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Old September 15th, 2007, 02:54 AM   #1
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Extraction Help

What is the fastest way of extracting these people and the car off of the background? I need to make them look like they are flying down a mountain side with trees whizzing by them.

http://s32.photobucket.com/albums/d1...current=13.jpg

I have 176 frames to do and I don't want to roto them out. Is there a better/faster way?
Alan James is offline   Reply With Quote
Old September 15th, 2007, 05:41 AM   #2
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A couple of questions.

1. Is the car moving (being rocked back and forth to create the illusion of movement or actually driving) or stationary?
2. Do you have a clean plate of the background without the car there?
3. I noticed a hand coming outside of the car is that hand also moving or is it pretty much stationary?
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Old September 15th, 2007, 09:32 AM   #3
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Good questions, Mark. Keying the parts of the background appearing through the inside windows is going to be a ****. Plus there are reflections on the car that are not going to move as they should when you replace the background. I would reshoot with a proper screen behind them, or even just a blue sky. That would be the fastest way.

Keying the exterior is the least of your worries.
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Old September 15th, 2007, 10:40 AM   #4
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If there is a lot of movement in the scene, there will be no chance of anything but roto.

And if it is mostly stationary, the roto will be very easy.

Perhaps you could try a difference key (with a clean plate, either shot separately, if you did that, or created from various frames as a still). However, any noise, etc., will make that option very difficult. Difference keying is rarely very clean, from my experience.

The hand will need to be rotoed, almost surely. That's not too bad though.

The above post is quite true. You will have very serious problems with the integration. You should add some highlights around the surface of the car.

I'd suggest recreating as much of the car as you can digitally, then projecting parts of the background at low opacity and blurred.

The most difficult part of the process will be the interior, with the windows. Again, recreating these with layers will help a lot. Much more work there, than just rotoscoping the exterior.

Roto is boring and tedious, but quite possible. The rest takes a lot more work.

If you post the footage, we could give some more input.

Really, 178 frames isn't so terrible. If you can't reshoot, just do it. No big deal.

I'm currently working on a project with some shots much worse than that, and I completely understand not being able to reshoot. But if you can, good idea.
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Old September 17th, 2007, 03:50 AM   #5
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My internet has been down all weekend and this is the first chance I have had to reply.

I don't have a background plate. The car does rock. We didn't have a screen big enough to put behind the car at the time, and the actors live in another city and cant come back for one shot. I guess 178 frames isnt that mant to roto out but I HATE IT. I will never be a roto artist because I dont have the patients to work on it for hours. I can barely wait for my renders to be done and thats just me sitting around.

I was dreading the inevitability of it but knew that eventually I would have to roto it, I kinda just needed someone to tell me.

I am making a green screen movie and This is one of 140 or so shots. All the others just need keys and minor roto work. This one will be the hardest shot for sure.

Thanx
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Old September 17th, 2007, 09:02 AM   #6
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If it isn't moving, then you have very little to worry about. Rocking is alright; just find the ends of the motion and add keyframes. You can also track to a moving car.*
Again, consider replacing as much of the frame with stills as possible, then matching the lighting on those.
Extracting the actors from the background seen through the windows will be the most difficult part (rotoing the car will be easy, and his hand will just take some work if it's moving a lot).
Then, of course, the challenge will be blending. Good luck with that. Maybe you could add some snow on top of the scene to make it feel more like they are there. Not sure what else you can do, aside from lots and lots of manipulation.



(*Depending on the FX app you're using, you may be able to track the masks. In After Effects (if that's what you're using), there is no option for this, but there's a way around it. Make a mask on the first frame on a null layer that matches the shape. Then track the null to the car layer, and the hole it cuts is the mask you want. Some manipulation, then, of the mask at certain points will make it a fairly simple job. This could help in some other apps too. Note that you can use the track matte option to apply this.)


Another approach which might actually end up easier would be to change the shot entirely.
1. Stabilize the footage (including rotation).
2. Recreate the car around them, including more than is on screen.
3. Use some images of the background to create a workable 2.5D environment for some creativity.
4. Do some tricks with the camera to keep it a bit farther from the actors.
You could, for example, do a long zoom, or place them into a moving car with a stationary camera, so you only see them up close for a few seconds.

I gotta say.... it sounds like kinda a fun shot to play with, though I don't envy you in having to make it look completely real in the end. Look at it as a challenge, though. I still wouldn't mind seeing the footage.
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