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Author
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Topic: How does a CGI character walk BEHIND an actor?
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Mr. Hutt
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posted 12-23-2000 08:29 PM
I've been wondering this for a while. In most films today that involve CGI, there are shots where a CGI character will walk behind an actor. How do they do this? It's obviously not manual rotoscoping, because they're able to maintain every detail on the actor! In SW1 when Jar Jar walks behind Qui-Gon, every nuance and detail is kept, even stray hairs waving around! It's as if the actors were in front of a blue scren, but I know they're not, because you see all those "before & after" clips in Making Of specials, and they weren't blue or green screened. HOW do they do this?? ------------------
Mr. Hutt -defender of neenerheads |
tigerquoll
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posted 12-23-2000 08:56 PM
Check out the z-cam http://www.3dvsystems.com/products/zcam.html Don't know if this is what they used in phantom menance but these distance measuring systems do allow you to create depth masks. Makes blue screening redundant. Wonder how many years it will take for this sort of stuff to hit consumer level cameras? |
Movieman21
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posted 12-23-2000 09:25 PM
Most likely it was just done in layers. The background was probably one layer, then the CGI, the the live shot sequences. To get an idea of this concept, merely explore Photoshop. Whenever you PASTE something in, it is put on a new layer. If you click the layer options, you can actually arrange the layers. Something that was origianally in front, you can move to the back, and visa versa. If you fool around with it, and get the hang of it, you can create some pretty amazing effects. To use this in film, you would have to do this frame by frame, as FLM files, but if done right, looks very good.------------------
"May the Force be with you." Be sure to check out JRMorgen Productions ONLINE, at http://hometown.aol.com/jrmorgenfilms/
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Buddy
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posted 12-23-2000 09:47 PM
Shoot your actor in front of a green screen then render your cgi guy walking with the background pic behind him then chroma key out the green and leave the cgi man and background behind. ------------------
"That's not a knife, THIS is a knife".
"No it's not. That's a spoon". "Ach. I see you've played knifey-spoony before".
http://www.members.tripod.com/b-mage |
multimedia light & magic
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posted 12-23-2000 11:38 PM
it's just that easy!  |
Film Boy
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posted 12-25-2000 03:44 PM
I'd never heard of the z-cam thing but that is very cool. I think Mr. Hutt's question is about the isolation of an actor to then be layered, and not the fundamentals of layering, right? Well, there's this other thing called knock-out I've seen and it basically rotoscopes stuff. You draw keyframed outlines and the program cleans it up and makes it nice and removes that person for later reinsertion. They may have used this. |
NJRFilms
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posted 12-26-2000 12:03 AM
i remember seeing a makign of EP1 and they had a guy in a blue suit walking around and saying the lines of jar jar during filming... Might have just been to help the other actors though, not realyl sure. |
Film Boy
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posted 12-26-2000 02:12 PM
Yeah, I think what that is is before shooting or just for just a couple of takes he would be in it to give the actors, as well as ILM a refrence. |
Chimpoid
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posted 12-26-2000 06:04 PM
Nothing as long winded as that im afraid. Just shoot the actors and then use that as a backdrop for the cg render. Matte materials allow you to draw the background into the foreground in front of the cg.Chimp |
tigerquoll
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posted 12-27-2000 08:58 AM
If you were using actors filmed against a real background then you could use a difference matte function like the one in premiere. With your camera locked down first film the background without the actors. Then film the actors in front of the background. Using the difference matte you can make a mask of anything that is different in the two sequences. Done properly the mask should match your actors and could be applied to your cgi character. |
