[ODE] Car Simulation(Lots of problems)

[Alen Ladavac]

Hey Jon,

Nice demo - I like the controls because they are very natural. It would be
nice to be able to
use mouse to look sideways while driving straight, but guess it's just my
subconscious PS paranoia... ;)

Have you noticed the wheels spinning in a strange way if you are trying to
get the car to a halt? If you press backwards for a moment while car is
moving slowly forward, you can get the wheels to spin backwards for a second
and then continue spinning forward. Do you know the reason for that?

Also, the car seems to rotate a bit too fast when moving very slowly. Are
you using some additional tweaks for rotation, besides normal steering?

Finally, which solver is that? :)

Alen




----- Original Message -----
From: "Jon Watte" <hplus-ode at mindcontrol.org>
To: "Robson Ito" <agemaniac at yahoo.com.br>; <ode at q12.org>
Sent: Wednesday, August 11, 2004 10:19
Subject: RE: [ODE] Car Simulation(Lots of problems)



The ODE documentation actually addresses some of these issues.

I don't use Bounce in the demo. However, when you slam into
some object, the integrator has to apply enough force so that
you both negate the velocity into the object, AND you move
the object out of the penetration in the next time step. This
means that you will get some non-zero velocity out of the
penetration even with zero bounce. You can reduce this effect
by reducing the global ERP, but that will make the entire
simulation much squishier. You can also reduce the effect by
making the time step smaller, because penetrations during a
single time step will be smaller.
There's no parameter named "bounce" so it's un-clear what you
are referring to -- Recoil? That's used when firing grenades.

I haven't paid that much attention to the wheels when pushing
into static objects -- I'd assume that they fix themselves as
soon as you stop pushing? If so, it's probably just the
inherent flex of the joint (controlled by ERP) making itself
visible. It could also be the fact that the wheels are actually
spheres, but are drawn as cylinders (so you catch on the side
a little bit).

I haven't seen the system explode; I've tweaked the damping
applied so that it seems stable to me. However, you can probably
add more damping if you want to avoid some explosion I haven't
seen.

Cheers,

/ h+


-----Original Message-----
From: ode-bounces at q12.org [mailto:ode-bounces at q12.org]On Behalf Of
Robson Ito
Sent: Tuesday, August 10, 2004 12:54 PM
To: ode at q12.org
Subject: RE: [ODE] Car Simulation(Lots of problems)


Hi..hey Jon Watte. it is a really good demo. i lost
some time playing with it. The explosions physic
effects is really good.
My problems with the car almost solved. Now it dont
fall so easy. I got just 2 strange things happening.
When i am in front of a wall and keep acelerating
against the wall the well seen to lose there Hinge2
axis sometimes. (does it have something to do with the
FudgeFactor??). I tried changing here and there, but
got nothing.
the other problem, more complex, is that, them the car
colide with a wall that is not a box, for example, if
it is a user mesh, sometimes the car is throw far
away, and sometimes the system seen to explode (very
rare).
Another newbie question: does the Bounce parameter
works? i tried to set it to 0 and nothing changed. the
car still bounce in the walls.

Any help would be great..thanks.





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