collision rules

[dannisliang]

Setting collision rules when two objects collide does not seem to be immediately effective

[RossNordby]

The collision rule for a pair is calculated by the broad phase upon pair overlap detection. Modifications to the collision rules of objects after that point won't be seen until the next frame, if I remember correctly.

(Incidentally, this is part of the reason why bepuphysics2 doesn't have 'collision rules', just callbacks that return true/false for creating a pair or creating a constraint that the user defines however they want.)

[dannisliang]

How to modify it? implement an immediate rule change ，thank you

[RossNordby]

It's been years and years since I messed with this, so I don't remember all the details- turns out there is actually an event handler (see the collisionRulesUpdatedDelegate on BroadPhaseEntry) through which the pair overlaps get updated when collision rules on collidable are modified, and that should affect any already-created pairs, which should in turn inform contact constraints later that frame.

Is it possible that you're using a deferred event handler that runs after the timestep ends, rather than an immediate event handler?