=head1 NAME
Box2D::b2GearJoint - Connects two joints together.
=head1 SYNOPSIS
my $joint = $world->CreateJoint( $joint_def );
$joint->SetRatio( $ratio );
=head1 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).
=head1 METHODS
=head2 GetAnchorA()
Get the anchor point on bodyA in world coordinates. Implements
C<Box2D::b2Joint>.
Returns a C<Box2D::b2Vec2>
=head2 GetAnchorB()
Get the anchor point on bodyB in world coordinates. Implements
C<Box2D::b2Joint>.
Returns a C<Box2D::b2Vec2>
=head2 GetRatio()
Returns a C<float32>
=head2 GetReactionForce( $inv_dt )
Get the reaction force on body2 at the joint anchor in Newtons.
Implements C<Box2D::b2Joint>.
Parameters:
=over 4
=item * C<float32> C<$inv_dt>
=back
Returns a C<Box2D::b2Vec2>
=head2 GetReactionTorque( $inv_dt )
Get the reaction torque on body2 in N*m. Implements C<Box2D::b2Joint>.
Parameters:
=over 4
=item * C<float32> C<$inv_dt>
=back
Returns a C<float32>
=head2 SetRatio( $ratio )
Set/Get the gear ratio.
Parameters:
=over 4
=item * C<float32> C<$ratio>
=back
=head1 SEE ALSO
=over 4
=item * L<Box2D>
=item * L<Box2D::b2GearJointDef>
=item * L<Box2D::b2Joint>
=item * L<Box2D::b2World>
=back
=head1 BUGS
See L<Box2D/BUGS>
=head1 AUTHORS
See L<Box2D/AUTHORS>
=head1 COPYRIGHT & LICENSE
See L<Box2D/"COPYRIGHT & LICENSE">
=cut