GMSH integration yields UContinuity error

[bragostin]

Dear CQ community,

Using

cadquery @ git+https://github.com/CadQuery/cadquery.git@153ed3f667911e909ba8b93bddd297defc7cd42f
cadquery-ocp==7.7.2
gmsh==4.12.2

the following simple code adapted from #1346

import cadquery as cq
import gmsh

FD_new = cq.Workplane("YZ").center(-2.5, -10).rect(5, 20).extrude(100)

gmsh.initialize()
gmsh.option.setNumber("General.Terminal", 1)
topods = FD_new.toOCC()
volumes = gmsh.model.occ.importShapesNativePointer(topods._address())
gmsh.model.occ.synchronize()
gmsh.option.setNumber("Mesh.Algorithm", 1)
gmsh.option.setNumber("Mesh.MeshSizeMin", 1)
gmsh.option.setNumber("Mesh.MeshSizeMax", 5)
gmsh.model.mesh.generate(3)
gmsh.write("FD_new_mesh.msh")

yields this error

Error   : OpenCASCADE exception GeomAdaptor_Surface::UContinuity
Traceback (most recent call last):
  File "/home/issue_gmsh.py", line 11, in <module>
    volumes = gmsh.model.occ.importShapesNativePointer(topods._address())
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/chbrago/cadquery/lib/python3.11/site-packages/gmsh.py", line 8627, in importShapesNativePointer
    raise Exception(logger.getLastError())
Exception: OpenCASCADE exception GeomAdaptor_Surface::UContinuity

any idea what is wrong here?

[jmwright]

@bragostin Did you install CadQuery via pip? It would be interesting to see if using conda fixes the issue, and also if using an older version of OCP helps (to test for a regression in OpenCASCADE/OCP. If neither of those help, maybe you can check with the gmsh community to see if there is any extra object debugging that can be done on that side?

[bragostin]

@jmwright Yes it was a pipinstall.
Reverting to cadquery-ocp==7.7.1 does not solve the issue.
Export in a STEP file and importing via gmsh.merge function works.
I will try with a conda install next.

[bragostin]

@jmwright with a fresh conda install conda create -n cadquery -c conda-forge -c cadquery cadquery=master cq-editor=master and gmsh==4.12.2 (same as pip install) the issue disappears.
So the problem comes from the pip install it seems.

[adam-urbanczyk]

Then it is likely an ABI compatibility issue. conda-forge avoids this by having a well defined toolchain. That is not the case for pip, everyone can choose a different compiler/flags.

[bragostin]

@adam-urbanczyk thank you! Anything that can be done beyond using conda? Like raising the issue with the gmsh team?

[adam-urbanczyk]

You could try compiling all packages yourself. I don't think this is a gmsh or ocp packaging bug.