B2.World

Supported platforms:
Available since: Gideros 2011.6
Inherits from: EventDispatcher

Description

The b2.World class inherits from the following class: EventDispatcher.

The b2.World class manages all physics entities and dynamic simulation. It is possible to create and manage more than one b2.World instance.

Examples

Creating Box2d body and moving Bitmap along the body

require "box2d"
local world = b2.World.new(0, 10, true)

--create ball bitmap object from ball graphic
local ball = Bitmap.new(Texture.new("ball.png"))
--reference center of the ball for positioning
ball:setAnchorPoint(0.5,0.5)
 
ball:setPosition(100,100)
 
--get radius
local radius = ball:getWidth()/2
 
--create box2d physical object
local body = world:createBody{type = b2.DYNAMIC_BODY}
local circle = b2.CircleShape.new(0, 0, radius)
local fixture = body:createFixture{shape = circle, density = 1.0, 
friction = 0.1, restitution = 0.2}
ball.body = body
 
--add to scene
stage:addChild(ball)

stage:addEventListener(Event.ENTER_FRAME, function()
	-- edit the step values if required. These are good defaults!
    world:step(1/60, 8, 3)
	ball:setPosition(ball.body:getPosition())
	ball:setRotation(math.rad(ball.body:getAngle()))
end)

Detecting collisions between bodies

--add collision event listener
world:addEventListener(Event.BEGIN_CONTACT, function(e)
    --getting contact bodies
    local fixtureA = e.fixtureA
    local fixtureB = e.fixtureB
    local bodyA = fixtureA:getBody()
    local bodyB = fixtureB:getBody()
     
    --do what you need with colliding bodies
end)

--add collision event listener
world:addEventListener(Event.END_CONTACT, function(e)
    --getting contact bodies
    local fixtureA = e.fixtureA
    local fixtureB = e.fixtureB
    local bodyA = fixtureA:getBody()
    local bodyB = fixtureB:getBody()
     
    --do what you need with colliding bodies
end)

--add collision event listener
world:addEventListener(Event.PRE_SOLVE, function(e)
    --getting contact bodies
    local fixtureA = e.fixtureA
    local fixtureB = e.fixtureB
    local bodyA = fixtureA:getBody()
    local bodyB = fixtureB:getBody()
     
    --do what you need with colliding bodies
end)

--add collision event listener
world:addEventListener(Event.POST_SOLVE, function(e)
    --getting contact bodies
    local fixtureA = e.fixtureA
    local fixtureB = e.fixtureB
    local bodyA = fixtureA:getBody()
    local bodyB = fixtureB:getBody()
     
    --do what you need with colliding bodies
	
	--additionally get collision force
	print(event.maxImpulse)
end)

Methods b2.World.new b2.World:clearForces call this after you are done with time steps to clear the forces b2.World:createBody creates a rigid body given a definition b2.World:createJoint creates a joint given a definition b2.World:createParticleSystem create particle system b2.World:destroyBody destroys a rigid body b2.World:destroyJoint destroys a joint b2.World:getGravity returns the gravity vector b2.World:queryAABB query the world for all fixtures that potentially overlap the provided AABB b2.World:rayCast raycast the world for all fixtures in the path of the ray b2.World:setDebugDraw registers a b2.DebugDraw instance for debug drawing b2.World:setGravity sets the gravity vector b2.World:step takes a time step

Events Event.BEGIN_CONTACT Event.BEGIN_CONTACT_PARTICLE Event.END_CONTACT Event.POST_SOLVE Event.PRE_SOLVE Constants