> That is to be expected - you diminish the velocity during every
> collision but none the less the particles will still hop on the surface.
>   - the hops will get smaller over the time but this won't help of
> course.   This hopping is in fact the correct solution for your
> simulation problem.

The hopping isn't the correct solution, an object doesn't hop on the surface
of something forever (maybe on an electrostatical level, but that's not what
I'm after).

> What you need is a more realistic model of the
> surface contact - you model the collision by inverting the particle
> velocity but you would need to model the damping during the longer time
> of actual surface contact.  This of course will not really solve your
> performance problem in the end because you will need small time steps
> during the collision but it will improve the quality of the simulation -
> in the end your particles will smoothly 'flow' on the surface.

Why would I want damping? There are two possible states: a particle is
air-born, or its lying on a  surface. When lying on a surface, normally
friction, inertia and whatnot would affect the particle. Now, leaving
friction out of the equation, all I need is to find the velocity the
particle loses when rolling uphill. And I want to achieve that without
thousands of trace-calls to the surface.
What I'm reading out of your suggestion is to use actual dampening instead
of losing velocity due to impact, but keep on going with the
parsing-intensive small timesteps. I wouldn't win anything that way,
particles move properly as it is, using a different algorithm with roughly
the same complexity doesn't avoid long parsing-times.

-- 
"Tim Nikias v2.0"
Homepage: <http://www.nolights.de>
Email: tim.nikias (@) nolights.de

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