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After effects & 3D project -advice

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rob john
After effects & 3D project -advice
on Aug 7, 2010 at 10:36:41 pm

Hey there everyone, I'm planning a short visual effects piece that I will composite in AE & as I'm probably just slightly above beginner level, would like to get some advice before I begin.
One of the main elements of the piece involves putting a walking actor into a CG world & I plan to do this by shooting the actor against a greenscreen (on a chroma green treadmill) and once keyed place them in a 3D environment created in Autodesk Maya.
I am unsure about the best way to execute this so wondered if anyone has any ideas on the best way to get good results? e.g.
1)Should I avoid shooting the actors feet, as I've heard it would be difficult to make them interact in a believable way;
2)Would creating the illusion of walking in the CG world involve keyframing a camera in my 3D world to move at the same speed as the actor on the treadmill?
3)In a few shots I intend to integrate the two worlds with some basic matchmoving but wondered if there are any tips to make the non-matchmoved shots where the camera is static, less sterile i.e. camera moves in post?

I also wondered about the steps involved in getting a good key of the actor and integrating them well into the scene and finally are there any tips & tricks for little things that boost the quality?
Thanks


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Tudor "Ted" Jelescu
Re: After effects & 3D project -advice
on Aug 8, 2010 at 11:15:04 am

I'm sure you can find plenty of tutorials about keying here on the Cow and elsewhere- so I will not go into that.
Matching the light when shooting with the light in the 3d world is a must.
Unless you are shooting on RED or similar, 2k and above, you may want to put the camera sideways and shoot the actor as big as possible in the frame- this way you get more information.
Shoot the legs too- you can always reposition later.
Have tracking marks on the treadmill to match the speed ( black tape + in front of the actor)
If you plan for camera moves- have tracking marks on the screen behind the actor as well. You will need Boujou or Syntheyes to track the 3d camera move and export that to Maya.

When compositing don't forget to lightwrap the actor.
That's all I can think for now- i'm sure you'll get some more advice from the folks over here.

Tudor "Ted" Jelescu
Senior Compositor/VFX Artist
Bucharest, Romania


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Steve Roberts
Re: After effects & 3D project -advice
on Aug 8, 2010 at 12:56:17 pm

Here are my thoughts:

- write down all data: height of lens, angle of tilt, focal length (in a 35mm sense), distance from lens to subject, height of subject, height of treadmill surface. Note that the camera is on the ground, but the subject is on the treadmill -- account for the two different "floor" heights.
- add tracking markers to the treadmill to gauge the speed of the 3D ground as it passes beneath his feet. Measure the spacing of those markers, width, depth.
- yes, shoot the feet, but you might need to crop them if you can't make the shadow, but if you can fake one, it will help sell the effect. Consider a dark 3d floor. Ideally you should have a real shadow in shot.
- in the 3D app, parent the talent object (a plane?) to the camera, or similar
- if you shoot sideways, make sure you're shooting progressive, not interlaced -- if 24p, make sure to remove pulldown in post
- since your scene is static, a matchmover app might not help -- that's why I recommend noting all data in the scene.
- shoot tests!!!!

Anybody else?



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rob john
Re: After effects & 3D project -advice
on Aug 15, 2010 at 11:07:52 am

Apologies for the delay in response, but thanks, there is some great information here, it has opened up new research paths for me!
I like the idea about parenting the talent to a plane, although I only intended to composite the actor with the 3D scene in After effects-Is there some way of extracting the camera data from maya and using it in AE?

Also when you mentioned to: "add tracking markers to the treadmill to gauge the speed of the 3D ground as it passes beneath his feet. Measure the spacing of those markers, width, depth."

I'm unsure exactly how to execute this-How will these markers enable me to determine the speed and how would I remove them later, by duplicating the layer & masking?

Many Thanks for your advice


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rob john
Re: After effects & 3D project -advice
on Aug 17, 2010 at 10:40:39 pm

Apologies for the delay in response, but thanks, there is some great information here, it has opened up new research paths for me!
I like the idea about parenting the talent to a plane, although I only intended to composite the actor with the 3D scene in After effects-Is there some way of extracting the camera data from maya and using it in AE?

Also when you mentioned to: "add tracking markers to the treadmill to gauge the speed of the 3D ground as it passes beneath his feet. Measure the spacing of those markers, width, depth."

I'm unsure exactly how to execute this-How will these markers enable me to determine the speed and how would I remove them later, by duplicating the layer & masking?

Many Thanks for your advice


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