ZBrushCentral

"Uv Check" Weirdness

ZBrush Usage Questions
#1

I have a problem model that crashes Zbrush whenever I try to compute a displacement map for it. These crashes are often caused by overlapping UVs, so I did a Uv Check and sure enough, Zbrush puts several red areas on the model. Problem is that none of these areas have overlapping UVs! I can look at the model in Maya and the red areas have good UVs. Some vertices are pretty close together, but they don’t overlap. If I apply AUVTiles to the model I can generate the displacement map without crash.

How good is the UV accuracy in Zbrush? Is it possibly considering close UVs to be overlapping even though they aren’t in other programs? How do I avoid these problems in the future? :slight_smile:

#2

There are many variables that can creep in when a model is being exported and imported between two applications. Many programs focus heavily on keeping the work inside themselves, and don’t do a very good job of importing/exporting data.

ZBrush is VERY precise with the UV’s. It has to be in order for AUVTiles to work correctly. It is also precise with how it imports and exports UV’s.

If your UV’s look “good, but close” in your other application, it’s very possible that the exporter introduced some overlap. Is it possible for you to move the mapping so that the edges aren’t so close together?

#3

Yes, n move UVs to get rid of the red areas. The low resolution of the generated Uv Check texture makes it sometimes difficult to find the areas, is there a way to increase the resolution of the generated texture?

Unfortunately the Displacement Map crash doesn’t seem to be related to overlapping UVs after all, there’s another, unrelated problem. I sent the mesh data to [email protected] for testing.

#4

By the way, too small of a map can cause UV boundaries which are not actually overlapping to fall into the same pixel when the displacement map is calculated. For example, if the mapping gives 1 pixel between points when the map is 2048 in size, they will fall on the same pixel at 1024.

#5

Well, I finally got the model to work by manually searching the UV layout and straightening out every concave UV quad that I could find. If the triangle edge in a concave quad connects the wrong vertices that can lead to an overlap (Zbrush even marks some of those), but I never had problems with it before because the 3D app usually takes care of keeping the quad “legal”. Somewhere along the line (Modo -> Maya -> Zbrush) this model must have gotten messed up beyond automatic repair…