could you please help me?
i'm at the stage of writing a surface interrogation program where everything
is in place and it should all work.
but, for some reason my unit normal calculator is giving me incorrect
I think the problem lies in my derivatives of the B-Spline basis function
(i'm using NURBS).
could anyone point me in the direction of a correct, working version of the
p.s. just to make sure i'm not being stupid:
to calculat the normal at a point on a NURBS surface, do the cross product
of the two tangent vectors.
to get these tangent vectors (one for u and one for v(the paameters)) you
apply the same NURBS formula as to find a point but replace either the u or
v basis functions with its derivative.