Scene Extension

[RFX]

The way i would do it is, try to get a big piece of green or blue screen cloth, and have it be put in some point of the corridor, blocking everything back, and then composite in a 3d model, or matte painting of the extended corridor, or if you don't have access to the cloth, you could rotoscope out a part of the corridor, and composite in a matte painting of the extended corridor.

[jussing]

The easy way:


Have a locked-off camera, as high as possible on a tripod.
Have none of your actors in front the part that needs to be extended (that'll save you the trouble of keying or rotoscoping)
To fill in the extension, either paint it in Photoshop (using a picture of the real corridor), or film a second set of actors in the corridor, and see if you can "resize" that to fit the extension hole.
Hope that makes sense. :)

- Jonas

[mArBLe]

Thanks for replies.

That was our first thought, and the only solution to this as we saw it, to use a green-screen that is.
And that's what we have thought of doing, putting a green screen at the end of the corridor (or whatever) and then build the extension in 3D with photos from the set location as the textures.

Any suggestions other than that?

[NickJushchyshyn]

If you can stage the action in the "close" area of the hall so that it never crosses in front of the distant area you plan to extend, you don't need a greenscreen. If you use a greenscreen, you'll have issues with green spilling on the the real walls and floor reflections. It's just extra trouble that you don't need.

Just make a photoshop file that's transparent in the action area, and replaces the end of the hall with the extended set, (using a frame from the actual shot as starting point for creating the PSD) then layer the photoshop file on TOP (not under) of your original shot.

Now the action will show through from under the photoshop file, but the image will cover over the end of the hall, replacing it with the set extension. BTW: Adding just a little animated noise to the PSD in your compositing tool to match the grain of the original shot will help it look "live".

Good luck.

[mArBLe]

Yeah, the green screen spilling over to the surrounding environment is definitely a problem, but how am I supposed to paint a PSD file?

I mean, it's a moving clip with a moving camera where an actor is in front of the wall that needs the extension?
Maybe I misunderstood you but don't I have to mask out everything in the foreground for EVERY FRAME that way?

[jussing]

Maybe I misunderstood you but don't I have to mask out everything in the foreground for EVERY FRAME that way?
Not if you do it the way Nick and I told you: DON'T have people in front of the area that needs to be extended, you'll save many headaches that way.

Yes, the professional way is to key the background, but professional people have expensive greenscreens, expensive lighting equipment, cameras with professional image quality (= not DV garbage colors), and people who do professional keying to do the post production.

I don't know what your resources are, maybe they are professional, but amateur chromakeying always sucks. :)

Also, don't have a moving camera.

If you insist on having a moving camera and people in front of the area, at least do two tests first, your way and my way, and then make up your mind. :)

Cheers,
- Jonas

[mArBLe]

Okay, if the camera isn't moving and there isn't any moving objects in front of the extension I can understand your way is great.

However, during this project we act as a VFX group for a real director.
Therefor the actor needs to be moving in front of the extension, and the same with the moving camera part :S

However, the quality of footage is quite good since it's on DigiBeta.

[jussing]

OK then, congrats on landing a great gig, then! :)

If you're working for a real director, the more important it is that you have tested the technique before the shoot, so you know what the h... you're doing.

If you have a moving camera, you need to do some camera tracking in post production.

So, you have to find out if you're going to do 3D tracking (difficult) or 2D tracking (less difficult).

If all the camera does is pan and tilt, but is otherwise locked on a tripod, you should be able to get away with 2D tracking, and you just need to put tracking markers on the greenscreen, just so many that you can always see two of them.

If the camera moves around, you're moving into 3D tracking, and you'll need tracking markers (preferably in measured distances) also in the area outside the greenscreen (only putting markers on the greenscreen for 3D tracking will give you a "flat" and rather useless tracking).

Do you have any tracking software and 3D app?

And what's your position in the VFX crew?

Cheers,
- Jonas

[mArBLe]

Hehe, thanks. But it's not "landing a gig" really, since everyone in my class are working for this director. Although, either way it's a good and interesting project because it's a real production.

Okay, great.
Guess we weren't that off in the first place when we discussed how doing the extension then :)
We were planning to have the green screen at the end of the corridor with tracking points both on the green screen and the environment.

We've been trying it out both with and without green screen and also tracking, and it works pretty good. However, we haven't tried to mask out the tracking points yet.
That is also something I'd like some tips at. Should I just paint over the tracking point with something from the environment? When it's a green screen I suppose I could track a piece of green on to it to make it go faster, haven't tried it out yet though.

For tracking we have PFTrack and Maya Live to our disposal and for 3D we use Maya.
I have my hands in pretty much everything related to post-production during this project.
So I guess I have the role of compositor then :) Maybe a little more, don't exactly know everything a compositor has his hands in.

[jussing]

All righty, seems like you're on the right track then. Do me a favour, post a link to the results in this thread when you're done (if you're allowed to put it online), I'm sure we'd all love to see it.

I have little practical experience in painting out things from a live action plate, but I have some. For tracking markers outside the greenscreen, you should be able to dublicate others areas of the picture to hide them. Maybe filming a clean pass without actors or tracking markers will help you, too (obviously not as perfect as if you'd had a motion control camera, but still, it might help - clean passes are often useful in compositing, even when you thought you didn't need 'em).

For tracking markers in the greenscreen, you don't need to bother duplicating green on top of them - if you're masking them manually anyway, you might just as well mask them, making them transparent.

Good luck!

- Jonas

(don't know anything about Maya or PFtrack)

[JoshKirk]

Id just roto out the actors and track 2d with some clever corner pinning since it is just a hallway. I say roto because whatever you will try to do it sounds like you will just end up having to roto it out later anyways, so save some time.

[jussing]

2D or not 2D, depends on how close the extension is to the camera, and how much the camera is moving. If the camera is moving, for instance, from right wall to left wall, the perspective of the hallway extension will change completely, and you'll need 3D tracking.

(in the prisoner block shootout in the Death Star, in the first Star Wars, you can see they extended the corridor with a flat cardboard, with an extension painted on it. This is a nice and easy solution, but you can see in certain clips that the perspective is off)

- Jonas

[mArBLe]

All righty, seems like you're on the right track then. Do me a favour, post a link to the results in this thread when you're done (if you're allowed to put it online), I'm sure we'd all love to see it.

If we're allowed, I sure will :)

We will have to use 3D tracking since the camera is moving. In one scene (for going to do an extension both ways of the corridor) I think the camera even is "running through the corridor".

Well, shooting today so :)
Hear from you later.

[mArBLe]

Hey, the project is finished now (actually has been for quite a while now, I just didn't find this thread again until now).

So I just wanted to post the finished sequence and hear what you guys I think.
I did all the tracking (first tracking ever, pretty fun to work with) and also all particle effects.

Download here: http://www.fugixi.com/vfx.avi

[JoshKirk]

My computer wont play the file... do I need some special codec or something?

[mArBLe]

The latest XViD version should suffice.

[CGTalk Moderation]

This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.