public RigidBody getRigidBody(TransformGroup transformGroup) {
		for (Iterator<RigidBodyContainer> it = rigidBodies.iterator(); it
				.hasNext();) {
			RigidBodyContainer container = (RigidBodyContainer) it.next();
			if (container.transformGroup == transformGroup) {
				return container.rigidBody;
			} else if (container.alternateTransformGroup == transformGroup) {
				return container.rigidBody;
			}
		}
		return null;
	}