Baked GI Lighting

When 'baking’ a ‘lightmap', the effects of light on static objects in the scene are calculated and the results are written to textures which are overlaid on top of scene geometry to create the effect of lighting.

Left: A simple lightmapped scene. Right: The lightmap texture generated by Unity. Note how both shadow and light information is captured.

These ‘lightmaps’ can include both the direct light which strikes a surface and also the ‘indirect’ light that bounces from other objects or surfaces within the scene. This lighting texture can be used together with surface information like color (albedo) and relief (normals) by the ‘Shader’ associated with an object’s material.

With baked lighting, these light textures (lightmaps) cannot change during gameplay and so are referred to as ‘static’. Realtime lights can be overlaid and used additively on top of a lightmapped scene but cannot interactively change the lightmaps themselves.

With this approach, we trade the ability to move our lights at gameplay for a potential increase in performance, suiting less powerful hardware such as mobile platforms.