Curve Slice brush creates wide poly line

[metalforger71]

Hi, my work is enlarging digital sculpture for bronze casting. I part clients models and CNC mill the parts in foam as an armature for clay. When parting the model for milling, the curve slice tool leaves a wide line of new poly. (see pic) So before I close the hole up from the parted model, I have to make sure I select both poly’s first, and the combine them all into one poly and save the part. Otherwise this missing information would make assembly difficult.

Is this normal? Shouldn’t the curve slice tool separate the poly’s in a clean line? Or is there a better workflow I should be using ?

Thanks.

[Spyndel]

HI @metalforger71 !

I’m not sure that I understand the issue from your screenshot.

The slice curve brush will slice through the mesh where you draw it, creating a new edge loop. However, polygons with greater than 4 points cannot exist at any time–even temporarily–in ZBrush. So it must insert edges to force quads and tris out of the operation. You can avoid this by slicing the model in such a way that you’re slicing cleanly through a poly loop that results in 4 point quads on either side.

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You may be referring to the new polygroup the slice curve brush is creating there? Slice curve will only create a new Polygroup up to the border of an existing Polygroup. If there is only a single polygroup on the shaded side of the slice line, it will be overwritten. However if there is another polygroup border in that direction, it will only create a new polygroup up to that border. This is probably what resulted in the the new, thin polygroup in that location.

Working with polygroups is simple if you have committed the polygroup visibility shortcuts to muscle memory. It should only take a few clicks to isolate the two resulting poly groups and merge them into a single group. If you have not yet done this, you’re likely to struggle with basic mesh management in ZBrush:

https://help.maxon.net/zbr/en-us/#html/user-guide/3d-modeling/modeling-basics/polygroups/polygroups.html?Highlight=polygroups

You can prevent Slice Curve from altering the Polygrouping at all by first masking the target mesh. Then the brush will slice but not regroup.

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However, there is a better way to do all of this in Zbrush 2024

Instead, in ZBrush 2024 use the Knife Curve brush, and set Brush> Clip Brush Modifiers> Split to Parts to be “ON”.

Now when you cut through the mesh with the Knife brush, it will cut the mesh into two exact pieces on either side of the cut, and mask one side. Then you can move one portion of the mesh away from the other, OR split it into a new subtool with Subtool> Split> Masked/Unmasked.

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If I’m completely missing the problem, please document in greater detail and clarify.

Thank you!