OpenGL绘制桌子和茶壶，添加键盘对茶壶的控制,主要是茶壶沿着桌面的平移操作和茶壶绕自身轴的旋转操作 实现透视投影和正投影之间的转换，使用键盘移动观察相机-OpenGL drawing table and teapot, add keyboard control of the teapot, mainly along the teapot and tea desktop panning rotation around its own axis operation　to achieve perspective and orthographic projection conversion between the observed use the keyboard to move the camera