This simulation demonstrates the collision detection between objects which are made of rigid bodies joined by 'link' constraints, like in this case where there are few chains made of balls linked by spherical joints. Chains will fall into the funnell and collide between themselves too.

Note that between the big spheres there are small spheres representing the joints: these small spheres does NOT perform collision detection, otherwise there would be interpenetrating objects. Meanwhile, the big spheres are colliding. Since rigid bodies are made of a big and a small sphere each, how is this possible? The trick: in order to exclude only some specific shapes from collision detection, inside a rigid body which has collide=ON, you can select that shape, then open its "Property window", go to the "Tags" tab and add an integer tag with name = "noc" (meaning 'NO Collision') and value=1.

(c) DeltaKnowledge 2007