GroundPrimitive Polygon visual artifacts at pole

[shunter]

Sandcastle example

This is a single polygon at the pole. There are multiple visual artifacts:

[ggetz]

I did some debugging here, and this artifact happens only with ground polygons. As a workaround, you can set height: 0 to use a regular polygon.

This is caused by using spherical texture coordinates for ground primitives, particularly a discard that that clips any values computed outside of the [0, 1] range for UV coordinates.