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Matching footage to CGI

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Kevin Burke
Matching footage to CGI
on Jun 23, 2011 at 10:36:09 am

Hi,
I'm a motion graphics artist working on a commercial whose production is going in an unusual order...the CGI will be created BEFORE the live footage is shot with an actor. I would like to find a good method for matching up footage with the CGI graphics. I really don't know how to do this- are there any kind of existing setups that will do overlays of the footage to match camera angle & perspective?

Thank you!


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Ken Maxwell
Re: Matching footage to CGI
on Jun 24, 2011 at 9:59:02 pm

I hate to say it but, in my opinion, whomever specified the work flow for this project has it 100% wrong. One has great flexibility in matching computer art to photography, but much less flexibility in matching photography to artwork.
First, perspective can be infinitely varied in artwork. Even distorted for effect. Perspective matching is heavily restricted in photography . . . and you can't freely distort the image to match any variations to that produced in artwork. Perspective in photography is determined by lens and physical positioning of objects within the stage area. This is many times uncontrollable in exterior shooting (mountains, trees, rivers and lakes, and buildings, etc. You have a bit more ability to position props in a studio shoot.

Secondly, lighting and colorimetry can be infinitely varied in artwork (over-all as well as within the scene). Not satisfactorily so in photography without it being an enormous lighting challenge.

If you must proceed in matching the photography to artwork I suggest you make a simplified, line-art file of the artwork. Feed it, along with the camera video into a switched. Superimpose the artwork over the camera video, view it on a high quality monitor and proceed to position the camera and prop items, along with lens experimentation, and match it up.
Lacking the availability of switcher/monitor equipment, you could make a "cell" copy of your line art (sized to match and register with the camera viewfinder), tape it to the viewfinder and proceed to match everything up.

Frankly, this is not the best way to accomplish you objectives. Obviously it is easier to adjust the artwork to make a match.

Rots 'a Ruck,
Ken


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Kevin Burke
Re: Matching footage to CGI
on Jun 25, 2011 at 6:29:40 am

Thank you for the response, Ken. Yes, I definitely agree about the wrong workflow. I voiced my opinion but this is the way it has to be done for this project :-/ Your idea about the switcher was good - in my ignorance, I was considering printing the 3D graphics on transparency film and putting it over the monitor :-P I'm sure that would have been VERY precise :-D Hahahaha

Thanks again!


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Andrew Rendell
Re: Matching footage to CGI
on Jun 25, 2011 at 10:34:13 am

I suppose the things that are going to be important are the height, distance from the subject, direction (up/down as well as side to side) and angle of view (focal length) of the camera. So if you took that information from your graphics program and duplicated it to the camera setup when filming the actor you'd be pretty close to start with.

[I composited an item a few years ago where they took those values from the green screen shoot and matched them in the gfx render and it slotted together very nicely.]

I'd want to do an overlay of some kind at the shoot as well to be sure though.


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grinner hester
Re: Matching footage to CGI
on Jul 16, 2011 at 4:05:11 pm

Not sure why the powers that be want to increase budget and decrease the quality of the finished product but You can always bring out and old school switch and do cross dosolves as ya shoot.
I'd probably hire a kid nobody knows to do that and stand in the shadows due the obvious embarrassment involved tho. ;)

Sometimes in a pre pro meeting it's a good idea to just say no, we're not doing it that way. Kind of what pre production meetings are for, man.



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