[ODE] Collisions time steps & tunneling effect

[DjArcas]

If you're having a flat ground, the easiest way it to use a plane, which can
be thought of as an infinity big box, going down into the ground an
infinitely long way - so you can't get to 'the other side' of it.

Out of curiosity, how are you making your hovercraft float?

----- Original Message ----- 
From: "Flavien Brebion" <f.brebion@vrcontext.com>
To: <ode@q12.org>
Sent: Tuesday, July 22, 2003 10:26 AM
Subject: [ODE] Collisions time steps & tunneling effect


> Greetings,
>
> I'm using ODE 0.039 with OBB / tri-mesh collisions for
> an hovercraft racing game. I currently have some issues
> with collision detection.
>
> To simply describe the problem, small objets with high
> velocities suffer from the tunneling effect. Just using
> a flat ground made of 2 triangles, a pretty thick box
> just influenced by gravity, if falling from more than
> a few meters, passes through the ground more often than
> it does not. It seems pretty obvious why (ODE uses
> time steps, if the box is completely above the ground
> at the previous time step, and if it is completely below
> the ground at the next time step, no collision will be
> reported). It's less obvious how to fix it..
>
> The doc FAQ mentions the problem so i believe it's
> pretty common. It proposes:
>
> - to reduce the time steps: might work, but doing more
> time steps also reduces the performance since for the
> same elapsed time, you need to do N time steps instead
> of doing only 1. Also, in essence it doesn't fix the
> problem, just lessens it. A trick IMO.
>
> - increase ERP: don't think it helps if no intersections
> between the objects are reported, am i wrong ?
>
> - use a variable time step: how is that different than
> the first proposal ?
>
> So basically i'd like to know what everybody's thought
> are on this topic, and how you solved it (if you solved
> it!).
>
> Thank you,
>
> F. Brebion
>
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