After Effects CS6 on Win 7 Pro. Trying to use the roto brush tool for the first time. I import my footage, double click it to get the roto layer, then click on the roto brush tool. Okay, I get the little green + to make my strokes, BUT the little green + is surrounded by a green circle, and whenever I try to make a stroke I get a fat green line that blocks me from seeing what I'm working on. Seems obvious that something isn't set right....but what? Any ideas? Thanks!