Unwrap and unweld the same edges


I really spent too much time unwrapping one simple bookcase. It gave me all kinds of problems in external programs. My goal is to prepare an asset with two UV channels, one for the texture and second for good quality (optimized) custom lightmaps for the Unreal Engine. Because we can’t export multiple UVs from Rhino, part of the job I’m doing in Blender.

uv mapping problems.3dm (2.0 MB)

That was the story, now to the problems:

  1. Recently, something was fixed about broken UVs but this polysurface still makes bad UVs inside Blender (in Rhino it looks fine). I consciously made a decision to use Fillet Edge instead of light & quick Edge Softening, because with the second method I was unable to export good UVs out of Rhino.
    Unfortunately, I couldn’t avoid broken UVs anyway.

  1. Second object is unwrapped with some errors (smaller and harder to notice, but still).
    Although, I am bringing it because of other reasons. All the mesh parts of that object are not welded together. Basically, every surface makes a mesh that is not welded to another.

What I need is a mesh with unwelded edges only where edges were selected to be cut for unwrapping.

Edges selected for the Unwrapping

Unwelded edges of the extracted render mesh

Why this is important for me? Because I will have multiple objects like that and I want to pack them together on one lightmap texture by automatic packing method (UVPackmaster 2). If each object is not welded into one, their parts will be taken and scattered around UV space. This will make gaps between each mesh part and cause problems with the Lightmap discontinuities.
(I can maybe group them together inside UVP 2 but that’s a lot of additional and manual work)

  1. Would it be possible to Weld hard mesh edge (so the texture islands are connected) but not modify normals, so the hard edge looks correct?

Surprisingly, Rhino Obj export has some advantages over fbx and this helps to overcome point 2 & 3. If this could work for fbx export that would be very nice. :slight_smile:

Hi @Czaja

This will be fixed in Rhino 7 SR4.

I’ve logged this as RH-62670 FBX export: option to connect topological vertices

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