Overlay/Mask/Layer Question

[legocrazy1]

So I've been reading more and more in the forum, and even after a simple search I couldn't find the answer to this problem. I'm sure the topic has been brought up before though.

I have been curious on how one can create a sort of cloning effect in a video. Say the camera stays stationary and the object in the camera does some action. Then they change positions and do something else. When they finish editing it looks like both events happen at the same time.

I was looking through avisynth functions and filters and I almost want to say it is quite possible to do, and there's probably a very simple solution. It might be more than one function, but still simple enough.

I'm guessing it has to do with overlays for the most part, and maybe some subtraction and chroma keying, but I really don't know.

-Adam

[redwudz]

Do you have a clip that illustrates what you mean? You can link a YouTube video here. If you are asking about some of the effects in a movie like 'The Matrix', some of that is shot with multiple cameras surrounding the subject.

[fitch.j]

If your doing it with a camera that hasnt moved its a simple as a split screen. Depending on how complex it is this can either be done with something like a wipe (if each action is performed in a way to not corss into the others 'space') or an animated mask to be more accurate. For real complex compositions you may need to Roto sections of it, for example if you need to add depth when one may go behind another, or if they interact with each other.

[edDV]

In the analog switcher days, this could be done with a "non-additive mix". Basic rule was the mixed object had a higher luminance than the background. in other words, at the pixel level, the brighter of the object or background is passed 100%.

These days most would use a green screen.

Here is a digital composite version.
http://www.digitalfilmtools.com/cs/nonadditivemix.htm