ZBrushCentral

3D printing Zbrush scale and transform

ZBrush Usage Questions
#1

I’m working with some medical skull models from mimics. I first dynamesh them in zbrush, then decimate, then export either with the stl plugin, or export to obj. I keep my original file from mimics untouched as a reference in Rhino, and when I import the zbrush model it has always been centered and scaled down - I then have to manually try to match the scale of my original model in rhino.

Is there a way in zbrush to make sure that the model isn’t transformed or scaled? Also I can’t seem to find a reference anywhere on what units zbrush is using for measurement. I’ve been using mm in rhino so the scale issue’s could just be because of that.

thanks

#2

ZBrush doesn’t use any specific scale. I think the only way you can export with scale is via the 3D Print Exporter plugin.

#3

Check in Tools: Import and Tools: Export
I find when I import an obj, zbrush will import it with the appropriate scale and offset settings needed to export it back correctly. If you alter these values (such as setting the scale to 1 and offsets to 0), then you could easily make zbrush force the mesh to be smaller and centered on export. So try and keep those at whatever numbers are set during import.

Also make sure to freeze / zero off the transforms of the model in your 3d program before exporting the OBJ to zbrush, as that can also cause the OBJ you’re working with to become smaller and centered as well.

As for printing and scale, you pretty much specify the dimensions of the bounding box in either inches or mm

#4

I do a lot of work with scan data into zbrush and back out for 3d printing.

I’ve run into some issues with scaling between Zbrush and other programs. So I created a cylinder that’s exactly 100mm diameter and 10mm in height. I then saved this as an .obj and a .ztl file.

The scaling issues seem to be fixed when I insert the 100mm ring along with the other subtools. It also becomes my checking point when transferring 3d models into other programs or getting them ready to print. I can double check the ring’s diameter and make sure it’s 100mm. If it is then my model has scaled appropriately.

I usually don’t like using the 3d exporter. Instead I prefer to export as an .obj (that is after I’ve created a duplicate to be decimated first). I found the 3d exporter units to vary. With my 100mm ztool file I have to set the 3d exporter units to 10.

The .obj file is 3.5 mb and the .ztl file is 635 kb. I believe this 100mm ring is correct based on the Zbrush defaults. At default each Zbrush unit is 1mm. If it doesn’t show up as 100 (or very very close as the transpose tool doesn’t always grab the end vertices) then you may need to adjust your transpose units in your preferences.

I can send you the .ztl and .obj file if you’d like.