John VanSickle wrote:

> Let me point out here that re-calculating the new position first, with the
> formula P' = P + Vt + At^2/2 yields less inaccurate results.  This still
> results in an accumulating degree of imprecision; modifying the equations
> to include third-order behavior reduces the imprecision; a bit of drag
> (the cV factor you mention above) will reduce the wild thrashing that can
> result from the accumulating errors.
>

Never implement undampened springs.  They will explode with small accumulating
errors.

> For those interested, feed "Runge-Kutta" into your friendly
> neighborhood search engine.  Google registers over 3000 hits.

Tough parts are collision detection (especially particle-particle collision),
continuous contact, and rigid bodies (requires calculating center of mass,
torques and 3D orientations).

David Buck
dav### [at] simberoncom

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