[PyOpenGL-Users] a question about nurbs and the glu routines.

[noah l. <nl...@ea...>]

Hi everyone,=20

disclaimer: I'm just learning both python and opengl, and I may be
breaking off more than I can chew here.

Python 2.2
windows 2000 sp2
pyopengl 2.0.0.44

I'm using python and opengl to do more abstract, creative interactive
environments in the hopes of integrating these studies into my chosen
field, architecture. The program here is a single nurbs curve that is
created from random points generated for each frame.  I was able to
modify the red book nurbs curve example with evaluators, but now I'm
trying to use the glu routines (I'd like eventually to be able to do a
whole bunch of these curves).

two issues:  the first one(and biggest) is that the thing won't work.
the relevant code follows...

###nurbs4.py=20

# not sure what to put in knots... ascending floats, 7 terms
# doesn't seem to make too much difference...

controlpoints =3D []      # I have a basic routine to pack this  =20
knots =3D [0.0, 0.0, 0.0, 1.0,2.0,3.0,4.0] =20
                       =20
nurb1 =3D gluNewNurbsRenderer()    =20
...<snip>
def InitGL():
...<snip>
    glEnable(GL_AUTO_NORMAL)
    glEnable(GL_NORMALIZE)
    gluNurbsProperty(nurb1,GLU_SAMPLING_TOLERANCE,50.0)
    gluNurbsProperty(nurb1,GLU_DISPLAY_MODE,GLU_OUTLINE_PATCH)=20
def DrawGlScene():
...<snip>
    gluBeginCurve(nurb1)
# I've tried all the kinds of types for glNurbsCurve,
# with little effect.   =20
    glNurbsCurve(nurb1, knots, controlpoints, GL_MAP1_TRIM_2)=20
    gluEndCurve(nurb1)

### end code fragment

the error message I get follows:
Traceback (most recent call last):
  File "nurbs4.py", line 85, in DrawGLScene
     gluBeginCurve(nurb1)
OpenGL.GLU.GLUerror: [Errno 100259] can't draw pwlcurves

the second problem occurred as I tried to put in an error correction
callback to read GLU_NURBS_ERROR (not GLU_ERROR) and couldn't get
either of them to work as a proper error. I know that GLU has
deprecated the older one in favor of the new one, and I'm using the
most recent version of pyopengl...

In any case, if you can get me on track with the first problem, I'll
be mightily appreciative.

thanks in advance,
noah luken