Quake III Arena Cell Shading's goal is to add Cell Shading capabilities to the Quake III engine with Real-time performance.
In order to provide such feature we have decided to use Kuwahara filter. Kuwahara filter is a noise-reduction filter that preserves edges.
It uses four subquadrants to calculate the mean and variance and chooses the mean value for the region with the smallest variance.
To increase the hand-painted effect we have decided to apply a simple blur filter to reduce hard-edges on textures and increase the flatness effect.
To produce the cell shading edege effect we use no gfx card shaders, so our implementation could run with almost any gfx card. This effect is produced by painting backface polygons with a thick wireframe without textures and repaint all the scene, but this time, with textures.
To test our modified engine just place our binary in your game's folder to frag all day long!
Ensure you have a copy of Quake 3 Arena installed on your PC. You're going to need the artwork/content from the game because it is not redistributable.