修改示例程序的gluLookAt()函数，把它改为模型变换函数glTranslatef(),并使用参数（0.0,0.0，-5.0）。这个函数的效果应该和使用gluLookAt()函数的效果完全相同。为什么这两个命令的效果会完全相同呢？-Modify the example program gluLookAt () function, changed it to model transformation function glTranslatef (), and use the parameters (0.0, 0.0, 0.0). This function should be used and the effect of gluLookAt () function of exactly the same effect. Why the effect of the two commands will be exactly the same?