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UV tiles or UV Regions, and GrpSplit crashes.

ZBrush Usage Questions
#1

Hello everybody.

I’m currently trying to work out the best way of dealing with UV tiles, also called UV regions, in zBrush. I have read through the FAQs and got a lot of good information, but I’m still having a lot of issues getting this to work.

First, to clear up what I mean by UV Tiles, or Regions. Normally UVs are in a 0,1 space. But as I have an object that is quite long and will need a lot of detail, I want to stretch the UVs over several tiles. Think of a Cylinder with a single cap. I put the UVs for the cap (planar) in 0,1. Then I stretch the UVs for the body (cylindrical) of the cylinder over 1,1 and 2,1. Reading left to right, essentially.

Now the process I have been trying, recommended by the FAQs, is:


  • setup the tiled UVs in another application (Maya in my case) and import that object into zBrush.
  • Subdivide and paint up colour and displacement as normal.
  • When you are ready to export, choose Tools>Polygroups>UV group. This will split up the tiles into groups.
  • Then choose Tools>SubTools>GrpSplit. This should put each of the polygroups into their own subTool layer thing.
  • Export normal and colour maps for each subtool.
Okay, so my problem is this. Every time I choose GrpSplit I get zBrush crash. Almost every time. The only way I can do it without getting a crash, is to drop the subdivsion levels down to 1, and delete all higher. Which means I lose all that information.

I have tried this with simple primitives, and I thought it had something to do with the way the UVs were laid out, but now I think it’s a polyGroup issue. If I bring a mesh in with no UV tiles, and just do a manual select over the cap of the cylinder, and make that my group, I still get a crash when using GrpSplit.

Are there any rules or guide lines for how you are meant to or not meant to split up polyGroups? I found a cylinder with no caps, but stretching over 4 tiles worked perfectly fine.

Any help would be greatly appreciated as I have been battling with this for two days now. And I really need to understand how to get this working well.
I have seen several posts on here by people saying they have had similar problems, but then the resolve it themselves and either don’t say, or know, how they fixed it.

Thanks
Campbell.