是实现一个漫游功能，当按下left键后向左转，right向右转，up前进，down后退，page up向上仰。g_Angle,rad_xz的初始值均为0。g_eye[0],g_eye[1],g_eye[2],分别代表眼睛的x,y,z g_look是参考点-Is to implement a roaming, when you press the left button, left turn, right turn to the right, up forward, down back page