Non-Photorealistic Postprocessing Filters in MotoGP 2
Author(s): Shawn Hargreaves.
In Book: Wolfgang Engel, Image Space, Wordware Publisher, Vol. ShaderX2 - Shader Tips and Tricks, September,
2003.
[BibTeX] 
Abstract:
Stylised rendering techniques are cool, and with programmable shader hardware they can be easy to implement, too. This article discusses how such effects
can be applied as a postprocess over the top of a conventional renderer. The goal is to have minimal impact on the structure of an existing engine, so that if
you are already using a hundred different shaders, adding a new stylised filter should only increase this to a hundred and one, rather than needing a
modified version of every existing shader.
The idea is to render your scene as normal, but to an offscreen texture instead of directly to the D3D backbuffer. The resulting image is then copied across
to the backbuffer by drawing a single fullscreen quad, using a pixel shader to modify the data en-route. Because this filter is applied entirely as a 2D image
space process, it requires no knowledge of the preceding renderer. In fact, these techniques can just as easily be used over the top of video playback as with
the output of a realtime 3D engine.