[ODE] more physics

[Tony Peguero]

>Costs in what way? It does say memory usage and how much of
>the cpu per frame the physics system takes. What other costs
>are there?

He he. You must have been working with open source projects for quite a
while to have forgotten that some things cost money. Some physics engines
cost a LOT of money.

>Also is it just me or do the chain and hinge behave strangly?
>If you continue to force it upwards it starts to wobble. Like
>a snake or something. Maybe it's just me and thats how it
>should behave.

I noticed that too. I think it's because of the way the keyboard controls
were written, rather than a problem with the engine. When you press the lift
key, it applies a momentary impulse to the end of the chain. When you hold
the button down it applies repeated impulses, not a constant force, so the
end of the chain is basically being shaken up and down.


-----Original Message-----
From: ode-admin@q12.org [mailto:ode-admin@q12.org]On Behalf Of Joakim
Eriksson
Sent: Friday, 1 November 2002 10:27 a.m.
To: ode@q12.org
Subject: SV: [ODE] more physics


> > looks like another physics engine...
> >
> > www.tokamakphysics.com
>
> interesting. yet another mention of iterative constraint
> solving methods here. the demos are kind of bare bones
>(i.e., like ODE's bare bones demos). no mention of the cost.

Costs in what way? It does say memory usage and how much of
the cpu per frame the physics system takes. What other costs
are there?

> the box stack demo has an interesting flaw: a nudged stack
> will tip over, then freeze part of the way down. this suggests
> that 'stable'  box stacking is achieved through simply turning
>off the phisics for a  stationary stack

Yes, seems like the objects sleep VERY quickly. After just a few
tries I manage to get it to sleep in a physicly impossible position.
(If the simulation had run for just a few ticks more the boxes
would have fallen over) but they quickly froze in place.

> the collision looks like it allows penetration, like ODE. if
> you collapse the chain on top of itself it will squish into
> itself a bit then expand out.

It does indeed allow penetration. Just move closer to a object
and spawn a sphere or something. You can see that even if the
object is inside another object he can handle it.
Its also a dead give away that he for the moment only handles
primitives vs primitives and primitives vs static triangle meshes.

It seems to be able to handle quite a lot. It does use a bit of
memory 500Kb in some cases but they do contain quite a lot of
objects. Too bad they dont have any more information on thier
method.

Also is it just me or do the chain and hinge behave strangly?
If you continue to force it upwards it starts to wobble. Like
a snake or something. Maybe it's just me and thats how it
should behave.

/Joakim E. - www.planestate.net
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