How to activate bodies from a step listener?

[hhyyrylainen]

I'm using a step listener to implement game object movement. I've been seeing a bug where when an object is initially touched by something else it can shoot off at high velocity. Just today I had the thought that that is probably caused by the bodies being asleep while accumulating velocity from repeated impulse applying. But I ran into a major issue: I apply the impulse with a step listener and I can't figure out how to activate the body without this assert triggering: JPH_ASSERT(body.IsInBroadPhase());

This is the code I tried:

physicsSystem->GetBodyInterfaceNoLock().ActivateBody(bodyId);

I've already been using the no-lock interface for setting the body velocity and angular velocity, which seems to work fine. But that above code causes an assert to trigger within like a second of things starting to happen.

I tried the locking variant but that just permanently locks up the entire process:

physicsSystem->GetBodyInterface().ActivateBody(bodyId);

Is there a correct way to activate bodies from a step listener that I missed?

[jrouwe]

The assert JPH_ASSERT(body.IsInBroadPhase()); means that you're trying to activate a body that hasn't been added to the PhysicsSystem (using BodyInterface::AddBody).

If you want a body to wake up when applying an impulse you need to call BodyInterface::AddImpulse instead of Body::AddImpulse. Otherwise you can indeed start accumulating velocity on a sleeping body (and if the body hasn't been added to the world it's the same thing). I'll have to add an assert there.

[hhyyrylainen]

Ah, turns out I have an underlying bug with bodies that are not in the broadphase being in the list of stuff to apply movement control to. I initially thought when I saw that assertion that I was doing something unexpected (as I had previously seen that same assert when I accidentally turned on multithreading for body adding to world despite using the basic single body add API). But now quickly testing adding a if (!body.IsInBroadPhase()) return; to my method, that stops the crashing when using that no lock interface. So yeah I think I did initially find the right API, I just had a bug elsewhere.

Thank you for the response. I'll investigate what's the root cause for bodies not being in the broadphase in my setup.

[hhyyrylainen]

Yeah that was exactly it, I had a bug in my code. There was a one frame window when part of my code thought that a body was already added to the world, but the code for adding the body to the world had not ran yet. I fixed that by skipping the physics body control code from running if the body wasn't actually added to the world yet.

So yeah, if anyone ever stumbles upon this discussion physicsSystem->GetBodyInterfaceNoLock().ActivateBody(bodyId); is the right API to use and it works perfectly fine as long as there isn't a bug elsewhere with body adding to the world happening too late.