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Denis26660764bmn1
Participant
July 25, 2024
Question

After effects 3D Camera Tracker recognize foreground as background and vice versa.

  • July 25, 2024
  • 1 reply
  • 724 views

Hello everyone,

I have an important scene that I need to track with the 3D Camera Tracker. It works initially, but I have a big problem: After Effects recognizes the background tracking points as the foreground and the foreground tracking points as the background. As a result, all my targets are flipped.

Since I need to further process the data in Blender later, I need accurate 3D points.

I have already tried the "detailed analysis" and clicked through all the other settings directly in the Camera Tracker. The problem remains the same. Can't After Effects be told somehow that a certain point is in front of another point so that it can solve the camera again and correct the error? Is there another way to improve the tracking so that the depth is correct?

 

Unfortunately, in the shot, there was a lot of panning and zooming, but hardly any forward or backward movement, and therefore no parallax.

 

Thank you very much for any input.

 

Best regards

 

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1 reply

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Community Expert
Rick GerardCommunity Expert
Community Expert
July 25, 2024

Panning shots do not have depth information. Adding a zoom also does not generate any depth information because perspective is controlled by camera position, not focal length. If the camera is moving, the perspective and parallax change, allowing calculations to interpolate and generate a camera movement path. I don't know of any software that can produce accurate depth information from a camera pan.

 

You should be able to use the tracking information from a single point to recreate the panning action accurately. If you have two points that stick through a zoom, you may be able to calculate the zoom value, but you'll have to figure out the focal length and distance from objects in the shot by experimentation. 

 

Watch a VFX-filled feature film and look for the panning or zooming shots. You probably will not see any. If there are any, they were probably created with motion control cameras and a lot of planning.

 

If tracking marks appear on the objects (people, cars), they will throw off the depth information from a moving camera, so they need to be deleted to improve accuracy. After Effects does not offer object tracking, but you can get that with third-party effects like Mocha Pro. 

 

Mocha Pro and even Mocha AE have excellent surface tracking tools. It may be a better option to insert your 3D generated objects in panning shots.

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Denis26660764bmn1Author
Participant
July 25, 2024

Thank you for your input. The camera was handheld, so it's not a static pan. In the end, there is some movement in the shot, but probably not enough for After Effects to make the correct calculations. The depth doesn't have to be perfectly accurate; the main thing is that the foreground stays in the foreground and the background stays in the background.

Apparently, After Effects does recognize some depth in the shot because all the tracking markers are consistently on the "right" plane. It's just that they're reversed, with everything in the background being recognized as near and vice versa. There must be some trick to reverse this displacement and solving the camera the other way around...

R
Community Expert
Rick GerardCommunity Expert
Community Expert
July 26, 2024

Delete your tracker camera and all other created layers.

 

Set an origin and ground plane somewhere that makes sense using just the foreground or background tracking targets. Add a solid and camera using the same marker. See if that helps.

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