You did not post the specific STL file that you wanted to convert to a "Nurbs solid".
I used a fairly simple STL for a mount for a 3M respirator cartridge, HEPA + Organic, filter + activated carbon, to a fan. (About 155 kb)
(The STL imported to MoI would be about 75,000 kb, a huge amout of overhead.)
It is just a flat slab (2 planar slab surfaces) with a few round holes, plus a cylindrical "nipple" for the cartridge.
Imported the STL to MeshLab, and saved as .OBJ.
Used ImportOBJ script to get the .OBJ file into MoI. (Did not try the OBJtoEDM script.) (About 450 kb) It is a large number of triangular faces with edges, mostly planar.
Then did a couple of hundred or so of MoI geometry commands to (begin to) get a NURBS solid. (Did not finish) It was a lot of work...
It might be easier to just start from scratch, or trace outline images...
It would have been helpful to have a script to get the perimeter of a planar mesh of triangular surface (edges).
This would not help for a 3D "dolphin" mesh.
There is a tool but I never had chance to used it, is tool you can buy via contact, and it's maybe for a developers, because I think is more like to the C3D kernel, but I'm not sure. https://c3dlabs.com/en/products/c3d-toolkit/b-shaper/
Anyway here some examples:
If the object is simple you can rebuild with many tools like FreeCAD.
I could not find a price for C3D B-Shaper, but a companion module showed $1000 per month, so I am sure that the program is way beyond my budget.
There are a few sites explaining some of the mathematical type steps used for the conversion to b-rep, (Segmentation, Normals, Curvatures...). It is not an exact science...
Also the program appears to be RU.
