It's sometimes difficult to manually unwrap simplified lightmap UVs for a mesh with many small geometric details. Enlighten mesh projection provides an alternative way to generate lightmap UVs using a target mesh. With this technique, the artist creates a simplified proxy mesh which approximates the original. Enlighten generates lightmap UVs by projecting the original mesh onto the proxy target mesh.

Target meshes are never drawn in the game runtime, so their associated mesh data isn't required at runtime.

Target meshes can be an effective way to generate simplified lightmap UVs for use with Enlighten. However, developing the skills to model good target meshes requires some practice.

You should only use this method when all of the following are true:

The mesh is large enough that it's not a good candidate for sharing a lightmap with other nearby meshes.
The mesh can't be lit efficiently using probes.
The Auto UV algorithm produces poor lightmap UVs for the mesh.
It's difficult to manually unwrap the UVs because the mesh is complex.

Good target meshes

A good target mesh is one for which mesh projection produces efficient simplified lightmap UVs for the projected meshes.

For complete control, we recommend to manually author a lightmap UV channel for the target mesh.

The proxy target mesh can be much simpler than the original detail mesh. Details that protrude from the mesh can be reduced to a simple smooth surface, as in the image below:

If the target mesh isn't authored correctly, the resulting distorted lightmap UVs may cause obvious lighting artifacts.

It's essential that the artist can quickly preview the result of lightmap UVs generated by Enlighten mesh projection. This feedback will help them improve the target mesh.

To ensure that the colour of light reflected by the proxy matches the original detail mesh, make sure that materials are applied to the proxy mesh in the same way as the original detail mesh.