A bug in Silverlight 1.1 Alpha Polygon Visual?

I’m working on my 3D engine still and all of a sudden all my polygons didn’t show up on the screen.
After some hours of debugging I figured out what the problem was. At one point yesterday I removed some casts I had for setting the points for the polygons. The Point class in Silverlight has X and Y as double but the rendering engine does not seem to manage this at all. I have to cast it to int before I use them and remove all decimals.

This clearly can’t be “by design”.