Mocha Tracking Problem

inScapeDigitalinScapeDigital Website User Posts: 715 Just Starting Out
Hi guys,
I'm just trying to do a simple 3D track of a desk that I filmed. In Mocha I was able to track it easily and you can see in the video the splines are locked on very well. However, when I import the Comp Shot into HitFilm, the points 'bounce' all over, even though they're general orientation matches the movement of the shot. Also when I Solved the Camera it was 93% accurate.
This could totally be my fault, just wondering if anybody has a fix? Thanks.
Video on Google Drive: https://drive.google.com/file/d/0BxpZgx1QsJPaWU1PWEJta1VTRU0/edit?usp=sharing

Comments

  • NullUnitNullUnit Website User Posts: 791 Just Starting Out
    I've had this problem too. Mocha is still kind of a mystery to me because of it. It seems like you do everything correctly, but the track is still dodgy. I hear about people having breakthroughs where they suddenly "get it" and can use mocha just fine, but I haven't had that breakthrough yet. 
  • AxelWilkinsonAxelWilkinson Staff Administrator, Imerge Beta Tester, HitFilm Beta Tester Posts: 5,243 Staff
    You cannot check a track with the splines.  This is crucial, so I will repeat it.  The splines have 0% to do with checking the accuracy of the track.  To check the accuracy, you need to set up the surface and grid.  Setting up your surfaces relatively small will help improve the accuracy over large surfaces.  Keep the splines as big as possible, to track lots of texture, but use small surfaces.
    What type of movement are you tracking?
  • inScapeDigitalinScapeDigital Website User Posts: 715 Just Starting Out
    The shot is of a flat desk where I just walk around it slightly, a small parallax.
    By surface do you mean the blue planar outline and the pink grid? If so, I did that after I created the splines.
  • Triem23Triem23 Moderator Moderator, Website User, Ambassador, Imerge Beta Tester, HitFilm Beta Tester Posts: 18,307 Ambassador
    Actually, when I watched your video I thought I could see drift on the splines in mocha. I'd like to see the mocha track with the splines and grid on in mocha.
    Mocha's a tricky beast. Sometimes, just moving a spline point and resolving will fix a strange track. Also, what was your pixel percentage when tracking the layers? default 50%, or did you go to 90%.
    Have you played around with/learned the "Adjust Track" settings in mocha? That module is, basically, a simple 4-point track that can fix with drift. Basically, you pick a frame, move the tracking markers to points, find the point of farthest drift, then readjust the tracking points. Here's a quick Mary Poplin tutorial--she's not doing a camera solve, but the Adjust Track principles and execution remain the same.
    To expand on what Axel said about large track splines and small surfaces--Remember that Mocha in interpolating physical data from a pixel matrix--a hard series of squares. A large surface give mocha more pixel data to extrapolate from, and a small surface.... Well, if you have a smaller surface, mocha can use all the extra pixel from the large spline to calculate finer motion--if you have a larger surface, mocha doesn't have as much "resolution" to generate motion vectors. I think, for example, you could expand the shape on the surface of the desk--wrap it around a bit more to the sides, and around the stuff sitting on the desk. That whole desktop is a single plane, so track as much of it as you can. From the video, it looked like your surface 9based on your points) was almost the same size as your spline. Enlarge the spline, shrink the surface and I bet that'll clean up the track. :-)
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