Video by via Dailymotion
Creating a mask transition will get an impressive feeling between footage in few seconds.
First step, select the frame of the clip where you want to start the transition and go to fusion.
Second step, add the tool Polygon and activate the Invert.
Next step, you have to mask your subject and do this frame by frame, this will take a little bit time Last step, move the second clip under the first clip and done!