Editing Lightmap (section)

==Creation==
When creating lightmaps, any lighting model may be used, because the lighting is entirely precomputed and real-time performance is not always a necessity. A variety of techniques including [[ambient occlusion]], direct lighting with sampled shadow edges, and full [[Radiosity (computer graphics)|radiosity]]<ref>Jason Mitchell, Gary McTaggart, Chris Green, [https://steamcdn-a.akamaihd.net/apps/valve/2006/SIGGRAPH06_Course_ShadingInValvesSourceEngine.pdf Shading in Valve's Source Engine]. ([[PDF]]) Retrieved Jun. 07, 2019.</ref> bounce light solutions are typically used. Modern 3D packages include specific plugins for applying light-map UV-coordinates, atlas-ing multiple surfaces into single texture sheets, and rendering the maps themselves. Alternatively game engine pipelines may include custom lightmap creation tools. An additional consideration is the use of compressed [[S3 Texture Compression|DXT]] textures which are subject to blocking artifacts – individual surfaces must not collide on 4x4 texel chunks for best results.

In all cases, [[soft shadows]] for static geometry are possible if simple occlusion tests (such as basic [[Ray tracing (graphics)|ray-tracing]]) are used to determine which lumels are visible to the light. However, the actual softness of the shadows is determined by how the engine interpolates the lumel data across a surface, and can result in a [[Pixelation|pixelated]] look if the lumels are too large. See [[texture filtering]].

Lightmaps can also be calculated in real-time<ref>November 16, 2003. [http://joshbeam.com/articles/dynamic_lightmaps_in_opengl/ Dynamic Lightmaps in OpenGL]. Joshbeam.com Retrieved Jul. 07, 2014.</ref> for good quality colored lighting effects that are not prone to the defects of Gouraud shading, although shadow creation must still be done using another method such as [[stencil shadow volumes]] or [[shadow mapping]], as real-time ray-tracing is still too slow to perform on modern hardware in most 3D engines.

[[Photon mapping]] can be used to calculate global illumination for light maps.