Motion Capture Discussion Group Homepage

• Announcements
• Reading Group
• UBC Motion Capture framework
• Schedule
• To Capture
• To Buy
• Q&A
• Our Notes
• Vicon Manuals

Announcements

• from Kang: I've processed a small portion of our Jun1 data. Contact me if you wanna practice your iQ skills.

Schedule

To Capture

• Michiel doing cartwheels

To Buy

• Mo-cap suits ... (current is a large) and maybe sleeve-less (vest)
• Hygienic/medical tapes for direct skin attachment
• Soft markers for capture when performing moves involving contact
• Black duct tape
• Velcro tape (black) ... fuzzy side
• Measuring tape

Q&A

1. Q: What dynamic calibration is for?
   • A: from P21 of Vicon System Manual
     Static calibration calculates the origin or centre of the capture volume and determines the orientation of the 3D Workspace.
     Dynamic calibration involves movement of a calibration wand throughout the whole volume and allows the system to calculate the relative positions and orientations of the cameras. It also linearises the cameras.
2. Q: What to do if residuals are still too high? What should they be to begin with. what do they mean?
   • A: from P23 of Vicon System Manual
     A residual for each camera is a measure of the accuracy of a single camera. They are larger the greater the distance of the camera from the capture volume and are measured in millimeters. It is the root mean square of the distance between two rays; the first being that from the centre of the strobe ring to the centroid of the marker and the second being the reflected ray from the marker to the camera lens.
     Residuals should be less than 0.1% of the distance from the camera to the centre of the capture volume. For example, our cameras are roughly 3~4 meters from the centre of the volume, the residuals should be less than 3~4mm. So we are good with a 1mm mean residual. Consistency between residual values from all cameras is also important.
     Residual values much higher than those given here may indicate a problem. Mathematically it means that the calibration algorithm failed to converge to a meaningful result. Extraneous reflections or flickering light from elsewhere in the capture space, or reflective material from the person performing the calibration and wand waving might be the noise sources. Try checking the live monitors for additional sources of light.
3. Q: Why are we getting zero wand visibility?
   • A: from Derek Potter of Vicon Support
     The measure of wand visibility does not appear in all versions of workstation. Its not really and important number to have access to anyway. Its most for user feed back when a calibration fails or is very poor. If all cameras could see all marker on the wand on every single frame then wand visibility will be 100%. Normal is anywhere between 50-80%. This number is normally only import when the cal is bad (for your system -- Greater than 1.5 mm residual). If you had a bad cal and a very low wand vis% it could indicate to you that when performing the dynamic cal you were waving the wand outside the area where the cameras are aimed.
4. Q: Why we got bad static reproducibility?
   • A: from Derek Potter of Vicon Support and Kang
     The 5% static reproducibility however is a little. The first thing you should do is take a look at your L-Frame (Ergocal). Make certain 1. The frame is not bent; 2. All 4 markers are at the same level (height - Z); 3. When placed on the floor the L-Frame is level; 4. Measure the distance between the marker on the L-Frame and compare this number to the what is inside the ergo.cro file. Make sure they match exactly.
     We had been using [3B) Ergocal 9.5mm mkr - 390mm Wand 25mm mkr]
     6
     20 30 41.75
     180 20 41.75
     260 20 41.75
     20 260 41.75
     390 0 0
     130 0 0
     However, after measurements, I think the first marker should actually be 30 20 41.75. I reprocessed the camera calibration, and got 1.1%. It is not great, but definitely better.
5. Q: What is camera masking? How do I use this functionality? Why should I use this functionality?
   • A: CameraMask.htm

Our Own Notes

• MotionCaptureWorkflow.ppt: basic steps for mocap
• Jun1MocapNotes.doc: mocap notes taken on June 1, 2005
• iQSteps.doc: Basic iQ postprocessing steps
• DataPath.gif: Data Paths for the Vicon

Vicon Manuals

• All Vicon manuals can be found on mocap C:\Program Files\Vicon\Documents; All iQ manuals can be found on mocap C:\Program Files\Vicon\VICONiQ 1.5\Documentation. Some of the manuals can be found below.

• 1.IntroducingVicon.pdf: Vicon Manual

• 2.Preparation.pdf: Vicon Manual

• 3.EssentialsofMotionCapture.pdf: Vicon Manual

• 4.Systemoptions.pdf: Vicon Manual

• 5.AdvancedCaptureTechniques.pdf: Vicon Manual

• 6.Reference.pdf: Vicon Manual

• 7.DVCapture.pdf: Vicon Manual

• 8.EclipseManual.pdf: Vicon Manual

• iQ1.5_Glossary.pdf: iQ1.5 Manual

• iQ1.5_HotKey_Layout.pdf: iQ1.5 Manual

• iQ1.5_Introduction.pdf: iQ1.5 Manual

• iQ1.5_Tutorial_Modelling.pdf: iQ1.5 Manual

• iQ1.5_Tutorial_RealTime_Mode.pdf: iQ1.5 Manual

• ViconVFileFormat.doc: if you want to understand Zhijin's c++ vfile reader, which is based on Kang's java vfile reader

• The Vicon Online Support website features a database where you can search for answers to various issues with the Vicon Motion Capture system. You need to get a username/password to access it, easily obtained by contacting support@viconpeakDELETEthisTEXT.com and mentioning Michiel van the Panne.

• ViconPeak Video Training Library (Password = vicon)