On Mon, 21 Oct 2002 11:05:22 +0200, Christoph Hormann
<chr### [at] gmxde> wrote:

>I'm not totally sure about the terminology but i always thought the force
>based apprach is what's commonly called penalty methods.  What Rune uses
>is
>the classical impact rules based 'reflecting the velocity at the surface'.

Rune's approach is kinematic. A penalty function implies a dynamic
approach. However, the results are very similar.

Basically, a penalty function is such that it results in reversed
velocity in the next iteration. It always points normal to the surface
at the point of collision and it magnitude is such that the momentum
and kinetic energy of the particle are changed according to the laws
of (partially) elastic collision.


Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] vipbg
TAG      e-mail : pet### [at] tagpovrayorg

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