Angle of camera on Vicon

[Yoann]

Hi,
I would like to have the angles of the cameras on Vicon-Nexus. I have seen that there is a section orientation in the xcp file, but I don t understand the meaning of the 4 values. Could you help me please?
Thanks.

[Tim Wrigley]

Re: Angle of camera on Vicon

I believe it's an axis-angle representation: a unit vector representing an axis in space, followed by a rotation about that axis (in radians).

Tim Wrigley
University of Melbourne

[Yoann]

Re: Angle of camera on Vicon

Hi,
Thanks for your answer.
I don t think that it is this kind of representation. The norm of the 3 first values is not 1... However the norm of the 4 values is exactly 1.
I still don t know how I can deduce the orientation of the camera.

[Tim Wrigley]

Re: Angle of camera on Vicon

Hmmm .. interesting. Vicon have historically used helical axes or axis-angle for this type of thing (although in the pre-Nexus camera cal CP files it was a full rotation matrix). From your findings this one sounds like it might be a quaternion.

Why don't you ask them ? :-)

I'm writing some code currently to detect changes in calibration over time from stored XCP files, so I will be interested in the answer.

[Dr Iain Charlton]

Re: Angle of camera on Vicon

Hmmm .. interesting. Vicon have historically used helical axes or axis-angle for this type of thing (although in the pre-Nexus camera cal CP files it was a full rotation matrix). From your findings this one sounds like it might be a quaternion.

Why don't you ask them ? :-)

I'm writing some code currently to detect changes in calibration over time from stored XCP files, so I will be interested in the answer.

The ORIENTATION attributes in the KeyFrame and ControlFrame elements in XCP files are quaternions with the w element last, so they are "x y z w". See http://en.wikipedia.org/wiki/Quatern...atial_rotation for a good description of how to turn these into rotation matrices.

Iain Charlton