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Maya LT -> ZBrush 2021 back to Maya LT produces weirdly rounded geometry

ZBrush Usage Questions
#1

Hello all,

I’m a total beginner at both Maya and ZBrush, so it’s highly likely the answer to this is simple. I’m starting out with a shape I made in Maya LT. It’s basically a weirdly shaped plane, so it only has polys facing one direction.

I’d been learning that ZModeler can add depth to planes pretty easily compared to doing the same in Maya, so I thought it would be a good opportunity to try out the Maya->ZBrush->Maya workflow (since I’m using Maya LT I can’t use GoZ)

So, the plane exported from Maya and into ZBrush easily enough. I was able to add the depth I wanted easily with the ZModeler brush, and then I exported the tool back into Maya format. However, when I re-import it to Maya it has all this really odd rounded geometry to it that isn’t present (or at least, isn’t visible?) in ZBrush.

Am I doing something wrong? Is this a problem on the ZBrush side with the export or the Maya side with the import?

Hopefully the image attached will help illustrate what I’m talking about.WeirdRounding

#2

Hello @Wyldfire

I can explain in general what is probably happening here, but much of this will come down to your knowledge of working in Maya. I’m not a Maya expert. It’s possible someone here who uses that particular workflow may notice the thread and help, but you’d probably have better luck with a resource devoted to Maya.

In Zbrush, when you subdivide low poly geometry, by default a smoothing effect is applied to the mesh. If this didn’t happen, the mesh would retain the faceted look of the low poly geometry, even at high levels of subdivision. Sometimes this is exactly what you want to happen! For instance in your case here, you have a structure without any curves or rounded features–all planar surfaces. You could go to Tool> Geometry> Divide, and disable the SMT (subdivide smooth modifier) button next to the Divide button. Then when your mesh is subdivided, it will retain the look of your low poly geometry even at high levels of subdivision.

However, many meshes have a combination of curved and planar features. In these cases, you must mark the edges you wish to stay hard-edged through the subdivision process. In Zbrush, this is done with Creasing. Any edges with a crease tag applied will stay hard edged–everything else will be smoothed.

So what is probably happening here is that you are subdividing your mesh without the equivalent feature applied in Maya. Maya resources and other Maya users may be able to instruct you in how to accomplish this in Maya, and may even have tips on the best way of working back and forth between the two programs to make establishing edge creasing in that program easier.

Good luck! :slightly_smiling_face:

#3

Hi @Spyndel

Thanks for taking the time to look at this. The suggestion of looking at SMT was a good one, and indeed it WAS enabled. Sadly, disabling it and redoing the operation didn’t change anything. I suspect that it was always performing the operation without smoothing, certainly it doesn’t look smoothed in ZBrush itself.

So I stated to suspect the export process. I was using Export Tool -> Maya format, since I was intending to import it into Maya after all. That’s what was producing the weird rounded shape above. But, ZBrush gave no options for that format, and Maya gives very few on Import (mostly about how to resolve namespaces etc)

But, I decided to try FBX export from ZBrush instead. That pops up an options dialog. I tried it with default settings and got the same result. But on the second try I took a long look at the settings. The “SNormals” option apparently means “Smooth Normals” - turning THAT off produced the correct planar shape (now with thickness!) upon import to Maya!

I’m not sure if this is a quirk of have an entirely planar object in ZBrush which surely is atypical, or if the “Maya” exporter is just best avoided. But I’m glad to have a solution.