How to smooth polygon line

Is it possible to smooth polygon outline?

thanks

Are you talking about just the regular outlines like in this example?

If by smooth you mean you’re seeing antialias artifacts you want to get rid of, check out this thread about controlling the antialias in Cesium:

https://groups.google.com/d/msg/cesium-dev/XXXBFSYgb7s/FaBmLYhyCAAJ

For your first question, yes.

I have a polygon with many points, and I want the outline to be like in polyline.

You can use the built in outline as shown in that example. That uses the native WebGL lines I believe. If you’re trying to do something it can’t do (like do thicker lines), there’s been some discussion about using polylines for outlines to make them more versatile, which you can see in this GitHub issue:

It’s not currently being actively developed though so no timeline on when this feature would be added.