3D and Video blue screen..

[jussing]

Based on both personal experience as well as watching what other people have done, I dare claim that keying on video material always sucks.

Even professional high-budget TV shows have crappy keying. Hell, you still see bad keying in some big-studio 35mm feature films with millions of dollars for visual effects, so.... keying isn't to be taken lightly. ;)

The only "easy" keying scenario that comes to my mind is if you can downscale the material - IE, if you film your characters fullscreen, but scale them down to place them on billboards or alpha planes in a larger environment, then you can get rid of the worst artifacts and bleeding, simply because you lose the troublesome pixels in downscaling.

Other than that, the most obvious thing is to light your subjects so they match the environment - consider lamps, windows, shadows etc (which if of course extra difficult if you want to create a generic library of keyed people). Have them interact and do logical things - open doors, sit at desks, etc. Don't just populate the environment with random scattered people.

Lighting the chroma background evenly is also obvious, but easier said than done. Make sure it doesn't fold, etc...

- Jonas

[shadowedge]

This isnt a difficult task... As far as i know almost all compositing software can key out colors. :)

make sure your real footage is well lit. and as much as possible it should have the same camera movement as your 3D material.

put the 3D and your real footage onto the timeline.

with the real footage selected: choose effect > keying > color key.

that should do the trick, of course you have to tweak the values to get the desired result.

hope this helps.

[Aruna]

This isnt a difficult task... As far as i know almost all compositing software can key out colors. :)

with the real footage selected: choose effect > keying > color key.



Wow.. Is it that simple?? Not to be an donkey's rear end, but this is where problems arise, when the solution to a bluescreen or greenscreen is to just key.. There are seldom times when you can get away with just one key and have it look good. There are a bunch of tricks to help the foreground keyed item sit into the background.. Of course, if you don't care about integration, then a simple key will work.

Just some questions to get you thinking..

)Is your 3D moving? If it is, you've just made your life a lot harder to get the real people to sit in the environment. Probably the best thing for you is to shoot your greenscreen people first, and then matchmove the 3D to that.
)Is your greenscreen/bluescreen evenly lit?
)Did you light your actors similar to how the 3D environment is going to be lit?
)Are you shooting on film or video?

Of course, a storyboard or previs is probably the next step in figuring out what's next. Planning for this sort of thing is always crucial.

[jussing]

Wow.. Is it that simple??
Never.

- Jonas

[A_Ghost]

Just to add my 2 cents worth -

Matchmoving your CG background with live-action can be a nightmare ...BUT it can be used as a very helpful tool in achieving better realism. Here's what I would suggest;
Shoot your live-action pieces as lock-offs(if your GS is big enough). Keep everything contained within the GS borders. Then, once you have them keyed out ( yes, I agree, video keying sucks - interlacing kills keying (remove one field - if it's 2/3 pull down from a 35mm convert then its much easier), take that footage and map them on to flats in your 3D scene (self illuminate them. Your lighting should already match, as mentioned above). Then move your camera. Keep in mind these are flats - rotating camera moves are off-limits! Dolly or pan will work well. It will give a sense of reality, and they will be perfectly match-moved (because they're actually in your scene! A little hand held movement, rendered with blur turned on, will take care or some noticablly bad keying. See www.hugglers.com (http://www.hugglers.com) for an example - look at the trailer. Mind you - we shot that with an HD camera - but the same principle was applied.

[fredz21]

My advice, you may take it with as many grains of salt as you may wish, start off with a goot set of storyboards. From there you'll have a clear idea of what you guys will want to pull off. This will save you, and your actors, camera guys a lot of guess work when you've got the talent in front of the blue screen. Interaction is te key, so think of interesting and unsual scenarios with your characters.

From experience, a combination of hand held shots and static shots seem to work very well. Keep in mind the trackers - minimum you should have 7 on each axis on screen for a good track. Blurring the images a bit helps a LOT for the troublesome pixels the spill in ;)

As far as keying, good compositing programs have good keyers. You'll have to mask out the trackers, take that into consideration. What software are you guys using? I personally prefer combustion for keying and after effects for animated masks, then again, my compositing experience is limited to combustion and after effects - the discreet keyer > keylight :)

Let us know how this project comes along

-.fredz

[bartrobinson]

( yes, I agree, video keying sucks - interlacing kills keying (remove one field - if it's 2/3 pull down from a 35mm convert then its much easier)

take that footage and map them on to flats in your 3D scene (self illuminate them. Your lighting should already match, as mentioned above). Then move your camera. Keep in mind these are flats - rotating camera moves are off-limits! Dolly or pan will work well. It will give a sense of reality, and they will be perfectly match-moved (because they're actually in your scene!

I'd have to disagree with the first bit. Video keying sucks because of three things. No one spends the time or the money to do it right. Just because video is instant doesn't mean the preparation should be. Compression is a problem. If you can, shoot with as little as possible. As for the interlacing. DO NOT drop one of the fields. That's half your detail! Seperate the fields, key, extract, comp, and reinterlace them seperately using the same settings if your comp software doesn't do it for you.

Also, whatever keyer/software you use. Don't try to pull the key in one pass. Build up the matte working on difficult areas separately.

As for the perfect matchmove, just because the card is locked down in the scene doesn't mean what's on it won't move or exhibit it's own parallax. Pans may work fine, but beware of a dolly because of parallax. People pick up on that fast if the action isn't fast paced.

Finally it sounds like you are doing what Sky Captain and the World of Tomorrow AND Sin City both did. Read up on those fx.

[Studev]

It's not easy but it's not that hard either. It's can be done work !

I hate to key something that is lit with bluescreen. My personal experience mostly used with HD. Sony Cinealta 4:2:2 is not suitable for keying where the noise is all over the place. Have ever consult with the camera expert and they don't recomend it. I think it will be easier for you to shoot on green screen, it's a better channel to work with rather than blue due to its weakest channel of all. I hate noise.

Most Film DOP that i've work with can lit a very well bluescreen when they work with 35mm. So i've almost no problem with it most of the time.

PS. I use Primmate for most of my key. It has more control and reliable compare to others.

Regards

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