[ODE] Question about variable step size and collision detection

Daniel K. O. danielko.listas at gmail.com
Sun Dec 17 20:21:48 MST 2006

Per Bull Holmen escreveu:
> of camera angles etc. This means that when colliding
> objects penetrate each others, it will be all too
> visible - 2D graphics must be pixel perfect.
I think you are exagerating a bit here. :)
Other than Tetris, "pixel perfect" response is unnecessary. Actually, I 
would dare to say it's wrong, you usually work on everything 
independently of pixels.

> 1) Bullet physics engine, which has very sophisticated
> collision detection, can according to their developer
> be used together with ODE's dynamics. This sounds like
> a great solution, but I have a feeling it still won't
> let me avoid object penetration during impact. Any
> experience or knowledge about using the two together
> is welcome.
Maybe your audience are super heroes who can detect "hey that bullet 
killed the enemy only when it entered 3 pixels inside the enemy". :P

Unless you plan to make the bullets reflect on something, like a pool 
game (and even on a bullet-pool game ODE would be OK), you won't care 
for penetration. Bullets are expected to fly fast, you can't show them 
in every single position, nor expect the user to see where was the exact 
contact point. The only worry is to make sure you don't miss any 
collision; you do that by "attatching" a capsule/ray to the bullet, long 
enough so it will sweep the trajectory without missing anything.

Why don't you show us a more specific scenario you think ODE may cause 
problems? Then we can suggest more specific solutions.

> Id like to avoid the very-small-timestep approach
> because it would be inefficient, and though it might
> work on my rather new IntelMac, it might not work on
> older machines.
Just wondering, how many objects would you be simulating? More than 100? 
500? 1000? All of them generating collisions like gas atoms moving 
inside a closed box?

Daniel K. O.

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