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Green Screen / Camera Tracker / Plates Question

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Sean MortonGreen Screen / Camera Tracker / Plates Question
by on Oct 11, 2011 at 4:07:32 pm

Hi everyone.

i just purchased camera tracker for green screen work. i moved around
my actor with him at the centre of the image rotating around him.
i then tracked the markers on the green screen in camera tracker. I
keyed out the actor then placed the actor in 3d space. i created a 3d
background plate in AE. I then parented the background plate to
the CameraTracker Camera that was added. it seemed to work. However, i
notice that most people parent to an added NULL object on one of the
markers . Did I do something wrong? will i have problems with doing what I did?? is there a general principle for making the background plate the most realistic. I put the actor in front of the Tokyo Skyline but would also like to put the actor in a 3d room/space.

Sean


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Tudor "Ted" JelescuRe: Green Screen / Camera Tracker / Plates Question
by on Oct 11, 2011 at 4:14:51 pm

I am a bit confused, why are you parenting the Background plate to the Camera? Camera Tracker will give you a camera solve that will make your virtual AE cam to move the same way your real camera moved. So you should just adjust the background in the position you want and leave it there...

Tudor "Ted" Jelescu
Senior VFX Artist


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Sean MortonRe: Green Screen / Camera Tracker / Plates Question
by on Oct 11, 2011 at 4:26:37 pm

You are correct. I parented it and it just didn't do anything.
My desire was to make it look like the actor was in the virtual space
he was in. Camera Tracker gave me that effect when it added
the camera movement. If it had worked,, the background would have
just rotated round the fulcrum of the actor which would have been
weird.

Thanks
Sean


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Walter SoykaRe: Green Screen / Camera Tracker / Plates Question
by on Oct 11, 2011 at 5:35:16 pm

[Sean Morton] "Camera Tracker gave me that effect when it added the camera movement. If it had worked,, the background would have just rotated round the fulcrum of the actor which would have been weird."

Your background plate should not be a 3D layer.

Tracking gives you 3D data about the camera move in your original footage -- you do not want to re-apply that data (which already exists in the shot itself) to the footage.

You do want to use that data with other 2.5D/3D objects to integrate them into the scene.

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
Creative Cow Forum Host: Live & Stage Events


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Sean MortonRe: Green Screen / Camera Tracker / Plates Question
by on Oct 11, 2011 at 5:45:43 pm

How then would i put my keyed out object into a 3D room then?? If i
rotated around the object enough to see the side wall?? I understand
the only way would be to make the background plate 3d.


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Tudor "Ted" JelescuRe: Green Screen / Camera Tracker / Plates Question
by on Oct 11, 2011 at 7:12:06 pm

Yes, you need a 3d background built in AE. You can either use flat planes set in 3d space to build a box (or a multi faceted object) or import a 3d model using Zaxwerks Invigorator Pro, or use a 3d displacement & Extrusion Plugin like FreeForm Pro to build a 3d background. You get the 3d cam data to replicate that to your AE cam, use the actor shot on chroma as a 2d layer and add a 3d/2.5d environment in AE.

Tudor "Ted" Jelescu
Senior VFX Artist


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Walter SoykaRe: Green Screen / Camera Tracker / Plates Question
by on Oct 11, 2011 at 7:19:37 pm

Sorry my initial response wasn't clearer.

You have an actor on a green screen, and there's a 3D camera move in this shot. You have used CAMERA TRACKER with this shot, first tracking, then solving, then creating the 3D scene. You've also keyed out the green background.

You can create nulls from the tracking points in CAMERA TRACKER to help you position things in space or stick to other visual elements in the original footage. For anything that remains static in the scene, you can simply place the element in AE's 3D space, then AE's camera (created by CAMERA TRACKER with the solved camera data) will take care of the rest.

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
Creative Cow Forum Host: Live & Stage Events


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Roland R. KahlenbergRe: Green Screen / Camera Tracker / Plates Question
by on Oct 12, 2011 at 5:23:23 am

First off, check on your paragraphing and line-ends. Phew!

Then, what you describe, based on how you type, one would be inclined to believe, would be rather 'meh'. I suggest that you post a video of your shot so that folks can have a better position to assist you.

And, if you Parent a 3D layer to the Camera then that layer will pretty much lock into the camera's movement's, hence you won't get any movement of the layer.

Barring all the dodgy stuff and if I take your general question to be whether you should parent to a Null created via one of the points within the point cloud created by Camera Tracker, then my answer is a BIG NO - most of the time.

Upon completion of a solve, you should notice that your camera is parented to a Null BUT all the relevant keyframes exist within the Camera's transforms. That 'Camera Null' is there to allow you to transform the entire Camera move AND to be parented or linked via Expressions to another camera move, from another camera - generally it's painful stuff that is seldom required for 99% of 3D tracking jobs.

What I normally do when I add an object into a solved scene is to first remove the parenting from the Null or Solid that is created from the point cloud. I then copy its transforms onto my 'insert object'. This allows me to move my 'insert object' while having a precise understanding of its transform properties.

Take note that child layers' transform properties do not exhibit their absolute values. Instead, a child layers' transform values are relative to its parent. Thus, in knowing where a layer resides in 3 space, its un-parented values provide distinct and absolute values.

In 2D and 3D spaces, reference points provide us with reference data from which to place other layers, relative to the referenced layer.

To make a long story short, don't bother too much about the parenting that is done in most of the tutorials that you see. They are only useful for placing an object into the scene. For placing more than one object relative to one that is already within the scene or having a better idea of the transforms required post-insertion, then an un-parented layer provides for much more intuitive data from which to work with.

HTH
RoRK

Intensive AE & Mocha Training in Singapore and Malaysia.


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