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Unusual character shake after tracking
http://forum.ipisoft.com/viewtopic.php?f=2&t=585
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Author:  Owain Raymaker [ Sat Sep 12, 2009 3:21 pm ]
Post subject:  Unusual character shake after tracking

Hi all

Although it has been a tough learning curve, I have finally managed to consistently calibrate a Logitech 9000 4 camera set-up and get some decent tracking from it. Many thanks to the informative comments found on the forums :-)

However, even after running a high-rez track on a 30fps 4 camera shoot, with the correct clothing and decent lighting, I am noticing that the character/skeleton is vibrating/shaking a lot - mainly at the arms and hips. Is this normal? I can't see it happening on the ipisoft videos or the Lightdog ones - so am I not analysing the shape correctly or fitting the pose correctly? I must emphasise the point, that the tracking works well; its just that the body seems to vibrate a lot when standing still.

Any help would be greatly appreciated.

Owain :-)

Author:  Michael Nikonov [ Sat Sep 12, 2009 9:32 pm ]
Post subject:  Re: Unusual character shake after tracking

Some jitter (shaking) is expected. You can smooth it using using Trajectory Filtering controls on Tracking tab.

Jitter will possibly be reduced in future versions of iPi Studio. We actively research various smoothing algorithms and will probably come up with something more sophisticated then current Trajectory Filtering.

I would appreciate if you could send me an example animation in BVH format so that I could look at it and maybe do some debugging. You can send just the animation, without original video.

Author:  Owain Raymaker [ Sun Sep 13, 2009 8:45 am ]
Post subject:  Re: Unusual character shake after tracking

Thanks Michael - I'll upload the bvh later on today.

So I use the smooth trajectory button before or after tracking?

On another note : I plan on exporting out to Poser Pro via the default Second Life avatar shape 'default T-Pose.bvh'. I imported one bvh into SL and the results were pretty good for a first time. However, the neck and head got stuck in one direction; the animation inside Poser Pro was fine.

Any ideas guys?

Cheers

Owain

Author:  Michael Nikonov [ Mon Sep 14, 2009 11:43 am ]
Post subject:  Re: Unusual character shake after tracking

You should use "Smooth Trajectory" button after tracking. Using it before tracking has not effect because "Start Tracking" button resets it to a default value.

Current version of our software cannot do head tracking, that's why you see head stuck in one direction. Head tracking is in the works and will be introduced in future versions.

Author:  Groot [ Sat Nov 14, 2009 10:44 am ]
Post subject:  Re: Unusual character shake after tracking

Ah, I just noticed post about "smooth trajectory." Will try it in my next session.

So what does "Sharpen trajectory" do? Does it add more jitter?

Author:  Groot [ Sat Nov 14, 2009 11:33 am ]
Post subject:  Re: Unusual character shake after tracking

Hmm, I tried Smooth, and I'm not sure I did it right. How many times do I push the button? Do I push it at various intervals, e.g. every 30 frames? Does the "strobe" button affect it at all?

Author:  Michael Nikonov [ Sun Nov 15, 2009 6:56 am ]
Post subject:  Re: Unusual character shake after tracking

"Smooth Trajectory" applies filtering to entire Region of Interest on timeline.

You can push the "Smooth Trajectory" many times to increase its effect. It displays the number of filtering passes (see the label between "Sharpen" and "Smooth" buttons). Typically, you would want to leave it at default ("2") for fast/large motions like dancing or martial arts. You may need to increase it to "5" or "10" when character is standing in place (that's when jitter is usually visible).

All "Sharpen" does is undo the effect of "Smooth".

Author:  Groot [ Sun Nov 15, 2009 7:44 pm ]
Post subject:  Re: Unusual character shake after tracking

Thanks!

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