1. A concise explanation of the problem you're experiencing.
I'm seeing extraneous visual artifacts when drawing a polygon in the sandcastle.
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.
I want to draw using the technique shown in the sandcastle without extraneous rendering artifacts.
4. The Cesium version you're using, your operating system and browser.
Cesium 1.48
Windows 10
Chrome