How to get the weight and derivatives of a point wrt to a control point?

Hello experts, thanks for the amazing library.

I have a NURBS surface and N control points. Now I want to evaluate a point P(u, v). I need the weight w and derivative wu, wuu, wv, wuv and wvv wrt to each control point. Has anyone got an idea of which function should I use? Thanks.

Are you writing a plug-in for Rhino or Grasshopper, or stand-along software?

Hi, I am using the OpenNurbs library in my own c++ project.

Note : openNURBS is an open source toolkit for only reading and writing 3DM files. Our full-featured development platform is provided in the Rhino SDKs.

Hi David, do you mean I need to use Rhino SDK rather than Opennurbs?

The Rhino SDK is for writing Rhino and Grasshopper plug-ins, not standalone code.

You will need to find a different library or write your own functions based on the NURBS equations. The NURBS Book by Piegll and Tiller is a good reference.

Okay. Thanks for your advice. That is very useful!