Specifying 3D View
•Center of camera (x, y, z)   : View Reference Point (VRP) • Direction of pointing (q,j) : View Plane Normal (VPN)
• Camera tilt (w)                   : View Up (VUP)
• Area of film (w, h)             : Aspect Ratio (w/h),
•                                                   Field of view (fov)
• Focus (f)                             : Will consider later