# Ellipsoid definition and it's gradient

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I've been readying this tutorial http://www.gamedev.net/reference/articles/article2426.asp and found it very useful. I don't know what the "gradient" is which he uses in the appendix A: The ellipsoid's surface normal will point along its gradient. I also would like to know what x, y and z is in the definition of an ellipsoid ( (x^2)/(Sx^2) + (y^2)/(Sy^2) + (z^2)/(Sz^2) = rad^2 ).

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 Original post by HannesnisulaI've been readying this tutorial http://www.gamedev.net/reference/articles/article2426.asp and found it very useful. I don't know what the "gradient" is which he uses in the appendix A: The ellipsoid's surface normal will point along its gradient.
Clicky. the gradient referred to is that of the field defining the implicit surface.
Quote:
 I also would like to know what x, y and z is in the definition of an ellipsoid ( (x^2)/(Sx^2) + (y^2)/(Sy^2) + (z^2)/(Sz^2) = rad^2 ).
The coordinates of any point on the ellipsoid.

From your questions, it sounds like you don't quite understand the concept of an implicit surface. See here for more information.

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