Hi I've searched the net for some time trying to figure out how to do this but couldn't find anything useful. What I'm trying to do is find the normal of an ellipsoid, given some point on the surface of the ellipsoid. An algorithm that doesn't involve calculus would be best EDIT: typo

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MSN: stupidbackup@hotmail.com (not actual e-mail) ICQ: 26469254 (my site) [edited by - nexius on June 6, 2003 4:57:35 AM]

If your ellipsoid is given by the equation x²/a² + y²/b² + z²/c² = 1, a normal is given by (x/a², y/b², z/c². Normalize it if you need it to be of unit length.

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Original post by Anonymous Poster
If your ellipsoid is given by the equation x²/a² + y²/b² + z²/c² = 1, a normal is given by (x/a², y/b², z/c²). Normalize it if you need it to be of unit length.

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Shouldn''t that be (x/a, y/b, z/c)?

I have another method. If you know the foci, find unit vectors that point to them from your point on the ellipsoid. The average of them is a normal. You probably want to change the sign so that the normal points to the outside.