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PostPosted: Thu Apr 21, 2016 10:23 am 

Joined: Wed Jul 08, 2015 10:42 am
Posts: 12
Hello!

I have a number of different sensors, but each of them 'see' me differently (in the main, my height):
1) ASUS Xtion Pro #1 - 182cm.
2) ASUS Xtion Pro #2 - 162cm.
3) Kinect XBOX360 #1 - 182cm.
4) Kinect XBOX360 #2 - 176cm.
5) Kinect XBOX360 #3 - 182cm (but i can't use it).

It is clear that they 'see' me differently. So... anyone encountered with this problem? Or the problem is in my hardware? It is unpleasantly when with 5 sensors, I can't connect even 3 of them together, because due to the different height (and other settings) - the quality of tracking is getting worse.

I will be grateful for any advice.


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PostPosted: Thu Apr 21, 2016 3:44 pm 

Joined: Mon Aug 03, 2009 1:34 pm
Posts: 2229
Location: Los Angeles
That's sounds odd. Hopefully somebody from iPi Soft will pop in to respond soon but for now, here are some thoughts:

1. I might be wrong about this but I don't think you can mix Xtion sensors with Kinect. At least, I don't believe it's recommended.

2. What happens when you use only the three XBox Kinect sensors?

3. Could the calibration be off? I can see how that might happen with mixed sensors; how is calibration with just the three Kinect sensors or just the two Xtion sensors?

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PostPosted: Fri Apr 22, 2016 12:35 am 

Joined: Wed Jul 08, 2015 10:42 am
Posts: 12
At first, thanks for the reply. ;)

1. Xtion and Kinect are the same (so they can be mix). At least, as stated in the wiki and forum... and my tests.

2-3. With only three XBox Kinect sensors or with only two Xtion sensors quality is bad, because, again, they see a different height. For Xtion sensors it's really bad (more than 20cm of difference), so i removed one of them. With 3 Kinect sensors difference is not that big in them, but the depth error in the 10-16 centimeters with one of them sometimes spoils the whole bunch of 3 sensors.

PS: errors only in the "scale" of depth, with video it's all right (i hope..).


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PostPosted: Fri Apr 22, 2016 4:23 am 
iPi Soft

Joined: Wed Jan 11, 2012 6:12 am
Posts: 1934
Location: Moscow, Russia
First, how do you get the values of height for different sensors? Is this the value you select for actor height to match an model in Mocap Studio to the point cloud?
If so, did you do measurements in the same actor's pose and sensor position for all sensors?

Depth data produced by sensors has intrinsic distortions. Kinect v2 applies some corrections to compensate this internally, but not Kinect v1 and other sesnsors based on PrimeSense technology. Besides, sensor position may affect depth data, as well as accuracy of detected floor.

I would not pay too much attention to difference in numbers. When using a single sesnor, this does not matter at all - just choose the most appropriate height to match the model and the point cloud. For accuracy of multiple sensors tracking, the main thing is how well point clouds combine with each other. This is determined by the quality of calibration for the most part.


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PostPosted: Fri Apr 22, 2016 8:01 am 

Joined: Wed Jul 08, 2015 10:42 am
Posts: 12
Yes, I understand that with single Kinect height doesn't matter. The problem arises with 2-3 sensors. In the first post I wrote a height, which each sensors "see" in work with other sensors.

I tried different positions and angles for the sensors, but they all give the same height of actor as in the other tests. Point clouds from different sensors almost identical horizontally, but vertically they have a different scale (consequently, different height of actor model, which spoils the quality). And height errors identical for a set of three sensors and two sensors (except those in which height is same).

I think the problem may be due to incorrect detection of floor - with 2-3 sensors one of the problematic point cloud is above or below the "plane of the floor". And the size of the error is almost constant (even with different positions/angles).

Maybe I can try something else? Can you anything advise?
And thank you for your answers. ;)


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PostPosted: Sat Jul 29, 2017 7:53 am 

Joined: Fri Jul 28, 2017 12:43 pm
Posts: 4
I have the same problem.
On one sensor, the height is 182 (correct), on the other 220 (not correct).
I do not know what to do...
Both sensors are identical, the first version of Kinekt.


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PostPosted: Sun Jul 30, 2017 2:09 pm 

Joined: Mon Aug 03, 2009 1:34 pm
Posts: 2229
Location: Los Angeles
What's the surface quality of the floor? If it's super shiny or reflective, you might get inaccurate readings. If that's the case, throw a carpet over the floor.

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PostPosted: Sun Aug 13, 2017 1:55 pm 

Joined: Fri Jul 28, 2017 12:43 pm
Posts: 4
Ordinary boards (pine) without a covering. Often slightly dusted. There is no glare.
Something just did not try, corners, different rooms, higher or lower. There is always a difference in growth of 30 centimeters. This is a very big difference.


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