Union of two Bezier surfaces

Hi all,

I have a query regarding the union of two bezier surfaces. Whenever I tried to union two Bezier surfaces, rhino converts them to poly-surfaces where I cannot get the information of control points.

Is there any way to join two bezier patches so that the resultant surface is still Bezier in nature?

Thanks and Regards
Sai charannath Dubba

with some limitations:
check help / documentation for more info.

what is the next step in your workflow ?
maybe post a file and describe what you want to achieve.
kind regards -tom


Hi Tom, Thanks for your input. But _merge surface again converted the Bezier surfaces to a single NURBS surface. But I wanted the surface to bezier even after executing the _merge surface. I am working on FEM on bezier surfaces.

As soon as you merge two BĂ©ziers, you get a Nurbs with 2 spans. A Nurbs is basically nothing else as a composite out of BĂ©ziers. If you want a BĂ©zier after merging, you need to reapproximate the surface again. This is simply often not doable, without the creation of larger deviation and loosing continuity to other surfaces. And of course this is because the (human) modeler decided to represent that part of the shape with two, instead of one, surfaces.Very likely for a good reason!
In other words, you want something rather impossible. Of course, you can try to increase the order of the new Bezier. Usually, In Rhino, there is a limit of the order to be 14 (?).

But as a fun fact, you can trick Rhino to create Bézier surfaces with an arbitrary order. E.g. of 100. Meaning you can create a Bézier with 100x100 points, but of course your polynomial is then also of that magnitude, which means that one single surface can slow down Rhinos’ performance significantly.