my ID map is just a blank gray

WindchILL

I'm doing the bake by same name in Substance Painter 2 using a UDIM workflow. Every other texture map bakes fine except for the ID color map. I exported the highpoly from zbrush as FBX and all the subtools had their own polypaint color so I'm not sure why it is coming out as solid gray. In SP2 I tried specifying color source as vertex color the first time and material color the second time, but both dont work (vertex color just gave me an error and material color gave me the gray output).

Bek

If vertex colour bake gave you an error it was probably telling you that the mesh has no vertex colours. What did the log say? If so verify they're being exported correctly from zbrush (open it in another program and see if the vcols exist) and if they do, then it's substance not reading that info. Otherwise you're not exporting them correctly. If it doesn't mess up using match-by-name, you could try .obj from zbrush.

Martin_H

I have just had a similar problem. It turned out to be caused by one of my exported highpoly meshes (that wasn't even aligned with the lowpoly for the bake) not having vertex colors (using blender and no vertex color layer generated for the mesh). It was fixed for me by adding a vertex color layer for the offending mesh and re-exporting.

I don't know if this is a limitation of the FBX format, or a bug, but I feel like people should know about this quirk.