My question is related to all the meshes that have been created with the modifier mirror.

Let's take an easy example:

enter image description here

This mesh can be divided in 2 parts, PART A & PART B: equal shape.

In order to optimize the space for my Normal map

1) i delete the PART A of my low poly / high poly

2) In this way, having only PART B, i unwrap PART B and bake it with the high poly

the results is this one; not so good but it's not the point of my question

enter image description here

3) i mirror my mesh in order to create again my PART A and i have now this one

enter image description here

4) as you can see the Uv map of PART A overlap, in the same position for each island, the uvmap of PART B and then they share the same portion on normal map

enter image description here enter image description here

When i watch the final render however i saw this result

enter image description here

There is a line that cut my mesh in the half. Is it possibile to fix this problem? Does this prove that it's impossible to overlap two identical uv maps?

  • $\begingroup$ Did you have "Clipping" checked when you added the Mirror Modifier? $\endgroup$
    – Dontwalk
    Jun 7 '16 at 21:27
  • $\begingroup$ the mirror modifier can mirror UV coordinates $\endgroup$
    – user2816
    Jun 7 '16 at 21:28
  • $\begingroup$ Yes i have "clipping"; @root : my focus isn't mirror the uv map; is to save as much space as possible for my uv map. In order to reach it i want to use only half mesh, i.e. half uv map, and then mirror the other part (that will overlap the first) $\endgroup$
    – Fuboski
    Jun 7 '16 at 21:31
  • $\begingroup$ just to be sure , you have two identical uv maps or uv islands? there is remove double uv maps that can make them overlap perfectly. $\endgroup$
    – user2816
    Jun 7 '16 at 21:59
  • $\begingroup$ I have identical uv islands overlapped. The uv map is unique $\endgroup$
    – Fuboski
    Jun 7 '16 at 22:44
  1. Have half of your mesh with UVs done.* enter image description here
  2. Bake your stuff.
  3. Mirror your model. enter image description here

Your UVs will be overlapping but not at the time of baking. If you bake while overlapping Blender will get confused and want to put two images (even though they're exactly the same, Blender doesn't know that) at the same place and that's why it comes out weird.

*If you already have your UVs overlapping, applied the Mirror modifier and rather not delete half of the mesh to mirror it again, then you can select one of the halves' UVs, scale them super small and put them in a corner, like this: enter image description here Bake your stuff and then ctrl + Z so that the UVs are overlapping again, but your stuff is already baked.

Short answer: Overlapping only causes problems while the baking process happens. Bake only half of your model and then overlap the UVs.

  • $\begingroup$ Sorry i can't understand . . . can you explain better the method? $\endgroup$
    – Fuboski
    Jun 8 '16 at 10:42
  • $\begingroup$ Sorry, is that a bit better? I'll add screenshots in a couple of hours. $\endgroup$ Jun 8 '16 at 18:03
  • $\begingroup$ Sorry i'm trying to follow the passages but doesn'twork $\endgroup$
    – Fuboski
    Jun 8 '16 at 18:33
  • $\begingroup$ Sorry (I had to start with sorry again to keep it going haha), I don't have access to Blender right now so can't send you the screenshots, I'll post them as soon as I can. $\endgroup$ Jun 8 '16 at 18:40
  • $\begingroup$ Edited. And no problem, hope I understood your question correctly $\endgroup$ Jun 8 '16 at 21:19

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