6DOF values changes while object is fixed

[Matan]

Hello,

I recently bought TrackIR and orderd OpticTrack System together with the vector expansion unit.

The SDK (4.1.048) is great, I was able to test application samples in no time. Also from the first look the tracker has real potential. That's why I have several questions regarding 6DOF tracking:

1. I have executed OpticTrackSample with TRACKIR camera. After I have "opened" my camera and "start" - all the 6DOF tracking points values were continuously changing, altuoght the tracked "vector expansion" is not moving at all !?
1.1. Why do the application sence these movments ?
1.2. Is it related to the smoothing algoritem?
1.3. How can it be a voided ?

2. As I have noticed in TRACKIR application at the "Motion Preview window" (Heads and Gauges) this event doesnt occurs, can you please explain why.

[Birch]

Just to clarify, it sounds like you are using the OptiTrack SDK (v1.0.028)? It is the one which can be downloaded from the OptiTrack website.

Answers to your questions :
1. The will be a small amount of noise present in the resolved location of the Vector clip (to the right of the decimal place), is this the type of noise that you are observing? If so, it will be most noticable when "smoothing" is not being used on the tracking data. Also, make sure (in the tracking window) that the camera is tracking the objects which you intend it to.

1.1. The application is set to display all of the information available. If you want to ignore some of the noise, you can truncate or smooth the data.

1.2. Possibly yes (see above). The smoothing will manifest as rapid changes in values in response to large changes, and a gradual "sliding in" to the actual values in response to small changes.

1.3. (see above)

2. The Heads and Gauges windows in the TrackIR software utilizes some of the same core functionality and technology that the OptiTrack SDK uses. In the TrackIR software user interface, we only display the larger changes in the data which means information below the noise level is not visible.

[Matan]

Hi
It took me time to response since I have waited for the arrival of 3 OptiTrack.
The SDK in the purchased disk is 1.0.023. Is it better to download the SDK from the web?
Here some additional questions:

1. The dot noise value changes also some amount of value left from the decimal dot.
2. While value is changing (noise), the dot in the �Camera Image� panel seems to be stable. Can you please explain this phenomenon.
3. Is it possible to get �The Heads and Gauges� windows, source code (in the TrackIR software).

Thanks
Mat

[Birch]

1. The X,Y location change and noise for a tracked object is a function of the amount of movement, the amount of edge noise and its size (in pixels). Small objects will be more sensitive to the changes of a single pixel than objects with larger areas since the X,Y location is a weighted average.

2. Our optical tracking cameras are fairly sensitive, a configuration which appears stationary might be exhibiting small changes.

Things which can affect dot position :

• Vibration or other movement of the camera
• Vibration or other movement of the tracked objects
• Changes in ambient lighting
• Movement of other objects which affect lighting
• Pixels at the edge of the object whose intensity may be oscillating above and below the threshold value

Keep in mind that the video preview window is usually not displayed at the full 120 frames per second that the camera is producing (in order to reduce CPU utilization). Also, the human eye might not easily distinguish single pixel changes at the full frame rate.
3. The heads and gauges source code for the TrackIR software is not available to the public, though it is good an example of what could be built with the capability provided by the OptiTrack SDK.

[ February 03, 2006, 04:16 PM: Message edited by: NaturalPoint - Birch Zimmer ]

[yoshi]

Have you tried removing the smoothing calls in UpdateDotInfo()? I think that will stop the drifting.

[Matan]

Hi
I have checked this issue again. I also had record it on my DV camera.
The optiTrackcamera and the targets were stable at the range of ~60 cm and I got the following position drifting:
At Time = 0 the position: 215.016 143.341
At Time = 50sec position: 217.023 143.367

Is this kind of drifting is suitable?
After a while lets say 2 minutes the positions will get to a stable state

Thanks
Mat

[Matan]

Yes,
Although I do not get drifting, I get the values to �jump�.
Most of the changes are the 1/1000 and 1/100 in the position, but I also got some changes in 1/10 and complete integer
This situation might occur in my future object tracking application, and might indicate false movements.
How can I prevent / fix it or Indicate the specific situation and ignore these false tracks?

[Birch]

quote:Originally posted by Mat:
Yes,
Although I do not get drifting, I get the values to �jump�.
Most of the changes are the 1/1000 and 1/100 in the position, but I also got some changes in 1/10 and complete integer
This situation might occur in my future object tracking application, and might indicate false movements.
How can I prevent / fix it or Indicate the specific situation and ignore these false tracks?You may want to look into recording the values over time for some post-processing analysis. You could then review the data set afterward to determine whether the noise level is going to be acceptable for your project and whether there is a possibility of implementing a smoothing and filtering algorithm that would deliver suitable responsiveness and stability.

[roman tunkel]

quote:Originally posted by Mat:
Hello,

I recently bought TrackIR and orderd OpticTrack System together with the vector expansion unit.

The SDK (4.1.048) is great, I was able to test application samples in no time. Also from the first look the tracker has real potential. That's why I have several questions regarding 6DOF tracking:

1. I have executed OpticTrackSample with TRACKIR camera. After I have "opened" my camera and "start" - all the 6DOF tracking points values were continuously changing, altuoght the tracked "vector expansion" is not moving at all !?
1.1. Why do the application sence these movments ?
1.2. Is it related to the smoothing algoritem?
1.3. How can it be a voided ?

2. As I have noticed in TRACKIR application at the "Motion Preview window" (Heads and Gauges) this event doesnt occurs, can you please explain why.I am very much a novice in this area.
Because of that, can you give me a hand - how did you do it?
Thanks in advance, and please respond privately.