View Full Version : Tracking Multiple Lights

04-05-2005, 01:45 PM
We're trying to track two lights that will be between 0.5 and 4 meters apart. We've tried using code we've used before for tracking head + hand, but we're running into this problem where the PPT doesn't seem to track the two lights properly when they are far apart.

On the PPT display, when only one light is on, the coordinates are fine and correct, but when two lights are on, moving one light changes the coordinates of the other and the coordinates themselves are wrong - so a light at 0,0,3 (with one light) becomes 0,0,1 (with two lights) for example.

Any ideas about what's going wrong?

04-05-2005, 01:55 PM
Hi Nick,

Most likely your version of the PPT software is only configured for head-hand tracking which requires a certain vertical separation for the markers for all four cameras. Depending on how the cameras are mounted and potentially tilted, the horizontal up/down split does not work when the markers are moved apart in the room.

The newer versions of the PPT do not have this restriction and can track up to four points.

Can you let me know which version of PPT you are running? The version is indicated in the lower right corner of the PPT interface.



04-05-2005, 02:53 PM
Version 1.22

That sounds like it might be the problem.

04-05-2005, 04:50 PM
Please send me an email to pusch@worldviz.com and I'll
send you the download link for a PPT upgrade.

Best, Matthias

12-15-2005, 04:52 PM
hope you have been doing well.

We just tried to add a pointing-device consisting of two lights (3rd light is on HMD).

We spent a lot of time trying to make it work, it seems that the lights are flipping when I turn the stick they are attached to over the the horizontal. (We saw that in the ppt-tracker (without communicating)) and the simulation?!

What can we do?

If there is no solution for the light-Problem, would the following be a workaround?
Do we have to add another intersense on a serial port (on new serial card)?

Thank you,

12-19-2005, 04:51 PM
Hi Johannes,

I don't fully understand what you are trying to do.

The PPT is designed to be a optical/intertial hybrid system, so clearly for a 6DOF pointing device we would recommend to use an Intersense InertiaCube2 (with wire) or InertiaCube3 (wireless) in combination with one tracked LED marker (wireless).

On the other hand, if you want a handheld pointer (i.e. a 5DOF tracked device), you can indeed use two LEDs for this. The PPT itself does not give you their identities (which could explain why you saw things 'flipping' like you reported), but typically they are mounted on the handheld device at a fixed distance, which is all the information you need to make it work.

Please contact me directly at pusch@worldviz.com and we will provide you with a sample script for such a pointer application.

Have fun!

The WorldViz Team