Collisions between 2 worlds

jeromegsq

Hello,

This is the first tile i use box2D and i want to know if it is possible to detect collisions between 2 objects which they are not in the same world ?
If it is not possible, i want to make something like Flappy Bird were an object fall and other object like all sleep to the left of the screen. How can i do ?

Thank you

jdbc

Box2d uses global coordinates, so your player body could be always in the middle of the screen with constant X coordinate (320 for example if you use 320x480 screen resolution) and move the other object from right to left or left to right depending the sense of scrolling.

I do not understand what you mean with 2 objects not in the same world. May be multiverse?

jeromegsq

Something like that :

self.world1 = b2.World.new(0, 25, true)
self.world2 = b2.World.new(-25, 0, true)

The world1 make the object fall
body = self.world1:createBody{type = b2.DYNAMIC_BODY}

The world2 make the wall going to the left
body2 = self.world2:createBody{type = b2.DYNAMIC_BODY}

They can't interact because they are not in the same world

jdbc

Two different physic worlds in the same game? Just a multiverse theory :-)

totebo

@jeromegsq, I think I know what you mean, but in Box2D there is (generally speaking) really no need for more than one world.

If you want a body to drop and a wall to move left, then you can simply create a dynamic body (which will drop because it's dynamic) and create a kinetic body for the wall (which will move only when you tell it to) and set its LinearVelocity to (-1, 0). The dynamic body will drop and the kinetic body will move left. They will collide, and both live in the same world.

jeromegsq

Ok it works thank a lot !

totebo

Great! Look forward to seeing the falling bodies and moving walls in a game.

jeromegsq

Yes this is for a company, but i have done another app :

https://play.google.com/store/apps/details?id=com.dragonflyapps.savethedigger
https://play.google.com/store/apps/details?id=com.dragonflyapps.whackazombie