Thanks, Keet! Updating the AMD graphics driver did indeed fix it. I should have tried that before posting.

Hi,

I'm sure this is just a newbie problem, but I did a search and couldn't find an answer - probably not using the right terms.

I've laid out a pretty simple floorplan, and defined the rooms. However, in the 3D view, there are black triangles coming from one corner of the floorplan (probably not ...