GNURBS

Interactive manipulation of NURBS surface/curve

Description

For use with the NURBS toolbox, GNURBS allows the user to have an intuitive manipulation of a NURBS surface/curve via control points.

example:
% Graphically manipulate test surface
gnurbs

• MATLAB release: MATLAB 7.3 (R2006b)
• Other requirements: NURBS Toolbox http://www.mathworks.com/matlabcentral/fileexchange/loadFile.do?objectId=312&objectType=file

[Per Bergström]

A professional NURBS program!

[Tim Davis]

There are some very unstable numerics in this code that need to be fixed. For example, you compute R = inv(M) and then only use R to multiply with T=R*up. Never multiply by the inverse. Use T=M\up instead. In addition, there is a very odd use of "det" to solve a system. det is extremely numerically sensistive and should never be used to solve a system.

[Daniel Claxton]

Since it's not immediately obvious. It should be mentioned that I updated GNURBS in response to Dr. Davis' comments.

[Joe]

I tried your script for a simple circle e.g. mycirc = nrbcirc(20) and then do

gnurbs(mycirc,res)

where res = [100,100] (just an example)

Why does the curve change when I start moving the control points? Also, is there a way to print out the updated control points, weights, knots, etc? Thanks.