$lightwarptexture

The technique was first used in

Day of Defeat: Source's snow maps, such as Kalt.

$lightwarptexture is a cornerstone of

Team Fortress 2's illustrative character rendering.

Posterized color can be achieved, but lighting must be tightly controlled.

Template:Shaderparam It tints texels depending on their brightness. It can be thought of as localized color correction.

Important:$lightwarptexture must be specified after all other textures, otherwise it will overwrite them.

Note:Requires phong on VertexLitGeneric in

Counter-Strike: Source.

Todo: Do games other than

require phong for this to work?

Lightwarp textures

A lightwarp texture is a one-dimensional strip of pixels. Dark texels will be tinted with the colour on the left-hand side, and bright texels with the colour on the right. 50% gray means no tint.

Examples

snow_warp: $dod\materials\ground\snow_warp$; This is the lightwarp texture used in the Day of Defeat: Source screen to the right. It is designed to add a subtle bluish tint to darker snow without affecting brighter regions.
pyro_lightwarp: $tf\materials\models\player\pyro\pyro_lightwarp$; This is applied to all Team Fortress 2 characters, not just the Pyro. It creates the high-contrast shadows with red-tinged terminators typical of the illustrative art the game apes.
Posterized: This custom warp texture creates a posterized "line art" style. Enabling lightwarp alone isn't enough however: ambient lighting must be at 0 to make unlit areas black, and world lighting must become viewer-dependent to ensure that shadows are always cast.
Cel Shading: Cel shading can make objects look more cartoony by replacing the smooth lighting gradient with sharp steps.