Is there a way to unwrap a symmetrical model so that the UVs for each side overlap? I'm working on a model which will have the same patterns on each side, and I'd like to avoid having to create half of a texture which isn't used, and make sure both sides match exactly
So, what you need to do is mark seam where the cut is supposed to happen, then unwrap the whole mesh with U > Unwrap, then in the UV/Image Editor, mirror the half with a SX-1, then move it, rotate it so that it overalys its mirrored version. In the UV/Image Editor you can use the Snap (vertex mode) option if you want the vertices to snap perfectly.
After wasting a good amount of time on this exact issue, I've found a good solution; one that does not effect multi-res, vertex groups, shape keys, or anything else of the sort, as it works entirely in texture-space.
- In edit mode, select the faces you wish to mirror on the side of the mesh with the correct UVs
- Now select these faces in the UV editor
- In the UV editor, under the UV menu, select "Copy UVs"
- Return to edit mode and mirror your selection with Ctrl + Shift + M
- With the corresponding faces selected in the UV editor, select "Paste UVs" from the UV menu
This method will stack topologically identical sections on top of each other, for example: a bottom lip would get stacked on top of a top lip. To avoid this, repeat the process for each section individually.