Importing CAD file in GMSH

Hi, I have a question regarding the SPIS geometry, mesh modules, and GMSH. I have a step file (built in Autodesk Inventor) that consists of a sphere with a patch and a bigger sphere that will be the external plasma boundary. I tried to upload it directly in the geometry module and the conversion was successful but once in the group editor, I couldn’t define the correct components of the geometry, meaning that only the external boundary and the plasma volume are defined but not the internal boundary. I tried to upload it in GMSH to define such boundaries but it doesn’t allow me to define the spherical surfaces. Is this a problem on the Autodesk side or the SPIS/GMSH side? How can I define a spherical surface in such a way that SPIS can read it?

To upload the file in GMSH I created a new file with the geo extension and added the step geometry by means of the “merge” command. Is this the correct procedure to do this task?


In the Gmsh editor, did you define physical groups for the internal boundary? Defining physical groups then allows you to later apply material properties to these surfaces.

Hello! Maybe you know about this error “ThreeDUnstructVolMesh.autoThinSurfaces: volume mesh surface has no neighbour cell and duplicates a surface with no neighbours”? I import CAD file from solidworks, then i define pyisical groups in GMSH, make mesh - i receive a good 3d mesh, but SPIS have this error .

Hi Miles, I couldn’t define the physical groups because GMSH didn’t recognize my uploaded surfaces. I can do it with some surfaces, but it seems like it has problems with spheres and cylinders. Any idea of where the problem could be? Or do you have any advice for the conversion process .step → geo?

In those cases, I cannot define either geometric or physical surfaces.

Hi Marianna,

Unfortunately, I have never tried to import a .step file into GMSH. Spheres and cylinders are fairly easy to make directly in GMSH. Have you tried making your spacecraft geometry directly in GMSH?

Sorry I can’t be of more assistance with importing the geometry. If you are able to share the .step file, I can try importing it into GMSH and see what happens.