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Boresight
06-21-2001, 06:16 AM
In gluNurbsCurve() and gluNurbsSurface you give a sequence of knots.

What exactly are knots in a NURBS?

micheal
06-21-2001, 08:47 AM
Knots are used for define the B spline functions. They should be a nondecreasing
sequence. If you would like your Nurbs Curve
passed by a Control Point(for example, let it start from the first Control Point and end at the Last Control Point), the corresponding Knot should have multiplicity n (n is order of your Nurbs curve.). You can control the
shape of Nurbs Curve by define different
multiplcity number, which you can refer
to the Book:
(The systems Programming series)
Computer graphics:Principles and Practice,
Foley, van Dam, Feiner Hughes

An example:
If the order of your Nurbs Curve is 3,
and you have 8 control points,
Then the knot sequence can be
0,0,0,1,2,3,4,5,6,6,6
which will make out a curve that passes by
the first and the last Control Points.


Originally posted by Boresight:
In gluNurbsCurve() and gluNurbsSurface you give a sequence of knots.

What exactly are knots in a NURBS?

Boresight
06-21-2001, 09:11 AM
Thanks so much, it's I need know