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Calibration problems
https://forum.ipisoft.com/viewtopic.php?f=2&t=8937		 Page 1 of 1
Author:  Pendtoni [ Tue Jan 14, 2014 4:09 pm ]
Post subject:  Calibration problems
Hi guys, so I'm new to ipisoft and tried to learn calibration today. Hit big problems though.

Basically the setup is 4 ps eye cameras in the square formation.

Camera Heights:
Camera 1 = 1.5 meters
Camera 2 = 1.3 meters
Camera 3 = 1.37 meters
Camera 4 = 1.2 meters

Distance between Cameras:
Cameras 1 and 2 = 7 meters
Cameras 2 and 4 = 5.9 meters
Cameras 4 and 3 = 7 meters
Cameras 3 and 1 = 3.9 meters

A MagLite was used and the 'Cage' method of calibration used to mark out the capture area.

The problems can be seen in the pictures below.

View from camera 1
Image

View from camera 2
Image

View from camera 3
Image

View from camera 4
Image


As you can see a lot of red has appeared. Though the MagLite was mostly visible on all the cameras and it was attached to a pole to avoid occlusion.
In ipisoft mocap after the calibration process took place the cameras in the software, despite unchecking the auto detect initial camera position, the camera heights are all incorrect and some have end up tilted in the viewports.

Not sure what to do. Any tips are welcome.
Cheers!
Author:  vmaslov [ Wed Jan 15, 2014 3:36 am ]
Post subject:  Re: Calibration problems
Hi

What is the "marker misdetection" values in your calibration? You can find tem on the "Scene" tab. Cycle through cameras to get individual value for each of them. It seems that the values are high, much above 10%. This may mean that in reality the occlusion of a marker is much than you assume, despite using a pole.
You can try to find smaller interval of frames for calibration, where the marker is well detected by all the cameras. Set the ROI to this interval and run the calibration again. Several hundreds of frames are pretty enough. See this post as an example of such approach.
BTW, we recommend to record calibration video of about 1 minute length. More frames will barely provide additional accuracy, but increase processing time.

If you wish, you can upload your calibration video to file-sharing service. This would allow me to provide you more specific tips.
Author:  pendtoni93 [ Wed Jan 15, 2014 8:18 am ]
Post subject:  Re: Calibration problems
Tried another calibration test. This time the calibration came through ok.

HOWEVER.

The software got Camera 1 and 2 heights correct or close to it. 3 and 4 are well off. Including the distance between cameras 1 and 2.

I tried manually fixing this. Got it to the correct measures or close to them but the calibrated area is now too high above the floor.

Here's a picture of the incorrect measurements ipi came with

Image

and here is the calibrated area and a small idea of how high it is compared to one camera.

Image

I tried the method you shared before but I couldn't get to grips with it. Tips are welcome as always
Author:  vmaslov [ Wed Jan 15, 2014 12:34 pm ]
Post subject:  Re: Calibration problems
As you disable the "Auto detect initial camera position" feature, have you set approximate camera positions before running the calibration?
Have you marked ground points after the calibration is complete?
While recording a calibration video, do you ensure that all cameras are set to the wide FOV (blue point)?

pendtoni93 wrote:
and here is the calibrated area and a small idea of how high it is compared to one camera.

The image is the same as the previous one.

The calibration video is welcome as always :)
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