Box2D world locked

misterhup · May 2016

So I was playing with Box2D then I got this:

".\GiderosCodingEasy.lua:503: World is locked.
stack traceback:
	.\Box2dEasy.lua:497: in function 'update'
	main.lua:657: in function <main.lua:656>"

I get this when I try to update the world....more specifically when a collision occurs.. help?

dreiko65 · May 2016

Are you trying to remove the physics body on collision? If so you should probably set a timer that triggers when a collision occurs and removes the body when its complete.

totebo · May 2016

Yeah, you can't manipulate objects in Box2D from a collision handler. The solution is to wait a frame (until the next step) and then do it (like dreiko65 said).

misterhup · May 2016

All I actually want is to detect collision between 2 static box2d objects... So do I get this error because they are static?

hgy29 · May 2016

@misterhup,

As others said, you can't modify/update the world from within a collision callback, because technically the callback is already called from a world update. You have to defer your world changes until next frame.

Can your share the code that you use so that we can help you further ?

john26 · May 2016

I'm not sure if collisions exist between static objects. Static objects are not meant to move so it's hard to see how they would collide unless you create them directly on top of each other. If you want objects you move yourself, you should create kinematic objects. Finally if you want objects to move around according to forces like gravity, use dynamic objects.

So what are you trying to achieve with static objects?

misterhup · May 2016

@john26
They are static, Box2D speaking, but they move accordingly to some custom physics I made changing their position/rotation each frame. And when I mean colliding I basically mean touching (because I use Box2D just for its precision to detect collision between rotated objects)
I figured the problem out though. Thank you for all the help and support!

ar2rsawseen · May 2016

Just a note but static box2d bodies do not collide, you won't have an event,
Only dynamic collide with all types (dynamic, static, kinetic)

totebo · May 2016

I suppose static bodies can contain sensor fixtures which would trigger a collision.

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