Using UV maps only for bitmap-textured parts of a mesh


Can I cheat at UV unwrapping the entire model by only unwrapping parts that have textures on them, while I scale the solids’ unwraps to a single point? And then use this on sketchfab or other sites?

I have a mesh made up of a lot of pieces that I want to upload to sketchfab. Not for printing.
It now needs to be textured, but unwrapping will get quite complex and more importantly, I probably need to bake the procedural textures to an image before I upload it. However, large parts of the mesh do not have textures, but are basically made from a solid colour PBR.

The way I recall Sketchfab uses a mesh’s material slots to assign materials and textures. I have made the materials in Blender satisfactorly realistic, and am wondering whether skipping unwrapping the solid parts of the mesh makes sense. Furthermore,large parts of the model are hidden from view (manifold meshes interlocking and covering each other up), so lot of UV space would go to waste. I don’t want to make a group of16 bit 8k textures - it would be an enormous file not to mention the time all the unwrapping would take. What can I do instead? Any shortcuts?


Yes, it makes sense if you need it.
But an UVmap adds UVcoordinates to all vertices of your mesh, so either you use them or not, they will still be unwrapped. If some faces have a none textured material assigned to them, it won’t matter what coordinates they have. Scaling all the parts that don’t need UV coordinates into a little point might be usefull if you can have only one material in the object.

If you move unused UVs (collapsed or not) outside the UV range, you can setup mask as well, preventing the outside stuff to get a color assigned.

I just remembered that game engines use lightmaps. Is it correct to think that scaling some UVs down will cause bad shading?

Lighmaps are textures, so your ‘bitmap-textured parts of a mesh’ will be the whole mesh.

Some engines allow multiple UVmaps, and you can have a global UVmap for things like AO/lighmaps (which don’t require too much texture detail), and specific UVmaps for textures with high and localized texture details.