View Full Version : Rigid Body Ghost

05 May 2008, 06:30 AM
Hi everybody,

Im creating a scene where i have 2 balls thrown across the ground. They are both rigid bodies that bounce along the floor until they come to rest.

All is working fine, But i don't want the balls to collide with each other.

You can think of it as a saved ghost from a racing game.

Unfortunately I am unable to do this in post production, it needs to be done in real-time (or close too)

Thanks for the help !!


05 May 2008, 04:52 PM

I am not sure I completely understand what you are trying to accomplish so my solution might not be suitable.

If you are trying to obtain rigid body behavior but yet, want the active rigid bodies to ignore each other, I would use the rigid body layer collision attribute.


1. Create two spheres, raise them some, make them active rigid bodies, attach gravity to them.
2. Create an object that you want the spheres to collide with. Some sort of ground, cube, whatever.
3. DUPLICATE your ground object.
4. Make both ground objects passive rigid bodies.
5. Set one of your spheres to be on layer 1, and also set one of your passive rigid bodies on layer 1 (The name of the attribute in the rigid body is actually "collision Layer", just change it to 1 for 1 active and 1 passive rigid body).

Again... I am not sure this helps. Let me know if it does.

05 May 2008, 06:44 PM
I think collision layer 0 will automatically collide with everything, so each ball could be collision layer 1,2 and the ground could be collision layer 0 and it will work (no need for duplicate grounds).


05 May 2008, 09:52 PM
hey untelon,

Collision layers are exactly what i was after, it works as i'd hoped.

ranxx, I tried leaving the ground on collision layer 0, but the balls just pass through.
Is there another setting to make it collide with all layers?

Thanks for the help!


05 May 2008, 09:56 PM
Hey ranxx,

just found out its actually collision layer -1 (minus one) that collides with all objects.

Thanks again !

05 May 2008, 09:57 PM
its actually -1 for collide with all on the collision layers


05 May 2008, 10:53 PM
whoops, my bad, thanks todd.


its actually -1 for collide with all on the collision layers


05 May 2008, 12:27 AM
not a problem.
there are a bunch of other hacks for allowing intersection on collision layers and a few otehr helpful techniques that I should post sometime

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05 May 2008, 12:27 AM
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