On the one hand . creating virtual scene of complicated traffic facility ( for example crossroads ) by using opengl has become very difficult . the research and application of driving simulator has been furthered and extended and the virtual scene models come to more complex 但是，一方面，由于驾驶模拟器的研究领域和应用范围的扩展，构造的虚拟场景的复杂度加大，使用opengl从底层构造像立交桥这样复杂的交通设施的虚拟场景，已经显得力不从心了。
