1. A concise explanation of the problem you're experiencing.
I published an Arcgis Map Server and then i loaded it in my Cesium project, it worked.
but i splice the layer into 11 pieces, how could i pick them by mouse over?
i used 'sceneMode:Cesium.SceneMode.SCENE2D',
3. Context. Why do you need to do this? We might know a better way to accomplish your goal.
To pick imagery layer's feature my mouse click, get the id and geometry infomation
4. The Cesium version you're using, your operating system and browser.
Cesium1.50/windows10/Chrome
I see “view in ArcGIS javascript” links in the link you have but not the Cesium viewer. Do you have a direct link to the Cesium one? It would also help to share a code snippet of how you’re adding it in CesiumJS.
If you’re using ArcGisMapServerImageryProvider you should be able to use the pickFeatures function on mouse click: