Cesium Visibility Analysis / Viewshed / ShadowMap / Line Of Sight

Hello,
I need viewshed structure in Cesium js.

I want to look at a certain angle from one point to another and color the places within the viewing distance. For example, if there is a mountain on the terrain, I want the front side of the mountain to be green and the back side to be red so that I cannot see the back side of the mountain.

Actually, my goal is to detect places where a signal emitter can transmit signals.
How can I set up this structure? Is there an example or can I do it using what//how?
It may be like in the picture

images

I would be very pleased if you could help.

Regards.