Camera Move Tracking

[Gohanto]

Hi, I'm looking at doing a fairly complex stunt but I'm not sure how to do it in After effects.

The goal is to have a shot of someone fire guns while falling off a roof. The camera pans around them during the firing. I can keep a green screen behind them throughout the shot, and in behind-the-scenes clips on DVDs I've seen people using white dots on green screens for reference points so they can line a movie background image with them. How would you do something like that in AE?

Thanks.

[graymachine]

This isn't really a job for AE. If you key out the background, and motion track until the cows come home, that won't give the ability to have the camera pan around the actor.


You'd need some heavy duty camera equipment (camera ring) or a CG actor to pull this off well.

[Steve_Arm]

There is this scene in Matrix 2 where Trinity falls and fires with 2 guns and the camera travelles in reverse. In the making off (2nd disc) you can see how they did this to get some ideas. You need rails and other stuff.

[oneinfiniteloop]

Like Graymachine said, this take a serious camera rig to pull it off how you see it in your head. Unless you have 30 or so dSLR's or a very high speed camera lying around, I would suggest taking a different approach.

[Matt Grunau]

In the situation you describe, the only part AE would play would be in compositing. Those dots to which you refer, especially in this case, would be used by a Boujou type match moving software to track the dots into 3D data to be used back in a photorealistic 3D scence in which the camera data from the tracker can be applied. The the 3D camera creates a pass, and the live action is placed on top. It would have to be a 3D scene rather than a simple background plate because of the kind of movement you describe.

There are plenty of behind the scenes footage where you see those dots on a greenscreen, and yes, those can be used to a degree to motion track a background, but you will notice in the shots like that, the background is rather static, and dynamic camera moves are not involved.

Apart from building the entire scene, actor and all, in a complete 3D environment, you are going to have one hell of a time pulling that off even semi realistically.

Make the camera move simpler. Instead of the camera rotating around the actor, film it from a few different angles and then cut between.

[surf]

and you will need a huge green screen and wires...

[kai]

The goal is to have a shot of someone fire guns while falling off a roof.

how about you... film someone firing as they're falling off a roof? :)

get a stuntman and a huge landing bag at the bottom and call it a day.

[Steve_Arm]

You mean him shooting the other guy while he falls from the roof? :kali: