The goal of this project is to add Cell Shading capabilities to the Quake III engine with Real-time performance. In order to provide such a feature the production team 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 they decided to apply a simple blur filter to reduce hard-edges on textures and increase the flatness effect. To produce the cell shading effect there is no use of graphics card shaders, so the implementation can run with almost any gfx card. The edge 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 this modified engine just place the 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.