A lightmap is a 3D 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. Before lightmaps were invented, 3D engines used Gouraud shading for the floors and walls which caused shimmering. The most common methods of lightmapping are to either precompute vertex lighting by using distance from each vertex to a light, or by using multitexturing to apply a second texture which contains the lumel data.

Lightmaps are scaled using luxels. The smaller the luxels, the higher the resolution (and quality). However, this often comes at the price of performance. For example, a lightmap scale of 32 luxels per world unit would give a lower quality than a scale of 16 luxels per world unit, although it may improve in-game performance. It's important for map makers to make a compromise between performance and quality. If a low luxel per world unit scale is set too frequently then the game is likely to lag when played.