Help with layer compositing

Sebaz wrote on 12/12/2009, 6:34 PM
Let's say I have one camera on a tripod, shooting completely still, and a person walking around in different places of the frame. At some points he is towards the left of the frame, at times, on the right. Now, I would like to use multi-layer compositing to make that subject appear on different places of the frame at once. I know that I could just make a mask to the upper track and cut the frame in half, to show the subject at least twice, but I was wondering if there is another way where Vegas can simply erase all the pixels that are exactly the same as in the lower track, and just leave the subject moving in the upper track, or tracks. I tried all the different compositing modes, both making the lower track the child and without, and I can see some interesting effects, but not what I want to achieve.

Is it possible to do this?

Comments

rs170a wrote on 12/12/2009, 7:06 PM
See if this tutorial helps.
Two Cats From One

Mike
TeetimeNC wrote on 12/13/2009, 7:01 AM
Sebaz, theoretically Difference Masking will do what you want, but my past experiences using SD footage were marginal at best. Might work better with good HD footage. However, I think your "cut the frame in half" approach will likely be easier and better.

Jerry
farss wrote on 12/13/2009, 11:36 AM
I've used difference masking with footage from my old SD D8 camera with quite good results. You really must have the camera locked off, move it a pixel and you're dead. Need to watch shadows and noise is a killer.

Bob.
JohnnyRoy wrote on 12/13/2009, 5:02 PM
> You really must have the camera locked off, move it a pixel and you're dead.

Not to mention it must also be in full manual mode with the exposure locked off as well. Any change in exposure and you'll introduce more headaches.

My vote is for masking. Way quicker and easier unless the subjects need to cross each other. Then a difference mask is the only way.

~jr
Rory Cooper wrote on 12/14/2009, 12:22 AM
You can comp a few layers together to achieve what you want using lighten this works well on a lockdown cam with the background underexposed
Or otherwise use add and set levels on tracks to compensate for overexposure

A b roll clip lightened and playing around with position on each track http://www.myvideo.co.za/channels/xfx
Excuse the audio but MV often screws it up

Rory