ZBrushCentral

Morph Target Generation in ZBrush - Workflow

ZBrush Usage Questions
#1

Hi,

we are having the following problem:
I want to sculpt my Morph Targets / Blend Shapes in both XSI / Maya and ZBrush. In order to mix the programs I just use the standard way of reimporting my modified obj from Maya or XSI and at the lowest SubDLvl of my ZTool and voila the changes made there are applied to ZBrush.
Then I can continue working from there.

However I noticed that after I step up the SubDivision Levels and go down again even if I didn’t change the model in ZBrush at all the Lvl 1 Subdivision is different / has moved ALL the points of the ZTool a tiny little bit not just the ones that were changed from Maya. To make it clear:
Just after importing an obj in ZBrush at SubDLvl1 and stepping up the levels of the ZTool and then stepping down again, without even touching the model my previous Lvl1 from XSI or Maya and that from ZBrush are not the same any more!

This means that I CAN NOT sculpt any morph targets in Zbrush because not just the areas that will be changed will be affected but ALL points in the ZTool. I am guessing it is because ZBrush uses a different SubD Algorithm than the other programs which use mostly CatMullClark. This assumption is based on the fact that points that are in denser areas of the model don’t shift their positions that much.

Is there a way around that? Any help greatly appreciated…

M

#2

ZBrush uses Catmull Clark subdividing. Which also smooths the model, causing points to contract. When you go back down in levels, ZBrush’s multi-resolution modeling adjusts the points based on changes that have been made at other levels. That shrinkage is a change, so your model changes.

You can compensate for this by storing a morph target before you divide the mesh. Then when you return to level 1 you can switch to the stored target.

#3

Hi aurick,

thank you for the reply. Regarding your answer:
We are sculpting “partial shapes” in ZBrush e.g. left eyebrow or just for the mouth area and leave the rest untouched. In a way it seems to make sense that due to the multi resolution modeling the entire mesh changes. However this means that if I only want for example the mouth area to be affected / to export as a morph I have to go back to SubDLvl1 before exporting and then restore the previous mesh with the morph brush for everything except the mouth area / area I worked on.
Or in Maya / XSI use a Weight Map in conjunction with the exported BlendShape from ZBrush to affect only the mouth area / area I worked on.

If you can think of a better method please let me know.

Thanks for the answer.

M

#4

I’ve never used ZBrush in the way that you’re trying to. I’m afraid that I don’t really have any answers for you.

Although something you might consider trying would be to turn off Tool>Geometry>Smt before you divide the model. This prevents smoothing, which then prevents the model from shrinking at all.

To see what the model would look like smoothed, you’d then turn Transform>Quick off and set Tool>Display Properties>DSmooth to 1.

#5

Hi aurick,

I am afraid this is no option for us since the reason for us to sculpt the shapes in ZB in the first place is to see what the model looks loke with the displacemnt / the higher SubDiv Levels applied.

Thanks for your help though :+1:

M