B2.World

From GiderosMobile

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Supported platforms: Platform android.pngPlatform ios.pngPlatform mac.pngPlatform pc.pngPlatform html5.pngPlatform winrt.pngPlatform win32.png
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