CURVEDERIVCPTS: Compute control points of n-th derivatives of a B-spline curve.
 
 
 usage: pk = curvederivcpts (n, p, U, P, d) 
        pk = curvederivcpts (n, p, U, P, d, r1 r2) 
 
 If r1, r2 are not given, all the control points are computed. 
 
  INPUT: 
         n+1 = number of control points 
         p   = degree of the spline 
         d   = maximum derivative order (d<=p) 
         U   = knots 
         P   = control points 
         r1  = first control point to compute 
         r2  = auxiliary index for the last control point to compute 

  OUTPUT: 
         pk(k,i) = i-th control point (k-1)-th derivative, r1 <= i <= r2-k 
 
 Adaptation of algorithm A3.3 from the NURBS book

Package: nurbs