NRBDERIV: Construct the first derivative representation of a
NURBS curve or surface.
Calling Sequence:
ders = nrbderiv(nrb);
Parameters:
nrb : NURBS data structure, see nrbmak.
ders : A data structure that represents the first
derivatives of a NURBS curve or surface.
Description:
The derivatives of a B-Spline are themselves a B-Spline of lower degree,
giving an efficient means of evaluating multiple derivatives. However,
although the same approach can be applied to NURBS, the situation for
NURBS is a more complex. I have at present restricted the derivatives
to just the first. I don't claim that this implentation is
the best approach, but it will have to do for now. The function returns
a data struture that for a NURBS curve contains the first derivatives of
the B-Spline representation. Remember that a NURBS curve is represent by
a univariate B-Spline using the homogeneous coordinates.
The derivative data structure can be evaluated later with the function
nrbdeval.
Examples:
See the function nrbdeval for an example.
See:
nrbdeval