1. A concise explanation of the problem you're experiencing.
When I load world contries geojson in 3DView,cesium works well and smoothly.But when I changed to 2DView,it has low FPS.I cann't even wander!Can you tell how to solve the problem?
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.
My Cesium version is 1.5,OS is windows 7 and Chrome browser.