A texture used in 3D rendering which is used to simulate lighting effects on a surface instead of having to raytrace the scene. Lightmaps are usually in greyscale, but can be coloured for coloured lights.

a second texture which is precalculated by a raytracer, in order to give a surface realistic-looking lighting

A lightmap is a 3 D engine light data structure which contains the brightness of surfaces in a video game. Lightmaps are precomputed and used for static objects. Quake was the first computer game to use lightmaps to speed rendering while preventing floors from looking distorted.