private void removeObstacle(short index) {
		if (obstacleIndexAndFace != null) {
			obstacleIndexAndFace[0] = obstacleIndexAndFace[1] = -1;
		}
		if (index < 0 || index >= model.getObstacleCount())
			return;
		model.removeObstacle(index);
		viewer.removeObstacle(index);
	}