Editing Lightmap (section)

==Limitations==

Lightmaps are composed of [[lumel]]s<ref>{{Cite web|url=http://www.flipcode.com/archives/Light_Mapping_Theory_and_Implementation.shtml|title=flipcode - Light Mapping - Theory and Implementation|last=Channa|first=Keshav|date=July 21, 2003|website=www.flipcode.com|archive-url=|archive-date=|accessdate=2015-09-07}}</ref> (lumination elements), analogous to texels in [[texture mapping]]. Smaller lumels yield a higher [[Image resolution|resolution]] lightmap, providing finer lighting detail at the price of reduced performance and increased memory usage. For example, a lightmap scale of 4 lumels per world unit would give a lower quality than a scale of 16 lumels per world unit. Thus, in using the technique, [[level design]]ers and [[3D artist|3d artists]] often have to make a compromise between performance and quality; if high resolution lightmaps are used too frequently then the application may consume excessive system resources, negatively affecting performance. Lightmap resolution and scaling may also be limited by the amount of disk storage space, bandwidth/download time, or texture memory available to the application. Some implementations attempt to pack multiple lightmaps together in a process known as ''atlasing''<ref>{{Cite web|url=http://http.download.nvidia.com/developer/NVTextureSuite/Atlas_Tools/Texture_Atlas_Whitepaper.pdf|title=Texture Atlasing Whitepaper|last=|first=|date=2004-07-07|website=nvidia.com|publisher=[[NVIDIA]]|archive-url=|archive-date=|accessdate=2015-09-07}}</ref> to help circumvent these limitations.

Lightmap resolution and scale are two different things. The resolution is the area, in pixels, available for storing one or more surface's lightmaps. The number of individual surfaces that can fit on a lightmap is determined by the scale. Lower scale values mean higher quality and more space taken on a lightmap. Higher scale values mean lower quality and less space taken. A surface can have a lightmap that has the same area, so a 1:1 ratio, or smaller, so the lightmap is stretched to fit.

Lightmaps in games are usually colored texture maps. They are usually flat, without information about the light's direction, whilst some [[game engine]]s use multiple lightmaps to provide approximate directional information to combine with normal-maps. Lightmaps may also store separate precalculated components of lighting information for semi-dynamic lighting with shaders, such as ambient-occlusion & sunlight shadowing.