Thank you for the detailed explanation. I think I now understand your needs better.
- Updating of CAD models
It can be certainly useful to update your CAD model as you combine it with anatomical shapes. We plan to implement real-time synchronization with selected modeling software (Blender and FreeCAD) so that if you modify your CAD model, the changes show up immediately in Slicer. This would make it easier to create an updated volumetric mesh whenever you adjust your CAD model.
- Mesh generation
COMSOL’s mesh generation capabilities are very nice, but you don’t need to use them, if you generate your volumetric mesh in another software. COMSOL can load volumetric meshes in COMSOL or NASTRAN format (see “Importing COMSOL Meshes” slide here). This is the approach that Materialise Mimics and Simpleware ScanFE use and you can do it with Slicer, too: save the volumetric mesh as a VTK unstructured grid file (.vtu) and convert it to COMSOL or NASTRAN using FEconv. With a little work, FEconv could be added to Slicer as an extension and then you could save the volumetric mesh directly from Slicer to a variety of FE mesh file formats.
- Converting surface meshes NURBS/BRep solids
We are using SolidWorks and Autodesk Fusion 360 and they of course cannot automatically convert meshes to solids (NURBS or BRep). This is similar to how vector graphics programs deal with bitmap images: they can load them, nicely display them, and can convert to vector graphics - kind of, with some data loss.
Reverse engineering tools sometimes work for simple geometric shapes (Fusion 360 sets the limit at about 10000 facets), but if you want to have usable result then you have to re-create the object manually (see for example this tutorial).