It is common to want to bring your model out of zbrush to do up the uv’s (although it is always a better idea to deal with them BEFORE getting into zbrush), but importing the edited .obj back into zbrush can be a hassle, esp when your model ‘explodes’ inexplicably when you move up the subdiv level.
Example of a exploded model:
Exploded model
To save a few souls, below is what worked for me and you can try to take note of the following when nothing seems to work:
(Tested with ZBrush 3.1 and Maya 2008)
In ZBrush
When exporting from zbrush, make sure you are at the lowest subdiv level.
Under Tool->Texture, make sure you have UV enabled:
Enable UV
Under Tool->Export, turn off the ‘Grp’ option and on the ‘Mrg’ option as such:
Export from ZBrush
In Maya
Go to File->Import Options, and set the settings as below:
(Note: When editing DO NOT move the vertices in maya, only edit the UV’s)
When exporting, go to File->Export Selection Options. Select OBJ and off all the File Type Specific Options in the last section:
Back in ZBrush
Import the .obj while still at subdiv level 1.
After import, move up a level to check if it explodes.
Feel free to leave any comments whether this worked for you and also for others to benefit from your experience =)