how to analyse the visibility from some point to another point(with 3dTile model)

1. A concise explanation of the problem you're experiencing.

2. A minimal code example. If you've found a bug, this helps us reproduce and repair it.

3. Context. Why do you need to do this? We might know a better way to accomplish your goal.

4. The Cesium version you're using, your operating system and browser.

Do you mean like described in this thread?

https://groups.google.com/d/msg/cesium-dev/DxSyhcyM2mQ/UNgA4uhxAAAJ

If so, see the answer there as well!