/// <summary>
/// This requires a world target point,
/// tuning parameters, and the time step.
/// </summary>
/// <param name="body">The body.</param>
/// <param name="worldAnchor">The target.</param>
public FixedMouseJoint( Body body, Vector2 worldAnchor ) : base( body )
{
jointType = JointType.FixedMouse;
frequency = 5.0f;
dampingRatio = 0.7f;
maxForce = 1000 * body.mass;
Debug.Assert( worldAnchor.isValid() );
_worldAnchor = worldAnchor;
localAnchorA = MathUtils.mulT( bodyA._xf, worldAnchor );
}