Ive never actually tried exporting meshes originally built in zbrush. max's obj export works fine going into and then back out of zbrush which is my normal workflow. I think you need to change the settings of the object inside zbrush before you export. something like "make polymesh 3d" .

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Hello Tyson
EDIT: Come to think of it, I'm thinking maybe these errors are sort of like watermarks in that Pixologic doesn't want people using their geometry outside of the applications. I have no problem bringing "my own" meshes back and forth between applications. Actually, I can even bring their default primitive models/tools over to max, and they do open, it's just they don't pass the STL check, which again, I think is a kind of watermark.
But to follow up on what you mentioned in regards to exporting the mesh, the meshes I'm exporting have already been chanced to make polymesh 3d, but either way I tried both ways. I read a few posts where some other people noticed the problem after they upgraded to zBrush3.1, so I'll just wait and see what comes up.

By the way, this if off topic but, there was an issue with zBrush3.1 with the undo buttons not working for some people, including myself, and the staff mentioned a quick fix, which worked good.
In the ZBrush3\ZStartup\Hotkeys folder there will be a file named StartupHotkeys.txt, if you should have this issue, you can edit it and add these lines to the file and restart ZBrush:

[EDIT:UNDO,634]
[EDIT:TOOL:UNDO,634]

[EDIT:REDO,890]
[EDIT:TOOL:REDO,890]


Adding those lines worked for that undo issue.

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So Ive just tried exporting a sphere primitive from zbrush and I get errors, specifically 220 coincident vertices. doing a weld operation with a .01 threshold fixed the problem and it passes the stl check modifier too. I also tried exporting a zsphere mesh which worked without the errors. I don't think this is a "watermark" to stop people from exporting geometry. if they didnt want people exporting it just wouldnt be possible right. plus the program is pretty much designed to be used in this way jumping between apps for rendering.
I suggest that using primitives from your 3d app is the way to go and seeing as zspheres seem to work theres not really much reason to create geometry in zbrush from scratch. zspheres are awesome but theres not really much benefit to using the zbrush primitives.
Is there are reason why you need to use them?

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Hello Tyson. That's cool you got it to work by welding. Just curious, I know how to weld two vertexes, but how would you select a large number of bad vertexes on a more complex object to be welded? Like the zBrush head for example, there are probably well over 200 bad vertexes which need to be welded, but how do you selected just the bad ones?

By the way, I'm not using the zbrush geometry for anything other than to just have something to experiment with. I just wanted something quick that I could play around with shaping, then later see what it looked like when imported into Max. I'll be using my own geometry coming from max when I actually do make things.

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yeah its certainly better to use a nice clean mesh exported from max for anything other than practice.
I would recommend building a quick face mesh in max that is very simple with each polygon roughly the same size that also has all the extra extrusions like nose and chin etc. for doing quick zbrush studies. one very simple head mesh could become a million different characters and if the base mesh is clean and low res you can easily use it for final work by exporting a slightly higher subdivision mesh and displacement/normal maps. If you start with a sphere the details have to be stretched out of the shape which wont works as well ans some strategically placed extrusions in a max base mesh.

to answer the welding question. select all the vertices in the mesh and in editable poly under edit vertices
press the weld button (not collapse) weld merges any verts inside a threshold which can be increased/decreased if you press the settings button next to weld. Its usefull to routinely do a weld threshold on the whole mesh while modelling to clean up any little errors that might have happened without needing to go through and search for them but obviously that could cause unwanted welding in places where verts are very close together. usually a threshold of .01 or something will only weld verts that are right on top of each other so you can safely weld everything without worrying.

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Thank you once again Tyson, I didn't know you could weld them all like that! I appreciate the tip!

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