B2.GearJoint

Supported platforms:
Available since: Gideros 2011.6
Inherits from: b2.Joint

Description

A gear joint is used to connect two joints together. Either joint can be a revolute or prismatic joint. You specify a gear ratio to bind the motions together: coordinate1 ratio * coordinate2 = constant The ratio can be negative or positive. If one joint is a revolute joint and the other joint is a prismatic joint, then the ratio will have units of length or units of 1/length.

Examples

Gear joint combining revolute and prismatic joints

--create empty box2d body for joint
local ground = world:createBody({})

--create revolute joint
--note that ground should be passed as first parameter here
local jointDef = b2.createRevoluteJointDef(ground, body1, 300, 300)
local revoluteJoint = world:createJoint(jointDef)
--set motor
revoluteJoint:setMaxMotorTorque(1)
revoluteJoint:enableMotor(true)

--axisx, axisy values usually between 0 and 1
--note that ground should be passed as first parameter here
local jointDef = b2.createPrismaticJointDef(ground, body2, 350, 100, 0.3, 1)
local prismaticJoint = world:createJoint(jointDef)
--set motor
prismaticJoint:setMaxMotorForce(1)
prismaticJoint:enableMotor(true)

--create gear joint using two already created joints
local jointDef = b2.createGearJointDef(body1, body2, revoluteJoint, prismaticJoint, 1)
local gearJoint = world:createJoint(jointDef)

Methods b2.GearJoint:getRatio returns the gear ratio b2.GearJoint:setRatio sets the gear ratio

Events Constants

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• B2.Joint
• LiquidFun