Moving an object on a path in AS2

Lately I’ve been working on a custom solution to animate movie clips via Actionscript. As I needed more flexibility than the Tween class provides, I’ve thought about writing my own engine and started studying Bezier curves.

Fortunately I discovered Path.as, written by Ivan Dembicki. Basically you give it a number of control points and it builds a several quadratic Bezier curves that form the desired path (a quadratic curve needs three control points). Then you can get the length of the path and find the coordinates of any point on the path.

You can also find some more information on Bezier curves by reading about DeCasteljau Algorithm with a little pseudocode. If you’re interested on the subject, Jim Armstrong has a number of entries on spline curves in his blog, with source code.