Lightmap uv's are stacked after running Mesh.CombineMeshes

I am using Mesh.CombineMeshes to merge several static pieces of building geometry into a single mesh. When I do this, and then generate lightmaps, all of the instances of a particular piece that were merged together have the same indexes into the lightmap.

This image shows the 2 objects lightmapped, everything works great

This image shows the 2 objects after being run through Mesh.CombineMeshes, the top box is using the lightmap data that is correct for the bottom box

I’m not sure why the lightmap system is thinking that both parts of the mesh should be using the same uv’s or to get it to generate some unique texture space for all parts of the mesh.

Ever thought of the directional light that is directing the light the same way?