Solid difference problem

Hi there,
I’ve a problem with solid difference.
The code is very simple, and I can’t understand why doesn’t work. The surfaces are quite complex, but with another surfaces more complex it works.
Basicly I convert meshes in polysurfaces, extrude them and than perform the difference. Unfortunately the difference return the same starting solid.
I’m doing something wrong?

Thanks in advance
Giovanni (724.5 KB)

difficult to say :slight_smile: I crashed my GH 5 times without reaching a non-working solution :slight_smile:

would it be useful to project the vertex points of upper mesh into the lower mesh, and if there’s nothing they can be projected into then just move them -Z by 10’000 ?

in theory this should “rebuild” just the bottom part of your boolean subtraction: (729.2 KB)

[btw: top mesh has been tri-remeshed]