Need to add moving shadows to footage

[Abaddon]

I green screened a guy who will need to appear as if he's traveling through the woods. Since there are so many shadows created by the surrounding trees, I need to simulate a similar effect onto the subject, where the shadows could hopefully match hit contours.

Are there any good effects I can use to at least get close to something convincing?

[mail4joeg]

If you haven't shot it yet, here are a couple of things to try.

Note the exact specs of how you shoot the background: height of tripod, lens (pref. prime), focus. Get a reference subject too. A person and/or billiard balls are often used by VFX people. It sounds like you may have the light coming in through leaves of trees above from the sun. --Question, why can't this just be shot in the woods without a green screen? Anyway, simulating the leaves / light from above may be difficult if you can't get the leaves up high enough above the subject to match. And you'll want them moving around making gently moving patterns like with a fan. The green screen itself can be done outside with real sun, so you have the same light source. It may need flagging for bounced reflections and shooting at the same time of day, etc.

[Abaddon]

Sorry, I should have given more details. The guy is flying through the woods so we had to green screen him. We didn't have the capability of using real shadows from the trees. I shot the footage of the movement through the woods, so I just need to match the green screened guy with the background. I imagine I can use some kind of flicker to simulate the changing of light patterns, but I was curious if there was a more effective method.

[Cassius]

The more effective method would have been to light the subject completely independent from the green screen and have shadows pass over him during the take by waving things by your lights. If you want the shadows to look real a reshoot is the only realistic solution. Flicker is not the same thing. Contours can really only be matched by computer graphics if you have a 3D model to wrap it around, which would be way harder.

[Abaddon]

Re-shooting is not an option. I have to work with what I have.

[Abaddon]

The effect doesn't have to be perfect, just something a bit more convincing.

[kennedymax]

One can't be half pregnant. It either works or it doesn't work. "A bit more convincing" doesn't get it. If it doesn't work re-shoot it the right way, (as above), or chuck the idea. Maybe get someone to shoot it who does knows how.
Good luck,
Ken

[Abaddon]

I'm not friggin making 'Avatar' here. It's okay if the effect is a bit cheesy. Any added realism is a plus. If no one has any suggestions, fine.

[kennedymax]

Why don't you put your background scene on V1, you greenscreen scene on V2, then repeat your greenscreen on V3 only this time fill the key with a panned soft focus shadow scene over your actor and adjust this key to taste. And if you really want to be cheesy (or campie) have its motion move backwards.
Have fun.
Ken

[MichaelC]

If you have access to After effects, it would be pretty simple to add a layer over your main scene with any sort of shadows you wish. You can create the effect by using a light layer over a layer of random objects. Set all the layers to 3-d (classic is go enough), then tell the "leaves layer" to cast shadows. Then tell AE to only show the shadows from that layer and not the objects themselves. To move the shadows, you can animate the whole thing in a loop and make the time line as long as you want. If you don't have After Effects call somebody who does and have them create the loop for you in what ever format you need for your post software.