Relation between extract thickness slider and scene units (mm)

When I use the transpose tool to measure I see mm and after exporting it to STL I have a good scale in mm. So in my scene 1U is 1mm. I have a few different scenes like that (from different people). Some scenes have got export scale but every scene is in mm and has correct export to STL with the correct dimension.

When I try to extrude from the mask then I have to put as thickness different values to get demanded mm thickness.

Sometimes 1mm is 0.04 extract thickness. Other time 1mm is 0.02 extract thickness.

Could you tell me how that thickness slider is related to scene units? What numbers are related to calculating correct mm values on the thickness slider? Because now I have to try on blind and calculate on paper what is quite a time consuming on bigger projects. I would like to create an excel spreadsheet to faster my work in Zbrush but I don`t know which values are related to that calculation.

Zrzut ekranu 2021-03-03 112152


I am not entirely sure, and it must to be confirmed. But it should depends of the scale of the model in Zbrush, if the XYZ Size is set to 2, then 0.02 will give 1 mm, and if the XYZ Size is set to 4, then 0.04 will finally become 1 mm, an so on.

when you import a model in Zbrush and use tool: deformation : UNIFY, the biggest axis will be come 2.0000 units and two other axis get relative size from that.

Hope it help !

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Thanks a lot for your help.

oh @mdesign I forget to mention that you can also use Precision Extraction, plugin.
you can download it from the resources page here :



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Thanks a lot.

So to summarize it:

  1. I may calculate extract thickness in mm by hand based on the longest edge of bounding box of current subtool (it will be some percentage or so)
  2. I may use Panel Loops thickness slider which is in the scene units (so mm in my case)
  3. I may use that wonderful plugin Precision Extraction.
  4. I may use new mesh extract brush (Mesh Project), intensity to 100, imbed to 100 to have 0.1U (mm) and after that change brush->modifiers->strength multiplier to multiply that value: f.e. 0.1U (mm) * 2.5 strength multiplier will give me 0.25mm.

Sweet!!! Thanks.

Do you know a way to inflate with mm values? It would give me the same final effect as an extract. Is that deformation>inflate also related to the longest edge of the bounding box?