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Hi. Firstly I'd like to say that your tracking solution is outstanding and my University department where I work has purchased an 8 camera tracking setup from you on my recommendations and I intend to have them purchase more. Keep up the great work guys,

On to my problem.

I am using a single Flex c120 camera to track 9 markers placed on a persons face. I have this implemented successfully but I am have problems with regards to the order in which the camera is picking up and tracking these objects. I am using the position of each marker to do simple trigonometric calculations such as calculating angles between certain points.

But unfortunately I am unable to ensure that the camera tracks points in such a regular way that if each point is stored in an array eg points[9], the marker stored for example in position 0 (points[0]) will always be the same marker on the same position of the persons face during each recording session. Is there any way to ensure that the camera picks up markers for example from the top left of the cameras view area ie the closer to the top left is the first to be tracked?

Thank you for you time and I hope I have been clear in my explanation of my problem.

Paul Smith

Also i am programming in c++.
Thanks
Paul

You are using the standard OptiTrack SDK?

For individual 2D points the SDK software does not provide tracking of points between consecutive frames, it will only return information about the markers found in the current frame. There is also no guarantee markers will be delivered in the same order from one frame to the next (no sorting).

Hi. I'm using the standard Optitrack SDK yes. I'm tracking in real-time so the current frame is all I am concerned with. Is there no way of influencing which marker is delivered first at all? What algorithm is used in this process? I seem to only have problems with in what order the first out of 4 markers are tracked. Also what effect will changing NP_OPTION_SCORING_ENABLED to False for the camera object have if any to this order? cheers.

Paul

cheers anyways. I'll just sort them manually I guess. thanks for your help.

Paul

You may want to see if there is any open source frame-to-frame object tracking code available in Touchlib, their website is http://www.nuigroup.com/ .

as Birch says, the problem of stringing frames together is not one that the OT baseline SDK solves for you.

I have an explanation of a lot of this kind of thing posted here:

http://fie.us/blog/mocap_series/

If you are doing a 2d solution rather than 3d, you will find some of the suggestions to be a bit much. But the basic concepts are similar. enough to give you the idea.