2 curved surfaces of the same object intercept in the middle, how to separate?

Support Modeling
1

It’s the face and the mouth cavity which intersect at a small area.

How can I push back the internal one, or pull the external -only???
That is the question…

surf_inters

2

First, you need to retopologize, there’s so much overlapping geometry in the middle there and no flow, that is going to give you no end of problems (including this one)

To your question- if you want to separate these two objects to work on them separately, select all with A and then press P. Choose “By Loose Parts”

3

You can mask out the middle part with mask expand, invert the mask and finally sculpt (subtractive) on it.

4

Thanks, I know about retopology, that’s my next step after I finish sculpting, I’ve done this in the past manually for perfection, but I recently tried automatic software and it works well enough.
Both surfaces are from the same object like I wrote in the title so your suggestion doesn’t work.

5

Thanks, I did a search about mask expand and I think it appeared in v2.93 while I can only use 2.92 (win7).

6

I finally found a way:

  • In edit mode I selected a few faces of the internal surface from outside with the circle,
  • used Ctrl + Numpad + to expand the face selection radially until it covered enough area of the internal surface,
  • inverted the selection
  • hit h to hide everything else
  • In sculpt mode I used the inflate brush with a positive action (because it acts like a negative for internal surfaces) in order to deflate the internal surface a bit and stop intersecting.