I've been playing with Sketchup a bit and I have something that is really bothering me. How do you get rid of the big, ugly, black spots on the corners/intersect points of the blocks? They disappear automatically for a few seconds while I'm moving blocks around, but they reappear as soon as I place the blocks and show up in my exported screenshots. I've gone through the tutorials, program manual, and the online help and can't seem to find how to do it so that my models look clean and sharp like the ones posted here..