ZBrushCentral

ZBrush changes mesh transposition on merging and re-topologizing

ZBrush Usage Questions
#1

I am new to ZBrush, so hopefully, there is a simple oversight here.

The problem I have is that ZBrush is consistently shifting both position and orientation on export. If I import the mesh and immediately export, this problem is not seen. However, if I make adjustments, merge down with other subtools, or re-topologize (with ZRMesher), it will always come out pointing downwards and shifted off the world center on exports.

I have looked at the default Import/Export settings in Preferences, and it appears there is an X and Y flip on both import and export, so this should not the be issue. The change in tansposition happens without any change to position or orientation.

I suspect the problem is from merging down, but this is a huge problem when constructing huge meshes, especially if you are inserting other meshes onto a master mesh. The merge down, in that case, would essentially push the master mesh to whatever position the lower subtool is located at.

So my question is — is there any way to force ZBrush to honor coordinates (position and orientation) for the first subtool or, alternately, store its position and orientation and then restore it once the merges have happened?

#2

I was able to find a workaround for this problem, but it’s still not clear why it is happening. Here are the steps for anyone else running into the issue:

  1. Export OBJ with default settings (eFlipY, eFlipZ).
  2. Import OBJ into Blender with default -Z forward, Y up.
  3. Export OBJ from Blender set to -X forward, Z up.

It will then import back into the original program. It appears that ZBrush, at some point, flips X and Z axes, and there is nothing in app settings to sidestep this behavior.

Hopefully, someone will have an idea why ZBrush does this in the first place.