understand is that post-processing gives you virtually unlimited opportunities and yet that it is often more efficient way of applying complex effects than doing them on the per object basis.
