initialize method
Initialize the bodies, anchors, and reference angle using the world anchor.
Implementation
void initialize(A body1, B body2, Vector2 anchor) {
bodyA = body1;
bodyB = body2;
localAnchorA.setFrom(bodyA.localPoint(anchor));
localAnchorB.setFrom(bodyB.localPoint(anchor));
referenceAngle = bodyB.angle - bodyA.angle;
}