ZBrushCentral

How do I use the topology brush to get geometry only on the surface of a model?

ZBrush Usage Questions
#1

I want to add mesh as guides for gluing multiple 3D prints together.

The model has to be split to fit the printers build volume. It’s hard to keep the parts aligned while the glue sets.

I can build guides using the topology brush, with a small amount of thickness, thus building a tab which will overhang the adjacent subtool. If I put a few tabs around the circumference, the two printed parts will align. After the glue sets, I can sand off the tabs.

This only works if the tabs sit on the surface. If they have depth into the model, the overhang won’t slide over the second part. It also causes problems when I make a shell.

I can’t figure out how to just add the mesh to the surface. The brush adds an equal amount to the front and rear face (the inside and the outside of the model) so the tabs intrude on the adjoining part.

Backface masking doesn’t work.

Any ideas, or an alternate workflow?

Thanks in advance!

#2

Set your Draw Size to 1 before clicking on the new topology to make it into a mesh. This will ensure the new mesh has no thickness. Then switch to the ZModeler brush. With the cursor over a polygon, press the spacebar and select QMesh from the Actions and All Polygons from the Target. You will then be able to click+drag out a little thickness.

Also, with 4R8, you may be able to use the Boolean feature to get a perfect fit.

#3

IF I understand what you want, the Subtool > Extract function may prove easier to use for this purpose.

In this case, simply mask the portion of the mesh you wish to generate a guide around, then go to tool > subtool > Extract, and hit extract. It will generate a thin piece of geometry on the surface that you can preview on the model, and adjust the thickness and other settings until you are happy, and then hit “accept” to generate it.

By default, it will rest only on the surface and above of the target mesh, as long as the thickness setting is positive.

#4

I just got back to the studio and tried both.

The “extract” workflow is very simple, easy to control, and works just as I had hoped.

Thanks to both of you!

Best…

Rob

#5

This works well, except that it creates a symmetrical mask, with the mask on both the facing and rear surfaces.

Symmetry is off, and backface masking doesn’t fix it.

Since the topology isn’t symmetrical, the mask on the rear side isn’t in the appropriate place.

How do I mask only the front surface? I have this issue with all masking brushes, not just the rectangle brush.

Thanks again, in advance!