nrbdeval

 NRBDEVAL: Evaluation of the derivative NURBS curve or surface.

     [pnt, jac] = nrbdeval(crv, dcrv, tt)
     [pnt, jac] = nrbdeval(srf, dsrf, {tu tv})

 INPUTS:

   crv    - original NURBS curve.

   srf    - original NUBRS surface

   dcrv   - NURBS derivative represention of crv

   dsrf   - NURBS derivative represention of surface

   tt     - parametric evaluation points
            If the nurbs is a surface then tt is a cell
            {tu, tv} are the parametric coordinates

   pnt  - evaluated points.
   jac  - evaluated first derivatives (Jacobian).

 Examples:
 
   // Determine the first derivatives a NURBS curve at 9 points for 0.0 to
   // 1.0
   tt = linspace(0.0, 1.0, 9);
   dcrv = nrbderiv(crv);
   [pnts,jac] = nrbdeval(crv, dcrv, tt);