Strange behaviour when combining CollisionListeners with .addToIgnoreList about libbulletjme HOT 4 CLOSED

Thanks for bringing this to my attention.

Like many physics engines, Bullet includes performance optimizations that cache contacts from one time step to the next. While I haven't stepped through the code, I suspect that's what happened in your example. Perhaps there is a mechanism to clear cached contacts, or if not perhaps I can add one. But maybe the callback happens too late to avoid contact forces. I'll investigate further.

As for detecting the collision earlier, Bullet includes a mechanism to report axis-aligned bounding-box (AABB) overlaps during broadphase. Not all AABB overlaps turn into actual collisions, but I'm pretty sure every collision is preceded by an overlap. Said mechanism can be used to disable collisions dynamically. The mechanism isn't quite exposed in Libbulletjme. All that would be needed would be to make the notifyCollisionGroupListeners_native() method public or add a listener mechanism to it. I suspect that's the best solution to your (hypothetical?) problem. Look for something in the next release...

from libbulletjme.

@JBraig I added a simple mechanism to disable collisions between particular objects on the fly. Please take a look and tell me whether you think the mechanism will meet your needs: f7cfb87

from libbulletjme.

That should be a sufficient solution for my needs, thanks a bunch!

from libbulletjme.

That should be a sufficient solution for my needs, thanks a bunch!

Glad to hear it! The "simple mechanism" of needsCollision() will be included in the v12.8.0 release, which should be published to MavenCentral later today.

But maybe the callback happens too late to avoid contact forces. I'll investigate further.

I investigated this question. For the record, the callback is invoked during space.distributeEvents(), not during space.update(). That's definitely too late to avoid contact forces. I'm working on an interface to obtain collision events sooner, equivalent to gContactStartedCallback and gContactProcessedCallback in Bullet. It's partially implemented in v12.8.0 .

from libbulletjme.