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

- demodercrv % Copyright (C) 2003 Mark Spink
- demodersrf Demonstrates the construction of a general

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