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Proportional cubic fit to 4 control points

The green vector indicates the best place for the central point on the magenta cubic fit to the first two and last two points.
Notice the instablity when two of the control vertices are close.
The red vector is a proportional bi-laplacian. It is more stable.
Press "c" to toggle between using the central point or ignoring it whren computing the fits.
Built with Processing by Jarek Rossignac on Sept 28, 2005.

Source code: betterFit pts