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Pretorian
04-29-2005, 04:22 AM
Probably all of you saw Forest Gump movie. Remember a guy (can't remember the name of the actor) in the wheel chair? I saw a quick-shot of how they made that and seems they use key to "erase/hide" body parts, or whatever. There are many scenes like this, like Skinner in The league of Extraordinary Gentlemen. They use a blue/green wear. In case of Skinner, the actor was entierly covered by a green cloth. In Forest Gump they covered only the legs. I was wondering how exactly they do this. As I understand, they shoot the scene two times, one with the actor, one without, because when you "erase" the blue/green part, it must be something behind, doesn't? Is this really the way they do?



Thanks

Aruna
04-29-2005, 04:32 AM
That's pretty much it. They also used the same technique in Hollow Man with Kevin Bacon. He was in a blue suit with burn marks, and they removed the suit in post, revealing the background clean plate that they shot.

Pretorian
04-29-2005, 05:00 AM
So indeed they shoot the same scene twice? How can it be to have the same angle, the same way, etc.. two times? Shooting twice and having the same result, isn't it hard to get a good (by good a mean perfect) result?

The marks on the suit are for tracking?




Thanks

-Vormav-
04-29-2005, 06:58 AM
So indeed they shoot the same scene twice? How can it be to have the same angle, the same way, etc.. two times? Shooting twice and having the same result, isn't it hard to get a good (by good a mean perfect) result?

The marks on the suit are for tracking?

Most of the shots from Forrest Gump with Lieutenant Dan had pretty simplistic camera movements (Did they even have camera movements in those shots? I don't remember exactly), in which case it's just a matter of keeping the camera pretty much at the same point. If it doesn't match up perfectly, you can try and tweak one of the shots a little bit to match the other. But in the end, it really doesn't work out perfectly too often. They had a lot of similar effects in I, Robot, but from what I read in the Cinefex article on that, the compositors weren't able to make use of many of the clean plate shots. In which case, it comes down to good, old rotoscoping...

Aruna
04-29-2005, 04:38 PM
So indeed they shoot the same scene twice? How can it be to have the same angle, the same way, etc.. two times? Shooting twice and having the same result, isn't it hard to get a good (by good a mean perfect) result?

Well, sometimes it can be a chore. Most of the time they use what's called a motion control camera, which is a computer controlled camera that can duplicate the same camera moves many times. The drawbacks are that it's a huge unwieldy device that takes time and money to set up. What Vormav was saying about I, Robot is another option that the compers on that show did to work around the lack of a motion control rig for certain shots. If you take enough pictures of anything, you can recreate a background to suit your needs.

The marks on the suit are for tracking?

Sometimes they are. For the scenes in Hollow Man that I'm referring to, they had prosthetic burn marks applied to the blue suit, which, I think, had to replaced anyway with CG burn marks. Most of the time if you have a guy in a blue suit, you DON'T want markers, because it'll be a pain to paint out and remove the markers later.

Pretorian
04-29-2005, 09:29 PM
By keeping the camera in the same position, I can believe the key would not be too dificult, but, how would be by the camera moving? Does you guys saw a commercial from Adidas A3? Not only the camera moves but it has some interesting shots, like passing besides a man in the street, only goes to right and one goes to the left. How would this be made if a "gree/blue" guy is supposted to be wearing the suit could make this? Is it possible to be using two diferent persons, one using the shoe in one foot and one in the other?



Thanks


PS: if you wanna see the Adidas video, let me know and I try to upload it to somewhere

animquer
05-01-2005, 12:43 AM
vorman rotoscoping? what is that?

sly
05-02-2005, 10:18 AM
Try this link if you want to know more about motion control rigs, their uses and advantages.

http://www.camera-e-motion.com/whitepapers/?PHPSESSID=c6a5030a82b1a7a7364d51579ac91312


Sly

Pretorian
05-02-2005, 08:01 PM
Sly: I saw the web site but, do you mean that Adidas A3 commercial was made with motion control?
Most of the commercial I understand how was made but, the parts where the right leg goes to right and the left goes to left and a man pass in the middle, that I want to understad, how this can be made?

And, like people said here before, the scene is shooted twice, one with the gree/blue guy and second without him, that's ok if you have the shot still stand, but in this commercial you have some shots where the camera moves to follow the "actor". Are you saying that this move by following the actor is made with motion control, to have it precise?



Thanks

wizfx
05-04-2005, 12:50 AM
actually I dont think its 100% necessary to shoot the same sequence twice and try to match both cameras.
You could easily shoot the set that will be shown with a still camera, from the general angle from which the motion camera will be shooting. That image could then be tracked in fairly easily and some minor compositing magic to blend it in.
For some cases where paralax is important they could make lowpoly geometry to generally match the set and camera map the still image onto that geo.
alternatively you could use a moco rig as someone previously stated.

Aruna
05-04-2005, 03:55 AM
Woah.. Let's answer his question before we go off on a tangent and explain other ways to accomplish the commercial.

Sly: I saw the web site but, do you mean that Adidas A3 commercial was made with motion control?

Yes. This spot was created using a motion control rig. If I remember correctly I recall seeing this commercial last year, and did watch the breakdown that Digital Domain did. If someone from DD wants to step in and correct me, please do.


Most of the commercial I understand how was made but, the parts where the right leg goes to right and the left goes to left and a man pass in the middle, that I want to understad, how this can be made?

Well, if the guy is on greenscreen, you just key him out. Regardless of if there's a motion control rig or not, a key is a key is a key.


And, like people said here before, the scene is shooted twice, one with the gree/blue guy and second without him, that's ok if you have the shot still stand, but in this commercial you have some shots where the camera moves to follow the "actor". Are you saying that this move by following the actor is made with motion control, to have it precise?

IIRC, they shot the actor on a stage with him doing his moves with a motion control rig, and then in post they created the environment. Because the camera was computer controlled, they already had a virtual camera that they could use. All they had to do was matchmove the actor, or if there were tracking markers (I can't recall) they could use the tracking data to choreograph the mechanical legs to match his movements exactly.

Hope that helps!

Pretorian
05-17-2005, 07:55 AM
By matchmoving the feet, you get a control over them like if they were objects, right?




Thanks

Aruna
05-17-2005, 05:10 PM
Yes, that is correct..

Pretorian
05-17-2005, 09:03 PM
How can I increase the skills on matchmoving as I'm not very good on this? As far as I know, by practicing you achive the perfection :) but, any advice or tip?

Matchmoveing by Tim Dobbert? :)



Thanks

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