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Tracking the same action gets different results?
https://forum.ipisoft.com/viewtopic.php?f=2&t=9031		 Page 1 of 1
Author:  garethfann [ Thu May 01, 2014 7:46 am ]
Post subject:  Tracking the same action gets different results?
Hi,
I've been using iPi with 4 PS eyes for just over a week now, and I feel like I'm starting to understand the ins and outs of the software. This morning an action I tracked went really well. I did not have to fix any tracking errors at all. So pleased with the results, I thought that this would be a great opportunity to run some tests and and compare how changing some parameters affects the data. Such as head tracking, shoulders, and the different spine options. I saved my actor and re-opened the video. Re-positioned and refitted the actor and tracked forward in the exact same ROI as before.
It looked terrible. I spent the next hour trying to recreate what I had been able to easily accomplish earlier in the morning.
At one point I went back to my good project file, deleted all the keys in the ROI and tried to track forward again. Still looks terrible and I did not realize that the project saves automatically so I lost that good tracking result.
Any idea as to why I cannot recreate what seemed effortless the one time this morning?
Author:  madmonkfish [ Thu May 01, 2014 7:19 pm ]
Post subject:  Re: Tracking the same action gets different results?
One tip (I use this method) is to save different Project files when you do different tasks - this means you can re-load different versions. The Project will also save your actor settings and (if you've done any post processing) that'll save too - along with teh parameters you've set for trajectory filtering.


I'd suggest starting a clean project. Load your calib/actor files and start from scratch. This way, there's no project cache. Also, so it's easy to manage your data, keep the filename of teh video but add characters (so it's easy to identify).

Then, when you've done a track you're happy with, mark the ROI's and save it. I always save one like this, I add 'xxx_RAW' to it's filename, so I know that it's not been worked on (ie this version does not have post processing applied). I use RAW and POST in caps so I can easily identify the project file, handy when you're scanning through lots of shots :)

I then save another copy, with 'xxx_POST' added to the filename (this is a copy of the same data, but, as it has a different filename it's a different cache/project etc). Now, mess about with this one and apply filtering etc. When you're happy, save this. It'll write over your other version, but that's OK, as you now have a RAW and a POST version.

The advantage with this method is you can always load a pre or post version. Obviously, you can do more work on the file, just make sure that, before you do, you save another version (ie WIP_01) etc as, if you don't do a save before you start, the project file will be updated/changed.

That's probably what happened to your data, the project file has been worked on too much, that's why a fresh start might help (unless you've tried that already?).
Author:  garethfann [ Fri May 02, 2014 4:17 am ]
Post subject:  Re: Tracking the same action gets different results?
Thanks for the reply.
Once I realized that mocap studio will autosave, I started doing something similar. I saved a "raw" file and then saved as for "post". I keep going back to my raw file and it's as I set it up initially (actor with initial pose set and ROI basically), but I still can't get the same result from tracking forward. I've even started completely from scratch, ie. recalibrated, re-shot.
This problem is concerning to me because how will I know for sure if a tracking result repeatable? And all the times I got a bad tracking result and chalked it up to a bad calibration or just not setting up the actor properly could have been something else. I'm positive that this problem has to be something I'm doing but I cannot figure it out.
Author:  vmaslov [ Sat May 03, 2014 12:52 pm ]
Post subject:  Re: Tracking the same action gets different results?
Hi
Tracking should be repeatable if you start it with all the same conditions: the same initial frame, the same initial pose, the same actor params, the same tracking options etc. It's hard to say what went wrong when you've created a new project - accidentally wrong scene, or actor params? But it's indeed very strange you could not complete the tracking in the same project once more.
I might ask you to send the video and project to us for review. However, I'll only be able to check it on May 6 at the earliest time.
Regarding the autosave feature. Though it has a good purpose, we realize that in its current implementation it sometimes stands in the way. We plan to improve it in V3 to prevent an unexpected loss of previously tracked data.
Author:  garethfann [ Mon May 05, 2014 12:52 pm ]
Post subject:  Re: Tracking the same action gets different results?
Thanks! I have not figured out what exactly was happening in those cases, but I moved one of my cameras that was pretty high (2.2m) to a lower position (1.8m). I recorded some a new action and I was able to track that same action multiple times with different parameters. I can't imagine that moving the camera fixed my problem, but if it happens again I'll be sure to send you my files.
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