> The hopping is the correct solution of the model your are simulating.
> Of course this model is a really bad approximation of nature.
>
> These two states exist in your model but not in nature - there you have
> a deformation of the particles as well as the surface during collision -
> this involves all kind of dissipation of energy - friction and inner
> damping of the materials for example.  To model all these things
> precisely is extremely difficult but you can approximate them.  If the
> particle would actually be lying on the surface the simulation would be
> finished - there is neither kinetic nor potential energy in the system.
>
> What you say is essentially you want realism without much computation -
> this is hardly possible.

I think you've misunderstood what I'm saying. With "lying on the floor" I
didn't mean "lying there totally still". Maybe its sliding along the x-axis.

The basic idea is simple: a particle bounces around most of the time, that's
essentially why particle system are written in the first place. Now, when
you just keep with bouncing particles all the time, you get what I'm
getting: a particle will eventually oscillate on a surface, cause though it
does lose some energy everytime it hits the floor, it's always a percentage
of the energy it had before impact, thus, there'll always be an energy
residue. Now, in an Euler System, energy due to gravity gets added in steps,
as do several other calculations. Even when a particle lies motionless on a
surface, gravity will pull it down, adding energy (which is always stored as
a velocity vector) which will lead it to oscillate on the surface, even
though it visibly doesn't move a bit (unless with a microscope).

Now, what I want to do is to simplify the model when the particle starts to
oscillate: instead of oscillating, I slide the particle along the surface -
if possible. If a particle lies on the y-plane and its just y-velocity from
gravitation, there's no movement at all. But when there is some x-velocity,
it will slide along the x-axis. Friction and dampening is left out for
simplicities sake, its a particle system and, IMHO, doesn't need physical
calculations like friction and dampening to slowly stop a particle from
sliding along a surface.
Now, with those assumptions for my particle system, I want a very simple
approach to calculate how much slower a particle would get when moving
uphill, that's all I was asking for. I've stated that I don't need friction,
dampening etc. And we're still discussing just that: friction, dampening,
the model I'm using...

Don't get me wrong, the suggestions and comments do have valid points. But
I'm just not after a system which calculates hundreds of tiny *balls* with
incredible physical accuracy. A particle system, in most cases, is used and
designed to quickly and efficiently create hundreds or thousands of tiny
objects which together give the *impression* of a more complex simulation.
Instead of simulating actual millions of dust particles for smoke, one uses
a few hundred and attaches some media-spheres to a particle, so that, in the
end, it *looks* like real smoke.

The hopping particles *look* correct, I'm not bothered about that. I'm
bothered by the parsing time and thus want something even more simple which
may spare the CPU of such intensive processing, as long as the end result
stills *looks* correct.

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

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