Calibration frustration
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Author:  boumay [ Fri May 22, 2015 11:59 pm ]
Post subject:  Calibration frustration

I have some major questions about the calibration phase, because I really don't grasp it.

I have a 4m by 5m room, 4 ps-eyes, each camera placed at a corner of the room and each has an height of approx. 1m55 (except at 1.65). Capture area is 1m50 x 2m, marked by 4 ground markers white tape.

- Does the flashlight bright dot has to be small, or is a 3cm light bulb ok?
- Which camera is number 1 and which is number 2, etc, in ipi recorder, (from up-left to up-right, then down left to down-right?) Which actual physical camera we give number 1 and so on?
- Why does cameras don't have the rigcorrectht height in the software (I did set the correct distance between cam1 and 2, but the cameras are way too high or too low in the software)
- Why does the red tracking square often prioritize tracking of much lower (duller) spots before tracking the actual flashlight (it tracks reflections on tables, walls, even white tape markers put on the ground, and this is occuring most of the video lenght.

At the end, the calibration is a total failure, they are mostly red dots everywhere, the cameras/everything are rotated in wired direction, upside/down etc.

I would like to post the post, but it is approx 2 to 10gb big.

I hope my issue is understandable.

Author:  vmaslov [ Sat May 23, 2015 6:17 am ]
Post subject:  Re: Calibration frustration


Small light sources are preferred. However, what actually matters is the size of a produced light spot in video, not the physical size of a bulb. For example, 4.5cm light sphere of PS Move produces the same light spot on video as 1cm flashlight in candle mode.

Marker recognizer looks for a light spot of small size in a frame. If your light is large, try to use Large for marker size (under Manual Calibration Adjustments).

Cameras are numbered from top-left to bottom-right, rows first. You can see the numbers when you hover the screens. For example, 'PlayStation Eye #2'. You can order cameras as you wish by dragging screens on Setup tab. Usually, clockwise or counter-clockwise order is convenient.

Because calibration has failed, you cannot expect that cameras are positioned correctly. So heights may not correspond the distance. Also, for correct height proper ground plane should be determined (you should mark the floor in several points during calibration video).

You may pass your video files via any file-sharing service like Google Drive or Dropbox.

Author:  boumay [ Sat May 23, 2015 8:11 am ]
Post subject:  Re: Calibration frustration

Thank you for answering.
I understand the statements. Except the ground point "manual" setup, I don't see any section with that option. I also don't see a "Manual Calibration Adjustments" section where I can adjust large for marker size.

And now I'm trying the half-circle configuration at it seems that 4 corner setup doesn't work for 4 cameras.
I got a less catastrophic result so far but still a failure.

Some last questions would be: do the bright spot has to be on the 4 cameras at the same time, if only 2 or 3 of the cameras catch it, is it enought to get a good calibration?
And, how to move a camera down only in the z axis so it doesn't move left or right?

Thank you again.

Author:  vmaslov [ Sat May 23, 2015 3:30 pm ]
Post subject:  Re: Calibration frustration

Manual Calibration Adjustments are on the Calibration tab. See the screenshot in attachment. You can also see there buttons for working with ground points in case the ground was not detected correctly by the program after the calibration.

The light should be seen in as many cameras as possible. Having only 4 cameras, it's quite easy to make it visible to all cameras at once with a little practice. One technique that some users employ for that purpose is to attach the light to an end of the stick to minimize the occlusion by a person's body.

There's no way to limit camera movement to vertical axis. I do not recommend to do any manual editing of camera positions in your case. Automatic detection of initial camera positions (turned on by default, you can also see this option on the screenshot) works very reliably for 4 cameras.

manual-calibration-adjustments.png [ 17.37 KiB | Viewed 10466 times ]

Author:  boumay [ Sat May 23, 2015 7:25 pm ]
Post subject:  Re: Calibration frustration

Thank you very much for your information.
I'm getting better at it since yesterday :))
But I think I don't have the same version as yours because I don't have the mentionned options (see pic)

Capture.JPG [ 46.63 KiB | Viewed 10464 times ]

Author:  Snapz [ Sun May 24, 2015 7:28 am ]
Post subject:  Re: Calibration frustration


That is Version 2 of iPi Studio, but the calibration process is the same.... with 4 cameras in that version it is a bit more touchy to get good calibration, and a lot slower in processing it, but it will calibrate fairly well once you get the "trick" down.

I will let iPi explain their version of the process they recommend, as not to confuse you.


Author:  boumay [ Sun May 24, 2015 12:23 pm ]
Post subject:  Re: Calibration frustration

Thank you :)

Author:  vmaslov [ Sun May 24, 2015 11:38 pm ]
Post subject:  Re: Calibration frustration

Yes, indeed. Your screenshot is from version 2. You should have mentioned that before as we naturally assume the latest version by default.

It does not have the option for marker size. However, the calibration for 4 cameras is very reliable as well given a proper calibration video. You can see a sample of calibration video in our wiki:
I hope you've also studied the 'Calibration' part in our docs thoroughly:

In case of having further problems with calibration, I encourage you to share one of your videos so we could give you specific advises.

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