Calibration bug/Problems in David 5 Dual Camrea.

[micr0]

There is a bug that I found when Sven released the Beta of David 5 to the group and it seems the bug is still active in the current release. It was a problem with the "OptimizeMultiCameraCalibration" setting. When enabled it was causing bad distortion in the scans. When calibrating with the setting on it returned a different camera calibration then with the setting off. David was reporting different camera angled with the setting on and with it off, even though the hardware (cameras) were not moved. Though I was able to tell Sven about it on the old forum, I never heard that anything was ever discovered by the David team. Tonight I was working and noticed that I wasn't getting good calibration with a set up I had and after failing to solve the problem enabled the " OptimizeMultiCameraCalibration" setting. The next calibration seemed excellent, but again when I started scanning, the scans were distorted and didn't align well. Dr or other David people: can you find out if Sven ever found out why that setting is causing problems? All the pictures and details of what I'm talking about are here: http://forum.david-3d.com/viewtopic.php?f=16&t=6770&start=120

[SvenMo]

Hi Micr0,

I am sorry I lost sight of your post and didn't reply yet. :-( Thanks for your reminder!

Your bug is hard to reproduce, but it can happen - depending on the positions and orientations of the hardware components. We are investigating it, and I'm confident we will find a solution for one of the next releases.

If "OptimizeMultiCameraCalibration" creates distortions so regularly with your system, then please switch it off for now. The more precise your system is (especially precision of calibration panels, 90° angle, and quality of camera lenses), the less important is "OptimizeMultiCameraCalibration".

Sven

[micr0]

Thanks Sven. Two things you should note: 1)when I ran calibration on a recent set up the black and white squares displayed at the end of a successful calibration didn't fully align up with the dots on the calibration panel. When I switched the optimize setting, on they did, but the scans were slightly off. 2) The calibration figures for the same set up (camera and projector angles etc) are different when the optimize setting is on and when it is off. So David is deriving the camera angles/position relative to the projector differently depending on whether optimize is on or off. Hope this helps.

[SvenMo]

Yes, this helps - thanks!

[avogra]

Sven, the problem I described here Dual-camera-calibration-off seems to be related to micr0's problem. Maybe it helps in tracking it down.

[SvenMo]

Hi micr0,

Sorry, better late than never...

We have been and still are investigating the calibration. I found that "CompensateAngleBetweenPatterns" might be the cause for your distortions.

In version 5.0.x, there were several "Compensate..." options in the Advanced Settings. However they were used only for normal camera calibration. During MultiCameraOptimization ("OptimizeMultiCameraCalibration" setting), those settings were not followed, instead PatternOffsets and AngleBetweenPatterns were always compensated.

Now in version 5.1, there are additional Advanced Settings for MultiCameraOptimization.

I still believe that the default settings are the best for most users and setups. But for your problem, it might be interesting to switch OptimizeMultiCameraCalibration back on, but switch MultiCameraOptimization -> CompensateAngleBetweenPatterns off.

If you want, please test that and let me know.

Requirements: precise 90° corner, let projector run warm before calibration.

Sven

[micr0]

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SvenMo wrote:

Hi micr0,

Sorry, better late than never...

We have been and still are investigating the calibration. I found that "CompensateAngleBetweenPatterns" might be the cause for your distortions.

In version 5.0.x, there were several "Compensate..." options in the Advanced Settings. However they were used only for normal camera calibration. During MultiCameraOptimization ("OptimizeMultiCameraCalibration" setting), those settings were not followed, instead PatternOffsets and AngleBetweenPatterns were always compensated.

Now in version 5.1, there are additional Advanced Settings for MultiCameraOptimization.

I still believe that the default settings are the best for most users and setups. But for your problem, it might be interesting to switch OptimizeMultiCameraCalibration back on, but switch MultiCameraOptimization -> CompensateAngleBetweenPatterns off.

If you want, please test that and let me know.

Requirements: precise 90° corner, let projector run warm before calibration.

Sven

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Thanks Sven.

I look forward to trying this. I'll report back as soon as I can.