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Issues when mirroring after baking half-mesh

guitarguy00
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guitarguy00 polycounter lvl 7
Hey there,

I have recently been trying to go extreme with optimizing UV space and have seen videos on people deleting a mesh down the middle, UV-unwrapping it, baking it and then mirroring the mesh later. Basically saving on UV space as the other half would be offset outside the 0-1 space. However when I attempt this I get weird shading on areas even where there are no UV seams? Am I missing something? A baking setting in Toolbag? A setting in Blender prior to exporting out(I have tried triangulation)? I smooth UV islands as per normal.  In this example the UV seams are at the bottom of the cylinder, yet I still get weird seams at the top? Any help would be much appreciated. 

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  • stray
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    stray triangle
    At a guess, I would suspect that the key to this method is preserving the normals of the "half-mesh", as if they were part of the whole mesh. If you just delete the half the normals on the edges are bound to change, no?
  • guitarguy00
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    guitarguy00 polycounter lvl 7
    stray said:
    At a guess, I would suspect that the key to this method is preserving the normals of the "half-mesh", as if they were part of the whole mesh. If you just delete the half the normals on the edges are bound to change, no?
    Ahhh yes quite right. Now the question is, how is it done with no issues like I see in some videos..
  • stray
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    stray triangle
    Well, you could transfer custom normals from whole mesh...

    That said, is there any reason for baking before restoring the other half? Can't you simply bake symmetrical mesh..?
  • guitarguy00
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    guitarguy00 polycounter lvl 7
    stray said:
    Well, you could transfer custom normals from whole mesh...

    That said, is there any reason for baking before restoring the other half? Can't you simply bake symmetrical mesh..?
    Definitely will try baking with the mirrored parts offset. Just thought it would be quicker this way cause I am using Blender(previously a 3DS guy) so thought it would be easier. Turns out I was wrong haha.
  • Eric Chadwick
    The trick is to delete half the mesh, UV, mirror the mesh, weld the vertices along the mirror seam, offset the UVs for the mirrored parts 1 unit in UV space, then bake.
    http://wiki.polycount.com/wiki/Normal_Map_Modeling#Mirroring
  • gnoop
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    gnoop sublime tool
    In Blender it's enough to just check in the  merge checkbox in the  mirror modifier  and shift U or V  in   modifier "data"  drop down.   I mean if  you are ok with same texture on other half.       Pretty quick IMO .

    if you need to give the  mirrored half  some select-able attribute   just create  yourthing_R  and yourthing_L  vertex groups and apply one to original half accordingly . It will stay in that half only.    Also mirror modifier respects  edited /custom vertex normals vs  when you merge manually .
    Also it would be wise to keep initial cylindrical objects as a source to transfer vertex normals from using data transfer modifier if you decide later to make the  halves unique  .
  • guitarguy00
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    guitarguy00 polycounter lvl 7
    The trick is to delete half the mesh, UV, mirror the mesh, weld the vertices along the mirror seam, offset the UVs for the mirrored parts 1 unit in UV space, then bake.
    http://wiki.polycount.com/wiki/Normal_Map_Modeling#Mirroring
    Thanks heaps, makes sense. I will just to it this way.
  • guitarguy00
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    guitarguy00 polycounter lvl 7
    gnoop said:
    In Blender it's enough to just check in the  merge checkbox in the  mirror modifier  and shift U or V  in   modifier "data"  drop down.   I mean if  you are ok with same texture on other half.       Pretty quick IMO .

    if you need to give the  mirrored half  some select-able attribute   just create  yourthing_R  and yourthing_L  vertex groups and apply one to original half accordingly . It will stay in that half only.    Also mirror modifier respects  edited /custom vertex normals vs  when you merge manually .
    Also it would be wise to keep initial cylindrical objects as a source to transfer vertex normals from using data transfer modifier if you decide later to make the  halves unique  .
    Thanks, I will do it the way you mentioned.
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