Allow loading terrain and imagery data only inside a defined area

Hello everyone,

I need your help to resolve 2 tasks:

  1. I want to allow loading of terrain and imagery data at only specify GPS boundary area instead of depending on camera position and zoom level. How can I achieve this?

  2. Also, how can I allow loading terrain and imagery at specific Level Of Detail, for example LOD=11 inside this specified boundary, and maintain this scene regardless of camera and zoom level?

If you know how should I modify cesium source code to achieve this, please let me know. Thanks alot!