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Scale units Maya to Zbrush

ZBrush Usage Questions
#1

Hi,

Now I know this is a stupid question and it has been answered indirectly in other places but I can’t find the detailed answer I need so apologies, but…

What unit scale should I use in maya to goz between maya and Zbrush.

The only answer I managed to find elsewhere said that scale is irrelevant to Zbrush because it uses pixols (whatever they are), but that doesn’t seem right to me, because, for other pipeline reasons, its useful for me to work in centimetres in maya. But that means that when I import a character into Zbrush that’s about 200cm high. Then some of the tools in Zbrush become really difficult to work with. ie. Dynamic brushes are tiny and the transpose scale becomes ineffective. If I work in metres, then the dynamesh resolution is really low.

I know that there’s a scale multiplier slider in the export panel, which helps a bit. But if I want to create the base mesh in Maya, then it seems to me I’m stuck with importing either metres or centimetres, niether of which wrok in all circumstances.

Is there not some sort of scale unit or import multiplier in Zbrush?

The best way I can think to do it would be to import in metres or centimetres and then use the geometry>size to scale up or down be a factor of 10 to make the model workable in zbrush.

Is that really the best way to do it or have I missed something obvious?

Thanks in advance.

#2

Many 3D model file formats, such as OBJ, do not have a unit of measure but simply use a generic unit so that a vertex with a position of 1,1,1 is one unit away from the origin along each axis. It’s then up to the 3D program to decide what that unit represents and in Maya the default is a centimeter.

ZBrush just uses the generic unit so you can call it what you want. However, there are a few things you need to be aware of.

  1. ZBrush will scale very small or very large models so that they are a suitable size for the sculpting brushes to work well. You can tell when this has happened by looking at the Tool>Export>Scale slider. However this doesn’t affect how the Transpose line measures the size.

  2. If you import an OBJ into an existing model in ZBrush then it will be scaled based on that model. To make sure that this doesn’t happen you need to select the PolyMesh3D Star tool first and import the OBJ into that.

  3. You can set up the Transpose line so that it reads any measurement unit you want. You can also set it up so that the unit you choose is based on a fraction or multiple of the generic unit. You can set this up in the Preferences>Transpose Units sub-palette.

  4. Using GoZ between Maya and ZBrush shouldn’t change the scale, so measurements you make in ZBrush using the Transpose line will be correct when you send the model back to Maya.

Attached are a couple of example OBJs for you to try. If you import them into Maya then they will be 2cm square and 100 cm square. When you import them into ZBrush remember to select the PolyMesh3D Star first. You’ll see that they look the same in ZBrush but the Transpose line will give different measurements.

Attachments

Maya-2cmCube.jpg

#3

Hi Marcus,

Thanks very much, that did the trick.

Terence