The Vector View-Up in Computer Graphics

In the existing textbooks on computer graphics, the vector view-up (VUP) is often used in lecturing the part of specifying the viewing coordinate system under the world coordinate system. However, the existing way of lecturing the vector VUP can not explain its actual function and exact physical meaning. The new conception of initial VUP is proposed and it is pointed out that the principle of rotating initial VUP around the vector n equals to the twist of the virtual camera. Further, for arbitrary vector VUP using initial VUP to allow it rotating twist angle around n axis, its solution method is given. Finally, the function glLookAt() of OpenGL is re-encapsulated. The scene rendering test on navigational simulator shows the proposed method is correct.