[ODE] purpose of joint groups?

[Roel van Dijk]

Well, one use is with the contact joints. Every simulation step you create 
contact joints. These joints are placed in a joint group. After stepping the 
world you need to get rid of these contacts, otherwise objects will kinda 
stick to each other after a collision. You do this be making the contact 
joint group empty.
I don't know if they have any special purpose. I guess you can get the same 
functionality form a linked list.

Roel van Dijk

> Can someone explain what's the purpose of joint groups? when should they be
> used?
> I can't find that in ODE manual.