Lightmaps are a type of surface caching in which the brightness at various points of the surface are pre-calculated and stored in a texture map (much the same way that a texture map, normal map, or displacement map is). They are less computationally expensive than calculating lighting on the fly.
To create a lightmap from an existing UV map
- Duplicate the existing map.
- (Optional) Set a uniform Texel density for the entire mesh (unless there are areas that you specifically want to have a higher or lower resolution). For more information, see the
Texel Density tool.
- Use the
Unstack Shells command to ensure that no shells overlap.
If you still end up with overlapping UVs, perform edge cuts to make them smaller and then unstack again (ensuring proper shell spacing).
The layout is now ready for lightmapping.