$lightwarptexture (DX9+) is a material shader parameter available in all Source games since Source 2006. It tints texels depending on their brightness. It can be thought of as localised color correction.
$lightwarptexturemust be specified after all other textures, otherwise it will overwrite them.
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.
- This is the lightwarp texture used in the DOD Source screen to the right. It is designed to add a subtle bluish tint to darker snow, without affecting brighter regions.
- This is applied to all TF2 characters, not just the Pyro. It creates the high-contrast shadows with red-tinged terminators typical of the illustrative art the game apes.
- This custom warp texture creates a posterised "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 can make objects look more cartoony, by replacing the smooth lighting gradient with sharp steps.
Other possible uses of
$lightwarptexture include contrast enhancement, tweaking vertex lighting shadow transitions, highlight softening and more.