Well, but whole scene is filled with objects. The plane in the backgroud fills it so there’s no any gap. I tried to render in max the image itself with alpha and also the velocity map with alpha, no difference.
When I set a movement to this plane, strange thing occurs – inside the ball there is the proper ball MB, and outside there’s the lost blur of the ball, but it goes in a wrong direction. Not in the direction of the ball movement, but in the direction of plane movement (plane = object in the backround).
See this: https://img695.imageshack.us/img695/764/aball.jpg
A ball is moving horizontally and it has a good MB inside. The bakcground is moving diagonally and itself has a good MB, but the outside of a ball MB is in this direction too, which is wrong.