ConvertToBeziers (both v5 and v6)

ConvertToBeziers removes the trims from surfaces. Splitting surfaces at iso-params with “shrink” option is a work around at the moment.

It would be convenient if the ConvertToBeziers could retain the trims.

Hi Rajeev - can you give an example of why you need this?



Hi Pascal, I am trying to figure out a workflow where the output is all single span Beziers… a la ICEM Surf output … which many of my German friends in the automotive industry considers as a requirement for “Class A” surfaces. Personally I don’t prescribe to their views.
For me a multi span polynomial surface of degree 5 will serve the purpose adequately. More about my views on the subject at

For most parts, I can create such “Class A” surfaces. But I am stuck at analysing the continuity between surfaces. I wish we had something like _Gcon for surfaces or a global check to see if the surfaces are at least tangent continuous to each other. For the time being I have to transfer the geometry to either ICEM Surf or Alias to check the continuity. I am experimenting with grasshopper to create a continuity checker… like

I believe there is no standard way to calculate curvature and higher order continuity ( many vendors calculate it differently) and that it is a matter of designer taste or perception.

Coming back to your question… ConvertToBeziers is a quick and easy way to satisfy the “Class A” clients, if the trims could somehow be retained.

I see, so, the idea is you make your objects as best you can, and then ConvertToClassA, sorry, I mean ConvertToBeziers and send it out, right? My guess is retrimming is not technically difficult but realistically won’t actually happen any time soon… but I could be wrong, I’ll add it to the pile.


A manual work around is to DupBorder before converting to Beziers. After conversion use the duplicated border to trim / split and delete the Bezier surfaces.

Thank you very much… Incidentally, Rhino untrims the surfaces even if the input surfaces are Single Span Beziers.