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Sub-D <-> Parasolid
It's not Onshape, but…
The latest beta of Plasticity (Parasolid based) has added a high-quality OBJ import/conversion tool, and a bridge to/from Blender. It converts sub-d to NURBS with G2 even at the star points. I'm not a sub-d person, but if you have workflows where you need to bring sub-d into Onshape, it could be worth a Plasticity Studio license just to do this.
[yes this demo video is auto-dubbed in English, but worth watching]
Simon Gatrall | Product Development, Engineering, Design, Onshape | Ex- IDEO, PCH, Unagi, Carbon | LinkedIn
Comments
When he says the surfaces are "Sub-D like" and shows examples of fillets and other surface intersections booleaned right over top of some of those "Sub-D" patches it makes me think he's actually got some T spline surfacing happening in there, not B spline. If that's true I'm wondering whether that's a thing the parasolid kernel now supports natively after Autodesk's patents expired or if that's done via xNURBS. Huge news if it's a parasolid thing.
Derek Van Allen | Engineering Consultant | MeddlerThe input is sub-d, the output is NURBS, but you can also round-trip to Blender and do more sub-d stuff there.
It's based on something that Plasticity licensed from a third party called "Polysplines". Nick Kallen (owner/founder/lead-developer) says "it's a generalization of the b-spline surface". It turns the .OBJ into degree 3 and degree 6 NURBS surfaces, with G2 continuity at the joints.
Simon Gatrall | Product Development, Engineering, Design, Onshape | Ex- IDEO, PCH, Unagi, Carbon | LinkedIn
Here's a paper on the research that Polysplines came out of:
https://www.cise.ufl.edu/research/SurfLab/papers/23PolySpl_TOMS.pdf
Simon Gatrall | Product Development, Engineering, Design, Onshape | Ex- IDEO, PCH, Unagi, Carbon | LinkedIn
Derek Van Allen | Engineering Consultant | Meddler