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Parallax with boujou greenscreen matchmove in after effects

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Carl JacksonParallax with boujou greenscreen matchmove in after effects
by on Sep 6, 2009 at 2:42:39 am

I recently tried to shoot a handheld greenscreen shot. I wanted to composite elements into the backgruond with parallax so I needed a virtual camera move in after effects (cs3). I used boujou and did a simple matchmove and got the correct camera move. When I imported to after effect as a .ma and composited the background in 3d space in front of the camera, but no matter how far forward or back i moved the background in 3d space it simply looked like it was motion tracked to the greenscreen footage (no parallax). I dont know if this has any thing to do with it but the camera that was imported had no point of intrest. Well at this point this is getting to be a pretty long post, but anyways any help at all would be appreciated.


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Dave LaRondeRe: Parallax with boujou greenscreen matchmove in after effects
by on Sep 8, 2009 at 3:00:29 pm

Does the focal length of the AE camera match the focal length of the hand-held camera?

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Dave LaRondeRe: Parallax with boujou greenscreen matchmove in after effects
by on Sep 8, 2009 at 3:37:43 pm

Oh, and to be perfectly clear on this: you DO have 3D layers in this comp with the camera, right? Layers that are indeed in different positions in 3D space and would display different characteristics as the camera's focal length changes, right?

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Carl JacksonRe: Parallax with boujou greenscreen matchmove in after effects
by on Sep 9, 2009 at 1:28:49 am

A. The original greenscreen footage is on a 2d layer in front of everything, the background layer is on a 3d layer
B. I do not understand what the "focal length" is you are talking about.


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Dave LaRondeRe: Parallax with boujou greenscreen matchmove in after effects
by on Sep 9, 2009 at 2:54:08 pm

[Carl Jackson] "A. The original greenscreen footage is on a 2d layer in front of everything, the background layer is on a 3d layer "

So the chroma key subject appears to be drifting against the background, and it doesn't have a whole heck of a lot to do parallax then, right?


B. I do not understand what the "focal length" is you are talking about.

Some valuable reading:
http://en.wikipedia.org/wiki/Focal_length
http://www.photoaxe.com/understanding-the-lens-focal-length-and-aperture/
http://help.adobe.com/en_US/AfterEffects/9.0/WS3878526689cb91655866c1103906...

In the Adobe reference, Focal Length is one of the last properties on the list. But it comes down to this: if you didn't know the focal length of the camera when you shot the green screen (20mm? 75mm? 125mm?), getting the AE camera to match it will be a hit-or-miss process.



Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Carl Jackson Parallax with boujou greenscreen matchmove in after effects
by on Sep 9, 2009 at 8:36:49 pm

Actually the problem is the back ground is not drifting.
Maybe im doing this a hard way can you tell me how you would do a hanheld chroma key shot with parallax?


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Dave LaRondeRe: Parallax with boujou greenscreen matchmove in after effects
by on Sep 9, 2009 at 9:00:17 pm

I think some signals are getting crossed here, so could you do us a favor? Could you tell us in Plain English -- no technospeak allowed -- what you mean by the term, "hanheld chroma key shot with parallax"?

How are you moving the camera -- jumping up & down, running in & out, moving side to side? What sort of image are you putting in the background? After you've done your AE voodoo, what do you want the picture to look like to the viewer? Should the viewer be able to see around a corner or something as the camera moves?

Creativity and CLARITY in your response counts. Think about what you write before you write it. You will be graded on it.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Carl JacksonRe: Parallax with boujou greenscreen matchmove in after effects
by on Sep 9, 2009 at 9:55:04 pm

I have a shot of an actor on a green screen (with track points)that is not taken with a tripod it is a little shaky and I do not want to stabalize it( for realistic purposes) . When it is finished i want the back ground to look far off and not be perfectly tracked to the shaky handeld moves of the actor (like it would in real life). the camera moves are all 2d i just used boujou (3d tracking software) to simulate a camera move. So how would you go about doing this?


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Dave LaRondeRe: Parallax with boujou greenscreen matchmove in after effects
by on Sep 9, 2009 at 10:51:32 pm

[Carl Jackson] "i want the back ground to look far off and not be perfectly tracked to the shaky handeld moves of the actor (like it would in real life)"

Sorry, but in every hand held shot I've ever seen, the background and the foreground move together.

I'll give you a C-Minus to a D-Plus for the reply. Why not a higher grade?

Because you neglected something very crucial -- you didn't describe describe WHAT THE BACKGROUND IS.

Is it rolling video of a city street or a busy office? Is it totally built out of graphics & layers in AE, using a combination of effects? Is it a photo montage? Should these photos in the montage look like they've been piled up one on top of another, or nicely placed along a wall, like pictures in an art museum? Is it space station? An open field? Does this background have depth to it, like a long tunnel? Is it planar, like a bookshelf or a wall in the living room?

Each of these backgrounds requires a different approach in AE to pull off something that looks convincing. Who knows, you may not even WANT it to look convincing!

But you get the idea now, I think -- you need to elaborate a lot more... and I'd better stop writing before I change your grade downward.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Carl JacksonRe: Parallax with boujou greenscreen matchmove in after effects
by on Sep 9, 2009 at 11:06:57 pm

Thanks for the grade I'll work on my clarity skills. The background is a photo of mountains in the distant background, but if i perfectly track the backgorund to the greenscreen footage it looks like the actor is simply standing in front of a the photo or a wall with the photo on it.


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Dave LaRondeRe: Parallax with boujou greenscreen matchmove in after effects
by on Sep 10, 2009 at 3:25:13 pm

[Carl Jackson] "Thanks for the grade I'll work on my clarity skills."

... and thank YOU for accepting it in the spirit in which it was given. Now I know that you're looking for a background where things that are close move more than things that are far away. This is a technique used in the film, "The Kid Stays in the Picture". You also see it in some historical photos where the camera moves on a picture from the 1800's, but it looks like it's 3D. And if you don't know Photoshop, find someone who does.

This isn't going to be easy, but it'll look cool. Frankly, depending on your AE & Photoshop knowledge, skills and experience, you may find it beyond your capabilities. You need to know that going in.

You're going to do two broad things: 1) Create a main comp with your chroma key layer and a nested comp which contains your background 2) create the nested comp with your mountain picture cut up into many layers, plus the 3D camera animated by the Boujou data. The main comp is a piece of cake; it's the background comp that's tough. So we'll start there.

You'll want to cut up your background in Photoshop into several layers: close-up objects, middle-distance objects and distant objects. For close, middle and distant, you'll need three layers.

Cut these objects right out of the background picture and put them on their own layers in photoshop. Then in the holes you've created, you'll need to recreate what would have been there if there had been no object. For example, you cut out a tree in a grassy field -- you need to put grass into that tree-shaped hole.

once you have your layers done (that's the tough job), import the photoshop document into AE. Add the layers to a comp, and make them 3D. Add a camera, and in its initial control doalog box, make its focal length about the same as what you used on the camera when you shot hand held. Separate the layers in z-space, and play with each layer's scale until it looks right again. Now parent them all to a 3D null object. Apply the Boujou data to the camera.

Now when you nest the background comp in the main comp, it should do what you want it to.

I looked for tutorials on the COW for this, but couldn't find any. There may be some on YouTube or some place like that. Just google "The Kid Stays in the Picture", and you should get a good start.

And good luck.



Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Carl JacksonRe: Parallax with boujou greenscreen matchmove in after effects
by on Sep 11, 2009 at 11:27:02 pm

Thank you I will try it and get back to you on how it works


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