[ODE] Better way to find 'Desired Velocity'

[George Birbilis]

> 3) I run into a special case for: if you can get there in one
> timestep, you can overshoot in one step and then overshoot back then
> next step, and you get jitter.

that's why you're supposed to slow down as you approach your target and 
speed up when target is still far away

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George Birbilis (birbilis at kagi.com)
http://www.kagi.com/birbilis
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