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victo160

Trackers not following background sequence

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 Hi! I tracked some footage in PF Track, and everything seemed good. My test geo didn't slip or slide around. I exported it as Houdini Script. Brought it into Houdini, trackers all showed up along with the camera. But when I put the image sequence into the Camera background everything is sliding. The trackers don't match up with the background. I don't think my track was as way off as it seems with the background plate. Is there another reason why background sequence and trackers wouldn't be matching up? Any information is great! Thanks!


 

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Many possible reasons...

 

Could be any number of the following:

frame-rate differences

pixel aspect differences

focal length not coming in correctly

image sequence misaligned or not displaying in the correct pixel aspect

Something messed up with the translation order of the camera

 

Check all of these between the import and the PF Track files. Something must be different somewhere.

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Also try simple stuff- check that the camera's resolution is corrrect on the camera node. Does it match your PF track file and your image sequece? Also check to see if your Image sequence is properly filling the frame, and not being stretched.

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There is also the concept of the 'undistorted' plate. Which is how you should be working inside a 3D package. Many cameras introduce lens distortion into recorded footage. Most tracking software offers the option to correct lens distortion and output a new image sequence with undistorted images. You then use those undistorted images in your 3D package as your background. When you render out your finals without the background you will have to re-distort those 3D images to match the original plate, typically done in the compositor.

Edited by Atom

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However, even if you did not 'undistort' your plate in PFTrack, your trackers will still appear to follow the backplate in Houdini, at least. (The problem will show up when you render)

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