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PostPosted: Sun Nov 06, 2016 12:05 am 

Joined: Mon Aug 03, 2009 1:34 pm
Posts: 2423
Location: Los Angeles
Just curious: in Statistics, what does Background Area signify? Is this value the area of the room that was 'readable' by the depth sensor? That is, the total of 'non-yellow' area?

I'm typically getting about 75% to 78% with each Kinect One (v2) when recording at night. Is this a normal reading? If that's the good area vs. bad aread coverage, I'm guessing this is fine because nearly all the 'bad' area is far across the room and well outside the performing space.

I did notice that one of the Kinects seems to be getting 'yellow' on the floor apparently coming from the other Kinect across the room. Maybe IR interference? Is this something to be concerned about and should I be careful to avoid? The sensors are not really pointed at each other--maybe 170 degrees or less even--so I was surprised to see this. (I'll try adjusting angles to improve this.)

One really weird question: Occasionally, I see a ball shaped 'floater' rising up or floating down in the depth sensor preview. At first I thought maybe it was an insect but I haven't seen anything flying or floating in the room, and nothing appears in the RGB channel when I have both views open. It's not there all the time and I've seen it before in previous sessions, in day and night time. It's kinda spooky but I'm sure there must be a logical explanation. Any ideas?

Maybe I'm just watching too many spooky movies. :)

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PostPosted: Sun Nov 06, 2016 12:09 am 

Joined: Mon Aug 03, 2009 1:34 pm
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Yeah, I'm definitely getting IR from the other Kinect too. I'm not concerned about the 'yellow pulsing' at the sensor but it's being reflected on the floor at the other end of the room too.

I'm going to try angling one sensor away a few more degrees to see if this clears the problem.

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PostPosted: Sun Nov 06, 2016 12:13 am 

Joined: Mon Aug 03, 2009 1:34 pm
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Angling one sensor a few more degrees did minimize the IR interference issue. I can still see occasional 'flashes' from the other sensor on the floor but the Background Evaluation looks very clean so maybe this isn't a problem.

I'm not really concerned about this, just thought to mention it.

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PostPosted: Sun Nov 06, 2016 12:43 am 

Joined: Mon Aug 03, 2009 1:34 pm
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Location: Los Angeles
I shouldn't complain; the calibration results have been perfect this evening.

As a matter of fact, better than I've ever seen it before. :D

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PostPosted: Sun Nov 06, 2016 12:45 am 
iPi Soft

Joined: Wed Jan 11, 2012 6:12 am
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Location: Moscow, Russia
Background area value in statistics shows how much of the picture is considered as background (based on previously evaluated background). Low values (below 30-50%) usually indicate that there are significant changes in the scene and background should be re-evaluated.

Quote:
One really weird question: Occasionally, I see a ball shaped 'floater' rising up or floating down in the depth sensor preview.

Phew! I was afraid that it was only me who sees those weird things. Now I'm not alone :)
I suppose those are specks of dust floating somewhere near to IR emitter or receiver on rear occasions.


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PostPosted: Sun Nov 06, 2016 2:53 am 

Joined: Mon Aug 03, 2009 1:34 pm
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Location: Los Angeles
vmaslov wrote:
Background area value in statistics shows how much of the picture is considered as background (based on previously evaluated background). Low values (below 30-50%) usually indicate that there are significant changes in the scene and background should be re-evaluated.

Ah! Thank you. That makes perfect sense to me now.

Quote:
Phew! I was afraid that it was only me who sees those weird things. Now I'm not alone :)
I suppose those are specks of dust floating somewhere near to IR emitter or receiver on rear occasions.

Thanks for confirming my suspicion. Every time I approached the master computer, I'd see those 'floaters' on the screen for the nearest sensor, but then they'd disappear as soon as I pressed Record. That made me a little paranoid at first but then I figured I was probably stirring up a little dust whenever I passed the sensor coming into the computer room. :D

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PostPosted: Sun Nov 06, 2016 8:42 am 

Joined: Thu Sep 04, 2014 9:47 am
Posts: 897
Location: Florida USA
...

I am wondering if you ever tried using a black mat or rug on the floor? I believe has to be solid black or very very dark color, all I tried was black.

I have tried this with dual Kv2s, and it makes no data return from the covered floor area, (solid yellow), which is fine, it doesn't affect the floor grid setting, or the recorded performer point cloud and allows more of the feet to be detected when on the floor.

I found yellow areas not to be a bad thing with Kinects, it eliminates some of the background point cloud noise in the processing stage and has no effect on the point cloud actor tracking.

I really think you could use black sheets, or some other black material to use as back drops from behind the sensors to meet at the edges of the sensors view capture volume and make the whole scene yellow and it would still detect only the performer once they entered the scene and would delete most of the background noise.

I will try a demo with the Kv1 and see for myself using this theory, if it does then should do the same with Kv2, I already know it worked for the floor with Kv2.

...


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PostPosted: Sun Nov 06, 2016 10:30 am 

Joined: Thu Sep 04, 2014 9:47 am
Posts: 897
Location: Florida USA
...

Just tested it quickly with 1 Kinect 360, wrapped the capture view area in front of the sensor with the weed block material I use for shade and worked fine, it removes any colored depth info from the background for the most part, only showing yellow and the actor cloud and adjusting actor depth colors while recording and tracking, there may be flashes of purple, or other color depth information completely behind or on sides, but far better than completely colored depth as it is without it.

I used it just now and have sunlight coming in all around behind it, since it isn't thick, or solid material it hangs easily and blocks that sunlight creating a yellow background and I have a thin black canvas type material I laid on the floor about 6 ft x 6 ft area covered, leaving floor outside to be detected as purple for ground grid.

Single Kinect 360 isn't the best test, Dual Kinect One would work much better I am sure with better results.

Just a suggestion that may help someone during daytime Kinect recordings and that black weed block is cheap and surprisingly strong, but you may need a few rolls to cover the needed areas fully, it has a shiny side and a dull side, I used the dull side to sensor, but not sure all brands are made that way.

Dual Kinects you can only get so much floor volume anyway, so can just use whatever black heavier material or carpet to give a full usable feet capture volume, just doing that should improve the feet tracking even more using Kinect One, Kinect 360 still has poor feet tracking ability and a floaty output.

May be useful info., may not, but it does work.

...


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PostPosted: Sun Nov 06, 2016 6:32 pm 

Joined: Mon Aug 03, 2009 1:34 pm
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Location: Los Angeles
Hi Snapz,

Thanks for the comments. That's very interesting, although some of what you wrote contradicts my own experience over the years:
Snapz wrote:
...I am wondering if you ever tried using a black mat or rug on the floor? I believe has to be solid black or very very dark color, all I tried was black.

We happen to have a large brownish patterned rug on our living room floor which has been very useful. I learned a few years ago that when you have a shiny floor, a rug is very effective for knocking out reflection, whether you use PS Eye or Kinect, but for different reasons.

Two things:

1. In my experience, a matte black carpet might be a poor choice because that specific surface tends to absorb the IR light and you want the surface to bounce rays back to the sensor for them to register the depth. At least, that's what I've noticed about matte black for clothing and props. I haven't thought about what it means for the floor--maybe interfere with proper floor detection?

2. The 'reflection' I'm talking about is actually more visible on the rug directly in front of the opposite sensor, and the polished floor outside of the rug. So technically, it's doing exactly what it's supposed to do--the issue is that the near sensor is picking up rays from the opposing sensor--I think this is why it reads as 'yellow'.

Quote:
I have tried this with dual Kv2s, and it makes no data return from the covered floor area, (solid yellow), which is fine, it doesn't affect the floor grid setting, or the recorded performer point cloud and allows more of the feet to be detected when on the floor.

I found yellow areas not to be a bad thing with Kinects, it eliminates some of the background point cloud noise in the processing stage and has no effect on the point cloud actor tracking.

That's very interesting. It sounds like instead of having the software accurately create the ground, you are in effect canceling out the ground scanning altogether. I guess since the orientation of the ground plane can be assumed with just a little bit of data sampled over a large area, maybe that's all you need?

Don't know. Personally, I still think more data would lead to greater accuracy though. For example, even though the 'near' sensor was canceling out IR rays from the far sensor, I still got some of the best calibration and motion recordings last night. I think this is because I still got very clean floor data for most of floor in the the actual performance area. (Although, I should also attribute improved results to the recent Kinect-specific improvements in Mocap Studio.)

Quote:
I will try a demo with the Kv1 and see for myself using this theory, if it does then should do the same with Kv2, I already know it worked for the floor with Kv2.

Yes, multiple Kinect One (v2) sensors do work significantly better than multiple (v1) sensors. The main thing I've noticed in comparison is that the captured data is less noisy with Kinect One (v2) so there is far less 'jitter' in the data to start with. Also, I'm finding Kinect One (v2) works much better in daylight than v1 did--v1 is apparently more susceptible to IR interference from sunlight. (Although the recording last night was obviously done at, well, night.) :)

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PostPosted: Sun Nov 06, 2016 7:05 pm 

Joined: Thu Sep 04, 2014 9:47 am
Posts: 897
Location: Florida USA
...

I didn't use black carpet, or rug, it was a nylon canvas type material, and yes, some floor was visible purple around the edge to let the auto grid figure it out correctly, there was an issue with using one Kinect 360, and when I tested the Kinect One also, that allows the feet not to refit very well to me, they tend to want to fade backwards, I don't know if that has been rectified in the latest updates or not for Kinect One, but it's still an issue for the Kinect 360 I used, but dual sensors it wasn't an issue for either version.

Was just a suggestion, if your getting good feet tracking then no need to do it, but I know it isolates and shows more of the feet when touching the ground is all and I know using solid black back drop that shows solid yellow wall areas doesn't affect the performer cloud, or the tracking in Studio at all, it just removes the purple noise better behind the performer when done right.

My area is open, so this would be more useful to users with furniture and things in the sensors view, so draping those things in black material will cause no data will be returned from them on the recordings.

I wanted to mostly find out if a black backdrop would eliminate the noise behind the performer in the cloud and it did, nothing shows directly behind the performer cloud, nor under the feet when tracking.

I don't use Kinects, so not an issue for me, I just like to see what happens when I try things, my PS Eye setup works great, but for most I do think the Kinect One is more manageable, so just posted the info. if it could help anyone.

Glad you finally got everything up and running the way you like it :)

...


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