[ODE] contact joints / attaching them

[Flavien Brebion]

If a ball is on one side of a wall at the start of a timestep,
and on the other side at the next timestep, no collisions will
be reported, and the ball will pass through it. That's what
i call the "tunneling" effect, as opposed to "sweep collisions".
And that's why i need different timesteps.

Sweep collisions have been discussed to death on this list
before, and from what i remember the conclusion was that ODE
was unable to do it at the moment. Tunneling is generally not
a problem when you have big objects that move slowly; but
occasionnally, if you get a smaller object that moves pretty
fast, it will show up. That's what i'm trying to fix. Hell,
even the samples suffer from it :) Replace the ground by a
pretty thin box, drop a cube on it, repeat and rince, and
observe..

F. Brebion


-----Original Message-----
From: ode-bounces at q12.org [mailto:ode-bounces at q12.org]On Behalf Of Steve
Baker
Sent: samedi 11 octobre 2003 03:20
To: Flavien Brebion
Cc: Dino Patti; ode
Subject: Re: [ODE] contact joints / attaching them


Flavien Brebion wrote:
> I don't see why. The collision detection functions are completely
> independant of the timestep. Notice that the time step parameter
> isn't even involved in collisions

It isn't?   How can the system tell whether a ball thrown at a
wall - which is on one side of the wall at the start of the timestep
  - and on the other side at the end of the timestep?

If the ball is in one 'world' and the wall is MOVING and in another
world - then having variable timesteps becomes a nightmare.

Also, the force of the ball hitting the wall affects both the
ball AND the wall - so if they are in different timestep worlds,
life would probably get VERY complicated.

---------------------------- Steve Baker -------------------------
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