Convert a NURBS surface into Bezier patches

Rhino Rhino for Windows
1

Hi guys, I am new to this software and I wanted to know how to convert a NURBS surface(circular cylinder) into a number of Bezier patches.

2

ConvertToBeziers

A cylinder in Rhino is usually a polysurface, and Explode will need to be used first to convert the polysurface into individual surfaces.

Be aware that a cylinder in Rhino is a rational NURBS cylindrical surface with trimmed end planar surfaces. the result of ConvertToBeziers will be rational Bezier surfaces from the cylindrical surface and untrimmed Bezier surfaces from the ends. If non-rational Bezier surfaces are needed the cylindrical surface will need to be rebuilt as a non-rational NURBS surface first. Rebuild or RebuildUV can be used with the user deciding on the number of control points needed to achieve the desired accuracy. The end surfaces can be recreated as untrimmed surfaces using EdgeSrf after rebuilding the cylindrical surface.

3

Hi David, thanks for your suggestions. your suggestions really helped me.
coming to the point:
My research topic is on calculating the radar cross section. I came across many papers in which the bodies are represented as Bezier patches as they are more numerically stable than the nurbs.
I followed the points that you stated and I have given no of control points in U and V direction. my doubt is how do I know whether the cylinder is converted into Bezier patches or not?

4

Bezier patch is exactly equivalent to a single span NURBS patch. Number of spans = number of control points - degree.

I don’t know why a NURBS surface with 3 spans in one direction and 2 spans in the other direction would have different numerical stability than an equivalent set of 6 (3 x 2) Bezier patches for example.

My belief is most of the claims about the superiority of single span / Bezier either are based on false comparisons or are just unsupported opinion. However there are advantages in some situations to using only single span / Bezier. An in depth comparison of single span surfaces / Bezier patches with multispan NURBS surfaces is a topic for another thread.