PolygonGeometry not receiving shadows

1. A concise explanation of the problem you’re experiencing.

Polygons appear not to receive any shadows despite being enabled for it.

2. A minimal code example. If you’ve found a bug, this helps us reproduce and repair it.

A modified sandcastle example https://goo.gl/c1oFMt

3. Context. Why do you need to do this? We might know a better way to accomplish your goal.

Thanks for the Sandcastle example Xavier! I think it is a bug, and I’ve reported it here: