ZBrushCentral

Multiple UV Groups, and offcenter importing

ZBrush Usage Questions
#1

I’ve been using ZBrush 3.1 for a few months, and suddenly I’ve found two problems I haven’t encountered before: I imported a character mesh, which in Maya had been one solid mesh, positioned at the origin. The immediate problem is that it comes into Zbrush slightly “off center” so that I need to reposition it to get proper X axis symmetry.

Second, after working on the mesh at a higher subdivision level for a while, I find that it’s not letting me use the ZMapper because it has multiple UV groups, and the instructions it gives me for addressing those groups one at a time don’t make sense to me. It says to go to Tools > Polygroups > UV Groups, and then to click Frame, but the UV Group button doesn’t do anything I can see (doesn’t open up a new box, doesn’t change color or flip a toggle, anything) and I can’t see any “Frame button” to click on. And now when I export the mesh back out, it’s been broken into two pieces.

Any ideas as to why any of this is happening?

#2

  1. Upgrade to 3.5R3. Normal map generation is improved. If you want top stick with Zmapper, after sculpting, split up a clone/copy of your model by UV group and create one map at a time. Overlapping UVs and Zmapper will likely ruin into problems.

  2. Recenter pivot by using the “s.pivot” button on the Transform Menu. If it’s still off center, try hiding all of the model except an equally weighted left-right portion of the model and use s.pivot. S.pivot seeks the geographic center of what is visible.

#3

I plan to get 3.5 soon, and I have found workarounds for the off-center thing (although your way sounds easier), it still seems to me that neither of these things should be happening in the first place. (Neither happened when I was using my school’s copy of ZBrush. I’m currently using the 3.1 demo, and plan to buy 3.5 later this month.)

#4

3.5 does a better job of loading .objs on-center and scaled properly. There are vagaries and rounding errors in the .obj format going from application systems to application system and ZB is somewhat sensitive to these variations due to its optimized representation of objects in 3-space (which is what enables it to work with meshes ten times denser than your average 3D app.)

You may want to get your hands on the poser scaler plugin for ZB 3.1 as it can help with some .obj handling. Its functionality is now built into the ZB 3.5 importer/exporter.

-K

#5

Thanks, however an additional note: the breaking the object into UV groups for no reason phenomenon is not limited to OBJs. I played around a bit with the basic Zbrush starting meshes (dog, biped, soldier, etc). With one or two subdivisions I could Zmap them just fine, but after subdividing 3-5 times (it varied from mesh to mesh) I got the same “Object is in multiple UV groups, can’t Zmap” message.

I’m also still particularly confused about the instructions Zmapper gives me about how to map to different UV groups, even if I wanted to try (in case it wasn’t clear, I DON’T want separate UV groups for anything). Again:

Tools > Polygroups > UV Groups, and then to click Frame, but the UV Group button doesn’t do anything I can see (doesn’t open up a new box, doesn’t change color or flip a toggle, anything) and I can’t see any “Frame button” to click on.

What is the UV Groups buttons supposed to do? I assume it’s supposed to open up into a menu with a Frame button, unless there’s a frame button somewhere else on the screen that I’m missing.