Tracking / Roto Problem - Any Suggestions Please

Compositing
1

I have a shot that pans with a character as they pass in front of a greenscreen window. The window is divided up into various geometric shapes...(guess what - its sci-fi!). I am not doing the composite, merely creating the rotoscopes and mattes. The green screen is not good enough to just use a keyer - i'd rather have the sharp clean lines of a rotoshape if i can.

Because the camera moves as well as pans there is a degree of shape changing involved. I would like to be able to create a rotoshape that matches the windows, and then attach each roto point to a tracker, which has the relevant track data from the shot. The hope being that i can use the track points to accurately dictate the shape of the rotoshape at any given frame.

If it were a four cornered window i would use a corner pin and stabilise node, but these windows have more points. I spent a long time trying to achieve this effect on a previous project but could not get it to work satisfactorily (I wanted each rotopoint to lock to its relevant trackpoint so that the rotoshape would distort to match the real distortion over the duration of the shot - but it didn't work) , so i'm hoping someone could give me an idea how to create an animating, tracking rotoshape.

sorry if i'm rambling, its got me really puzzled and i'm not too sure if i have made a clear and concise description of the problem.

thanks
adam

2

if you track the points or joins in the windows you want to roto, you can then attach trackers to individual rotoshape points, that is if you are using shake 4.x

this should do what you are after.

You could also try just going from starting roto shape to finishing rotoshape, but it sounds like the moving of the camera will not let you do that.

after you have tracked the points you can always move them to realign later. but either way it looks like it could be quite a bit work.

Curses.

3

"if you track the points or joins in the windows you want to roto, you can then attach trackers to individual rotoshape points, that is if you are using shake 4.x"

already tried that and it doesn't work. I can get one or two track points to remain connected with the rotopoints but the other rotopoints just drift off track ('scuse the pun!).

Is this a limitation of shake? or is it just me doing something wrong?