Hello! Here's the deal. I have a long shot of a man (who needs to be cut out) approaching camera from a distance, so obviously he is very small at the beginning and large at the end of the shot. I've created a base frame at the point were he takes the whole frame to let Rotobrush remember his silhouette in full detail, and propagated backwards. Everything went ok and since the shot is long, I decided to create another base frame right before he becomes too small and propagated further back. And here's the issue. Since I haven't changed search radius, Rotobrush became all crazy picking up lots of background around the little man. I've tried lowering search radius value and it did work very well. But as you may have guessed, if I decrease search radius, Rotobrush propagates the whole shot again and that perfectly rotoed part were the man is big becomes messed up. So I think I need to keyframe search radius value, but this parameter has no stopwatch icon, so I guess it's impossible.
The only option I see here is to divide the shot into two layers, but while it could work it would be time consuming. Maybe you know of some workaround?