使用OpenGL画七条曲线：Bezier曲线；3阶（2次）均匀B样条曲线；3阶（2次）准均匀B样条曲线；3阶（2次）分段B样条曲线；4阶（3次）均匀B样条曲线；4阶（3次）准均匀B样条曲线；4阶（3次）分段B样条曲线-Use OpenGL drawing seven curves: Bezier curves　3rd order (2) uniform B-spline curves　3rd order (2) quasi-uniform B-spline curves　3 step (2) above B-spline curves　4 bands ( 3) uniform B-spline curves　4 bands (3) quasi-uniform B-spline curves　4 bands (3) B-spline curve segments