Archive:Kdenlive/Manual/Effects/Alpha manipulation/Rotoscoping
Rotoscoping
"In the visual effects industry, the term rotoscoping refers to the technique of manually creating a matte for an element on a live-action plate so it may be composited over another background." Wikipedia
Examples of what you can do with the Rotoscoping effect.
see also Rotoscoping on ttill's blog
This video is about green screen on Kdenlive but he does use rotoscoping in it too.