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Dumb question - tracking footage, having border smear problems... So, just tracking some of my own footage for the first time and as I'm approaching my first test renders, I've encountered some weirdness with the boarders of the image - smearing in previews, transparency in render. Obviously, this is not my intended result!

The footage is from an iPhone 4, resolution 1280x738 w/display resolution of 1280x720.

I've a horrible feeling I've set my proxies up wrongly - and that I should immediately know what the problem is here... but I cannot remember the solution! Can anybody jog my memory? enter image description here

Maaaan, I'm feeling stupid...

--Rev

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    $\begingroup$ Sounds to me like the sort of weirdness which shouldn't happen at all.. You might want to file a bug report. $\endgroup$
    – gandalf3
    Commented Sep 13, 2015 at 18:13
  • $\begingroup$ Gahh. Worried that it's not a bug, but have submitted a report nonetheless. $\endgroup$
    – Reverend Speed
    Commented Sep 13, 2015 at 19:54
  • $\begingroup$ Guys, any idea what I should be seeing instead of the smearing? Just a blank background grey? @cegaton, as stated the source footage is res 1280x738 w/display resolution of 1280x720 - my project res (Dimensions->Resolution in Properties) is 1280x720. I've tested w/1280x738, but it doesn't seem to affect the smearing. In this case, my project res matches the res of the original video. Unticking 'undistort' 'fixes' the bowing, but undistort is necessary for the track... $\endgroup$
    – Reverend Speed
    Commented Sep 13, 2015 at 20:05

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The smearing on the edges is perfectly normal if you are undistorting. It's most notable when the lens distortion is the pichcushion type. Blender is deforming your image, and it fills the missing parts with the color of the last pixel on that row or column, since there is no other way to reconstruct the information of things outside of the image limits.

Here's an exaggerated example to illustrate the point:

enter image description here

Other programs do give you the option of making the edges transparent or black. Blender does not (As far as I know).

To solve the issue you do have a couple of options:

1- (The lazy and lossy option): Resize the undistorted image in the compositor so that the smearing at the edges doesn't show.

enter image description here

The downside is that you'll loose some information and the image might degrade with the re-scaling.

2- Work with undistorted proxies as a reference to create your 3D scene, but for the final render bring back the original (distorted) video and distort the 3D scene to match the distortion of your lens:

enter image description here

You loose no information and your 3D scene will follow the distortion of your original video.

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  • $\begingroup$ Aha! Lesson learned. Thanks Cegaton! --Rev $\endgroup$
    – Reverend Speed
    Commented Sep 14, 2015 at 17:54
  • $\begingroup$ EDIT: Ultimately, I used a combination of the two techniques - redistorting the comp'd footage at the end of the chain, then scaling slightly to remove tiny slivers of transparency at the edges of the image. Will def use the proxies method mentioned for my next project...! $\endgroup$
    – Reverend Speed
    Commented Sep 14, 2015 at 19:00

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