3D camera tracker creates enormous 3D space

[martinl17124940]

Hi there,

I got some greenscreen footage with a mobile camera and am supposed to key and track it.

There are quite a lot of tracking marker both in the front as well as on the back of the greenscreen.

When I use the 3D camera tracker and after analysis e.g. create a text + camera, The camera has a movement of about 10000px, where it moved like maybe 3 meters and the text that I pinned to the background is around 100000px away, where it have been around 5-10 meters on the set.

If I understand it right I would need to put my 3D set (a very simple one, I created in AE) to the same Z of 100000px. That's quite unconvenient.

How can I fix that scaling?

Thanks a lot for your help!

Martin

[Mylenium]

How can I fix that scaling?

Not really. Unfortunately the AE tracker can't be calibrated and nay solution it calculates is arbitrary and bears no relation to any realworld measurements. Sometimes the resulting scene is too big, sometimes too small, sometimes just right. Of course you can multiply the keyframe values by applying an expression like value*0.1 or similar, but you still have to put up with figuring out the correct camera settings to compensate for the scaling, which actually is the tricky part.

Mylenium

[Roei Tzoref · Accepted solution]

Try this:

1. Add a 3d null

2. Parent the camera to the null

3. Scale the null to your liking. Maybe 0.1%

4. Delete the null

[martinl17124940]

Thank you both for your helpful answers.

Scaling the camera with a Null did the trick.

[Rick Gerard]

I would go about this project a little differently. First, remove any lens distortion - the most likely cause of huge 3D spaces. Second, make sure you set an origin and ground plane. Third, create two or three 3D solids in key locations and check for accuracy. I haven't seen the shot but every time I end up with a huge 3D space created and followed these steps things were more accurate and the track was better. AE's calculated camera has Zero lens distortion so unless you are shooting with really good glass on a pro camera you're probably running into this problem and the edges are going to have a hard time staying stuck to the video. GO Pro Studio has an excellent distortion correction tool available. For my feature film work I try and always get some test footage from the lenses or look up a distortion profile for them before doing any serious compositing that has to extent to the edges of the frame.