Polygon - depthFailMaterial

[TrainedTrex]

Feature

depthFailMaterial for Polygons

Request: Implement depthFailMaterial for Polygons

The goal is for there to be an easier way to draw/color/highlight arbitrary surfaces on 3D Tiles, regardless if they are vertical or horizonal surfaces.

Community forum request

This request applies more to vertical surfaces, as you see the expected behavior when you drape polygons that are clamped to ground over terrain/3D tiles as long as they are approximately tangential to the WGS84 ellipsoid. Similar issue as seen in the Polylines implementation

@ggetz for vis