Vision of camera to object (model, billboard, etc)

CesiumJS
1

is there any method that tells whether an object is up the vision of the camera?

2

The low-level code in Cesium uses CullingVolume.computeVisibility to test if a sphere is in view like done here:

https://github.com/AnalyticalGraphicsInc/cesium/blob/master/Source/Scene/Scene.js#L932

Patrick