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Does anyone know the minimum parallax requirements during filming for successful motion tracking reconstruction?

I know the documentation says you need:

  • at least 8 common tracks on the both of the selected keyframes.
  • noticeable parallax effects between these two keyframes.

However, after many failed attempts at filming a scene using these guidelines, I was wondering if anyone knows enough about parallax to describe the exact requirements more specifically.

One thing I've wondered is is there a requirement of the relationship of the 8 markers to the angles of the camera, or do you just have to have 8 markers somewhere and the key is only the camera angles?

If you say the key is only the camera angles, can you give any more specifics? I've tried:

  • ~45° on the X/Y plane with ~10° arc into Z, but this video failed to reconstruct
  • ~160° on the X/Y plane with a ~20° arc into Z, and this video reconstructed quite well

As a note, on both of these attempts, the Solve Error was ~0.6, even on the one that failed to reconstruct properly.

I was wondering if 180° on the X/Y plane followed by a 90° or 45° arc into Z (as shown below) would always work, or if that's an unnecessary amount of parallax.

So, in order to reduce trial and error, does anyone know the minimum parallax requirements?

Ideally, I'd like to get good enough correct specifics that they can be added to the Motion Tracking page in the Blender manual.

Thanks!

enter image description here

180° arc on the X/Y plane, followed by a 90° arc into Z

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  • $\begingroup$ If you'd like to see the video I mentioned above that failed to reconstruct, it's here: drive.google.com/file/d/0B_yQeQQ8ImENZ3FEMjJ3WDlHejg/… It's possible I just messed up when setting up the motion tracking in Blender, but even if that's the case, it'd still be good to know what counts as noticeable parallax. Note: In this video, I was not trying to set/demarkate any walls in Blender, just the floor. $\endgroup$
    – Thom Blair III
    Feb 22, 2014 at 19:29
  • $\begingroup$ Not sure if this will help, but what I do is turn the video off (so I just see the tracks, with trails off) and see if I can tell how the camera is moving based off of only those points. $\endgroup$
    – Grant Davis
    Nov 20, 2015 at 16:16

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The tracking points are better to be chosen from different dimensions as they are in real world, in order to cover more obvious parallax difference between frames.

For example, it's certainly not recommended to pick them all from a single plane/ground or a single wall. However, if some are from the ground and others are from a wall, it would be the nicer choice for sure.

I'm not going to propose any AD here, but I learned this thing from the official training DVD - Track, Match, Blend!

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  • $\begingroup$ Thank you for the info on tracking point choice, that is indeed very good advice. Unfortunately, I already knew that so I do it when I film a scene for tracking. Still, though, some of my videos fail to reconstruct. I'm hoping to get some specific information on minimum degrees of horizontal and vertical parallax arc. $\endgroup$
    – Thom Blair III
    Feb 22, 2014 at 17:53
  • $\begingroup$ What does AD stand for? I'm very new here & to forums. $\endgroup$
    – Thom Blair III
    Feb 23, 2014 at 6:15
  • $\begingroup$ @ThomBlairIII ad = Advertisement. :} $\endgroup$
    – Leon Cheung
    Feb 23, 2014 at 7:31
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    $\begingroup$ Oh, THAT ad. I was checking urban dictionary thinking it was another texting acronym...so hard to keep up with all the slang these days. :D $\endgroup$
    – Thom Blair III
    Feb 23, 2014 at 15:41
  • $\begingroup$ I couldn't comment on the exact math to a successful track, but looking at your video I can suggest a couple of things: $\endgroup$
    – user1853
    Mar 25, 2014 at 0:30

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