Maybe some more technical information is required, so instead of answering
all of you helpful guys one by one, I'll have another shot:

My particle system doesn't use rotational energies, the particles don't
interact, they're actually points and thus don't roll but rather slide,
though without friction or dampening. What happens though is when a particle
hits a wall, the velocity in the direction of the surface-normal gets
reduced somewhat, in effect, a ball dropping to the floor won't jump as high
as it was dropped from. But when it's flung, it will still retain the
velocity in the x-direction.

Now, from there on, a particle moving uphill would bounce hundreds of times
up the slope, whereby it loses it's velocity that is moving it upward in the
first place: thus, it slows down, comes to a halt, and moves back down: in
the test-animations everything is looking a-okay..
But instead of calculating thousands of bounces, I want to have a quick
formula to move the particle somewhat uphill, take some proper amount of
velocity, and save thousands of bounces, thus saving precious parsing time.

While at work and keeping pondering about this, I thought that maybe it'd be
possible to calculate the speed the particle would get when free-falling,
that velocity is somehow calculated along with the dot-product of the
downward/gravity times the slope-surface-normal. Add/subtract that to the
particle and it will slow down, stop, and turn back at some point.

Now, precision-wise the particle would be doing some physics-ignorant stuff:
when its rolling uphills, it already loses some speed, and thus wouldn't get
that far as it would when just moving it uphill and subtracting some speed
then. But, due to the small timesteps the system uses, I think I can just
forget about that, it shouldn't be noticeable. Doing a 100% correct
physical-particle System wasn't my goal. :-)

Still, all your comments and suggestions are good food for thought, and I'll
have some thinking time about it tomorrow, when I'm fully awake again.
Thanks all!

Regards,
Tim

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

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