finn@sunshine.cad.mcc.com (Chris Finn) (12/12/89)
Here is a problem to which I would like to know a fast and robust solution. Given a point (x1,y1,z1), and a surface represented by z = f(x,y), find the point (or points) on the surface where the normal points towards (x1,y1,z1). The spatial derivatives of f(x,y) are easily computed. The points and surfaces to which I would like to apply this are relatively non-pathological (i.e. f(x,y) != a hemisphere with x1,y1,z1 at the center). Thanks, Chris Finn MCC CAD Program, P.O. Box 200195, Austin, TX 78720 [512] 343-0978 ARPA: finn@mcc.com UUCP: {uunet,harvard,gatech,pyramid}!cs.utexas.edu!milano!cadillac!finn