The app I'm working on requires that we show the "horizon" associated with what an object (say a satellite) in space can see, based on its altitude and FOV. I typically can render this with no problem, except when the horizon circle contains the north pole, then all sorts of weirdness can happen. Here is an example:

On both the sceneview, the black outline correctly denotes what I expect to see, but the polygon doesn't fill correctly.
On the mapview, I expect to see something that looks like a sine wave filled in from the top.
In neither case did I get what I expected.
I've attached the code that generates this image. Run it and click the "Large Circle Issue" button.
Thanks,
David