It's actually a complicated effect, depending on the look you're going for. If I were doing it, I'd just shoot the talent on a bluescreen and then rotoscope the frames in which they pass through the wall. There must be shortcuts to this method, but I can't think of any at the moment.

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Andrew Gingerich
Exploding Goldfish Films
Check out my vodcast on iTunes: http://phobos.apple.com/WebObjects/MZStore.woa/wa/viewPodcast?id=96931870
and my blog at http://www.exgfilms.com

Ahhh, sorry my question wasn't very clear now that I read it. For example say you have some talent on second floor of a building and someone is downstairs. How would they go about filming so it appears as though the camera goes through the floor if you were going from the person on the second story to the person on the first? If you need any more clarification just post a question. Thanks.

Ohh? I understand now! This is usually done on a stage-built set with an actual cutaway (They did this with the boat in The Life Aquatic), but one cheaper method is to just have the camera pass behind something to black out the lens and then bring the camera back out from behind it on the other side of the room/floor, repeating the move. When properly done, it can look pretty good.

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Andrew Gingerich
Exploding Goldfish Films
Check out my vodcast on iTunes: http://phobos.apple.com/WebObjects/MZStore.woa/wa/viewPodcast?id=96931870
and my blog at http://www.exgfilms.com

I figured thats how they did it. Thanks for the info agingeri.

Another fun thing to do (got this from the Simpsons) is instead of just having black as you go through the walls, flash by a small hidden something in the wall. An old skeleton, buried treasure, rats, depends upon your genre and the seriousness of the movie. This works best if done fast so people know its not something they really have to have noticed to 'get' the movie.

RJSchwarz
San Diego, CA

Good 'ole Simpsons. Thanks for the post rjschwarz