This seems like it would be right, but just wanted to make sure, since it''s more of a "that seems right" instead of something backed by actual equations. If I have a oval with height 1 and width 2, would that be just like taking a circle and scaling it so that it''s size 2. Or rather, could I do quick collision detection by simply taking the position of an object and finding the X and Y distance from the center of a circle. Then I''d divide the X distance by the scale of the circle (the distance of the left or right side from the center) and do the same with the Y. Then I could just do a simple collision detection against a sphere. I''m thinking this would work, but just wanted to be sure. --Vic--

Well, the equation for a circle is:

x2 + y2 = r2

And the equation for an ellipse is:

(x2 / a2) + (y2 / b2) = 1

A circle is basically a specialized ellipse, where a and b are 1. So technically, an ellipse could be considered a scaled circle.

The answer is yes. Technically, if you perform an affine transformation (like scaling on one axis only) on a circle, the result is an ellipse. To intersect something with an ellipse, you can do an affine transformation to make your ellipse a circle and then intersect with the circle. If you need the intersection point, you have to undo the transformation.