Tracking a plane that rotates
by Ian Anderson
on
Oct 30, 2009 at 9:14:58 am
Hey all,
I'm very much a noob to Mocha but i've been really impressed with the first few tracks i've done so far. I'm finding a consistent problem though trying to track a plane that rotates (only roughly 90*). I've uploaded two shots for anyone who might have a minute or two to take a look at here:
http://chillibean.net/~FSEG
They're essentially the same shots, one is a fairly square on shot of an ipod that rotates so the display is landscape as opposed to portrait, the other shot is the same movement but with a phone and angled away from camera.
They're the kind of shots I would've thought Mocha would handle with ease and either side of the rotation I can easily get a pretty stable track. However it's when the object rotates that's when things get funky and surface shape is lost no matter if i track backwards or forwards.
I have tried tracking the thumbs in the shots too as they obscure parts of the objects but it's still the rotation of these things that seems to be thwarting Mocha and myself.
I would be very grateful to anyone who could troubleshoot the shots for me as I may be working on a project where this sort of thing might be a regular occurrence.
Many thanks in advance for your suggestions.
Kindest, ian
Re: Tracking a plane that rotates by John-Paul Smith on Oct 30, 2009 at 1:30:54 pm
Hi Ian,
You need to set the Angle in Search Area. The tracker can handle a bit of rotation without this, but for fast, large rotations like this you need to set it. Just estimate the degrees of rotation per frame and enter it into the field. You should keyframe this value so it's only set for frames where the rotation happens, because searching for rotation slows the tracker down a lot.
Re: Tracking a plane that rotates by Ian Anderson on Oct 30, 2009 at 3:56:48 pm
John-Paul,
Many thanks for your suggestions and quick response! I did find that, as you say, doing a frame by frame track whilst altering the angle property for each frame gave me a much better track. Thank you so much for putting me on the right path!
After getting as close a track as i had got previously I used adjust track to correct where the surface points drifted off.
Thanks again for your help and I'm sure it'll be useful for others to remember that Mocha needs just a little extra help when planes are rotating.
Kindest, ian
Re: Tracking a plane that rotates by John-Paul Smith on Oct 30, 2009 at 4:56:28 pm
Hi Ian,
You can tweak that value frame by frame, but I would just set it to a sufficiently large number at the beginning of the rotation and then back to zero at the end. it just needs to be large enough to include the largest rotation in the sequence.
