A UV layout is the flat pattern a 3D surface is cut into so a 2D image can be wrapped onto it. Generated meshes usually arrive with a layout that technically exists and is not much use.
Why generated UVs are poor
Reconstruction produces UVs as a by-product of building the mesh, not as a considered layout. The result is typically fragmented into many small islands, unevenly scaled, and seamed wherever the algorithm found it convenient rather than where a seam would be hidden.
That is survivable if you never touch the texture again. It becomes a problem the moment you want to paint, bake, or tile a material.
What a good layout looks like
- Even texel density. Every part of the surface gets a similar share of the texture. Otherwise one area is crisp and another is blurry at the same texture resolution.
- Few, large islands. Fewer seams, less wasted space, easier painting.
- Seams in hidden places. Under an arm, along a hard edge, behind a join — not across a face.
- No overlaps, unless deliberate. Overlapping islands share texture space, which is a memory optimisation and a painting hazard.
Order of operations
Unwrap after retopology, never before. Retopology creates a new mesh, and a new mesh has no relationship to the old layout — unwrapping first means doing it twice.
The usual sequence is: generate, retopologise, unwrap, then texture or bake.
Face count limits
Unwrapping algorithms have practical limits and dense meshes exceed them quickly. If a model is too heavy to unwrap, that is a signal it needs retopology first rather than a bigger machine.