Jeffrey T. Palmer > Box2D-0.07 > Box2D::b2GearJoint

# NAME

Box2D::b2GearJoint - Connects two joints together.

# SYNOPSIS

my \$joint = \$world->CreateJoint( \$joint_def );
\$joint->SetRatio( \$ratio );

# 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.

Warning: The revolute and prismatic joints must be attached to fixed bodies (which must be body1 on those joints).

# METHODS

## GetAnchorA()

Get the anchor point on bodyA in world coordinates. Implements Box2D::b2Joint.

Returns a Box2D::b2Vec2

## GetAnchorB()

Get the anchor point on bodyB in world coordinates. Implements Box2D::b2Joint.

Returns a Box2D::b2Vec2

## GetRatio()

Returns a float32

## GetReactionForce( \$inv_dt )

Get the reaction force on body2 at the joint anchor in Newtons. Implements Box2D::b2Joint.

Parameters:

• float32 \$inv_dt

Returns a Box2D::b2Vec2

## GetReactionTorque( \$inv_dt )

Get the reaction torque on body2 in N*m. Implements Box2D::b2Joint.

Parameters:

• float32 \$inv_dt

Returns a float32

## SetRatio( \$ratio )

Set/Get the gear ratio.

Parameters:

• float32 \$ratio