Draft program for view-dependent and time-dependent rendering
Improvments:
1. Add view-dependent effects
2. Add 'frame interval' variable
3. Now can switch between view-independent and view-dependent mode
4. Move the camera reading module to OpenGLShow funcion
Known Issues:
1. Defects at the edge of view-dependent and view-independent areas
2. Cannot reach the real-time speed in view-dependent mode