Any way of knowing if a tracker is lost?

[shivanangel]

Hi,
I was wondering if there was some way for the PPT tracker to tell Vizard
through the VRPN 7 interface that a tracker has been lost.

An example would be:

I am using three LEDs to track on object and its orientation. If due to
a human occluding one of the trackers, or just a situation where the cameras
can't immediately see all 3, is it possible to communicate that a tracker has
been dropped.

Currently, it just seems to transmit data from the last point in history and
snaps to a previous location when dropped.

Any way I can alert Vizard about this drop so that I can handle this case?

Thank you,
George Lecakes

[Notch]

It seems this question was posted over five years ago, with no reply... I'd also like to know the answer to this question, if there is now a solution?

[Jeff]

The tracker will report the last know location once its lost so you can check the current value against the previous one. Or you could use the waitForSample method on the vrpn tracker object to see if new data has arrived within the specified timeout period.

Also we'll look into having PPT's VRPN server send a NULL signal to Vizard when a tracker gets lost.

[masaki]

Just wanted to give a quick update. We just identified a bug in our PPT VRPN7 plugin that resulted in PPT sending data even if the Marker is not valid (from occlusion, dead marker, etc). So because of this, using waitForSample will still give a false positive. The fix for this will be coming out in a new installer of PPT soon and you'll be able to call waitForSample, and then it will return False if the Marker is not valid. I'll update this post when the new installer is ready.