Attach particles to surface of physX simmed geo?

[mitchfx]

Siblings are not merely particles born in the same event, but particles with the same *parent* particle (like real life sibling relationships in a family). So for example, if you had a spawn operator creating new particles by travel distance, all those spawned particles would be siblings with each other, and their parent would be the particle that spawned them.

Note: the Birth Surface operator creates implicit parents for all particles born on a particular surface, so that they are enforced as siblings. This way, all particles born on a spline, for example, would be siblings with each other even though there's no actual parent particle in the sim.

So the sibling relationship would come in handy in the PhysX Bind settings if you wanted to bind particles spawned on a spline together, into a rope for example.

Ok, this makes sense.  Let me ask you this...are particles born from different Birth Shape operators in unique events (but in the same flow) considered non-siblings?  Quite often I have a set of particles created in one Birth Shape that I want to bind to particles created in another Birth Shape from a different object, but not have them bind to each other.  However whenever I check the bind non-siblings option in PhysX Bind nothing binds at all.  Is this normal? 

Thanks again.