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 Post subject: Calibration Impossible
PostPosted: Mon May 24, 2010 9:20 am 

Joined: Fri Apr 10, 2009 6:27 am
Posts: 35
Location: france
I have a lot of question about the calibration because we failed to calibrate since a long time.
But i'm french so i will try to write it correctly and my english is awfull.

First i want to know what is the most important between the frame rate or the résolution ?

here there is my calibration video

http://dl.free.fr/r6hV9fEHS

and the capture

http://dl.free.fr/rmr7EY27p

we use 4 SPC 1030NC webcam (79 FOV)

If someone can give me a calibration video with a captured video, i will try to see if i can calibrate the system.

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PostPosted: Mon May 24, 2010 12:30 pm 
iPi Soft

Joined: Tue Mar 31, 2009 9:13 pm
Posts: 804
Hi,

I downloaded your calibration video. It has the following problems:

1) The video is too dark. You should not turn off the light completely when doing calibration. It is very hard to see what is going on when all you can see is the marker.

Try reducing camera exposure during calibration, instead of turning off the light. See our tutorial video for example: http://www.ipisoft.com/animation/tutorial-src.zip

2) According to Philips, your camera FOV is 80 degrees, not 79: http://www.consumer.philips.com/c/webca ... ifications

3) In your video, marker is not visible (obscured) in camera #3 from time to time, as the result you have too many bad (red) points.

4) You are moving the marker too quickly. Try moving it slower, this will reduce motion blur.

5) You posted links to 2 videos. Both of them represent the same video file (calibration). As far as I understand from your post, the second video was supposed to be capture video, not calibration video.


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PostPosted: Mon May 24, 2010 11:33 pm 

Joined: Fri Apr 10, 2009 6:27 am
Posts: 35
Location: france
Sorry about the second link, this should work better

http://dl.free.fr/cNWHl15eJ

when you said the video is too dark, I thought it would work better in the absolute dark with just the marker.

I wonder if i can calibration the scene by editing the .xml save with DMC, because we can give cameras exact position, anyone try this ?

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PostPosted: Tue May 25, 2010 6:06 am 
iPi Soft

Joined: Tue Mar 31, 2009 9:13 pm
Posts: 804
apside wrote:
when you said the video is too dark, I thought it would work better in the absolute dark with just the marker.


Our marker detection algorithm should work fine in fully lit scene.

Our tutorial calibration video looks dim because we turned down camera exposure during calibration, to reduce motion blur.

To summarize:

Do not turn off the light. Just turn down your camera exposure during calibration. You should have no problems doing it - your Philips camera has exposure control.

Do not move the marker too quickly. This will help reduce motion blur.

Use 80 degrees FOV setting for your Philips SPC 1030NC cameras.

apside wrote:
I wonder if i can calibration the scene by editing the .xml save with DMC, because we can give cameras exact position, anyone try this ?


No, you cannot manually set all camera system configuration parameters (positions and orientations). This is not possible.

We processed your video files, here are the results:

http://www.ipisoft.com/downloads/video/ ... tion.mocap
http://www.ipisoft.com/downloads/video/ ... .scene.xml
http://www.ipisoft.com/downloads/video/ ... tion.mocap
http://www.ipisoft.com/downloads/video/ ... lation.bvh
http://www.ipisoft.com/downloads/video/ ... _biped.bvh

Your calibration video contains too much motion blur and marker is obscured in 3rd and 4th camera.
As the result, it is hard to calibrate and it is impossible to see where the ground is.

Because ground plane is not defined, feet movement cannot be tracked, so the animation looks a bit unnatural.

You need better calibration video.

In addition to this, it is strongly recommended that you use more light and do not use white T-shirt. Your video is too dark, use more light sources. White T-shirt is not a good choice, because shadows are very visible on white. For your environment (black background), we recommend a primary color (red, green or blue) for T-shirt. A good choice would be green T-shirt and blue jeans.


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PostPosted: Tue May 25, 2010 6:16 am 

Joined: Fri Apr 10, 2009 6:27 am
Posts: 35
Location: france
OK
After your reply, I' have tested another configuration (only 3cams) and another way to calibrate (much more slowly and work with exposure) and the results are MUCH MUCH better...thanks a lot.

Anyway, i will try another calibration to be sure that is not a lucky strike...

Work in Progress i will tell you if i can reproduce the same quality.

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PostPosted: Tue May 25, 2010 12:08 pm 

Joined: Mon Aug 03, 2009 1:34 pm
Posts: 2269
Location: Los Angeles
Michael Nikonov wrote:
Do not turn off the light. Just turn down your camera exposure during calibration. You should have no problems doing it - your Philips camera has exposure control.


Ah, this is good to know. It's been a few months since I did my last iPi session, but I was having trouble calibrating it. I thought it might have been the particular version of iPi I was using because I had better results with previous sessions, but now that you mentioned this, I recall that I did turn off most of the lights in the room for this calibration session. (I had assumed this would improve 'visibility' of the maglite.)

Thanks for the info Michael. I'm finally catching up on my other work, and this info (plus the PSP cams and new software,) makes me want to do a new test as soon as possible. :)

Greenlaw

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PostPosted: Thu May 27, 2010 9:43 am 

Joined: Fri Apr 10, 2009 6:27 am
Posts: 35
Location: france
All right, now the calibration work perfectly, thanks for your help.

I have some another important questions:

-actually, shoulders are not independent of the pelvis,is it planned
to be corrected ?

- is it important to have 1 cam up above the others like in your tutorial?

-what is the best way to place 4 cam (all in front or square, to have an opposite angle ?)

-wearing gloves can help the system ?

-What is the best: running the entire region of interest before "arms or legs corrections"
OR we have to stay front of the screen and put the pause tracking and adjuste the pose ?

-ground shadows are problematic or not, I mean its better to have a bright scene, with ground shadows, or it's better within ground shadows ?

Anyway, thanks a lot for your patience in this forum.

PS: Is there anothers frenchies who use your software ?I would like to create a "French section in your "GENERAL TOPICS"

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PostPosted: Thu May 27, 2010 11:09 am 

Joined: Fri Apr 10, 2009 6:27 am
Posts: 35
Location: france
Quote:


We processed your video files, here are the results:

http://www.ipisoft.com/downloads/video/ ... tion.mocap
http://www.ipisoft.com/downloads/video/ ... .scene.xml
http://www.ipisoft.com/downloads/video/ ... tion.mocap
http://www.ipisoft.com/downloads/video/ ... lation.bvh
http://www.ipisoft.com/downloads/video/ ... _biped.bvh
[/quote]

impressive how did you succeed this?

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PostPosted: Thu May 27, 2010 11:38 am 

Joined: Mon Aug 03, 2009 1:34 pm
Posts: 2269
Location: Los Angeles
apside wrote:
- is it important to have 1 cam up above the others like in your tutorial?

-what is the best way to place 4 cam (all in front or square, to have an opposite angle ?)

-wearing gloves can help the system ?

-What is the best: running the entire region of interest before "arms or legs corrections"
OR we have to stay front of the screen and put the pause tracking and adjuste the pose ?

-ground shadows are problematic or not, I mean its better to have a bright scene, with ground shadows, or it's better within ground shadows ?

Anyway, thanks a lot for your patience in this forum.

PS: Is there anothers frenchies who use your software ?I would like to create a "French section in your "GENERAL TOPICS"
Hi,

FWIW, here's what I've found based on my own experience with iPi DMC and what I've read elsewhere in these forums.

- Camera Height. Having a camera higher up helps as it gives the system more spatial information to work from. Just don't put all of the cameras up high; I tried this early on and it can make some things better and some things worse. Basically, I place the cameras at various heights above and below eye level. Don't forget to write down the heights of each camera.

- Camera Positions. I've do my setups generally in a 'square' configuration, but not exactly square. I think I read that the cameras should not be directly facing each other, though I'm not exactly sure why. My guess is that some variance in position and angles makes it easier for the system to calibrate camera positions and track data. To be honest, I might be making this up as I don't know where I got this info. :)

- Gloves. All you need is contrast between your hands and clothing, but I read that in the current software gloves don't really make much difference for accuracy. FYI, wearing two different colored gloves absolutely do not help, though some of us wondered if an option to distinguish left and right hands and feet by different glove and sock colors could be added in a future version.

- Ground shadows. Generally speaking, I don't think this is a problem unless the shadows are as dark as your pants and if they cross each other in a camera view. What's more of an issue, in my experience, are floor reflections. I did a test in an environment with a very shiny floor, and seeing the second maglite in the floor affected calibration, and seeing a mirror image of the actor also hurt tracking. To correct this, I had to stamp a clean plate of the floor for all four video streams, which is obviously not an ideal situation.

Hope this helps. At least until official info from Michael is posted. :)

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Artist/Partner - Little Green Dog | Demo Reel (2017) | Demo Reel (2015) | Demo Reel (2013)

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Last edited by Greenlaw on Thu May 27, 2010 12:31 pm, edited 1 time in total.

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PostPosted: Thu May 27, 2010 11:52 am 

Joined: Fri Apr 10, 2009 6:27 am
Posts: 35
Location: france
It's help and thanks for those details.

What about the corrections during the "capture" ? I mean best results are better without intervention during the process and the corrections should be done after, so a second pass should be done another time.

Or it's much better controling the capture, and when there is an error, about leg or arm, you make a pause, correct it, and relaunch the capture ?

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