View Full Version : Walking is reversed in X and Z axes with motion capture.

07-16-2018, 07:40 AM
When a user, wearing the tracking marker, is walking in the real environment, the Vizard virtual environment moves oppositely in the X and Z axes.

Walking left shows walking right on display
Walking right shows walking left on display
Walking forward shows walking backward on display
Walking backward shows walking forward on display

The Y axis is correct - i.e. moving the marker up shows upward translation on the display. Rotations are also correct.

The nature of this motion leads me to believe that Vizard thinks the marker is on the back of the body/head. If this were the case, then the tracking would be correct. However, given our camera setup, the tracking marker will be on the front of the HMD facing the cameras. Attached is a diagram of our setup for clarity.

I've tried every alignment iteration in Optotrak and still get the same problem every time. I am connecting to Optotrak via the below script. I haven't used VizConnect for this yet. Is there something that I can add in the script or specify in Vizconnect to get the X and Z movements to display correctly?

opto = viz.add('optotrak.dle')
body = opto.getBody(0)
viz.link(body, viz.MainView)


07-25-2018, 08:47 PM
In a previous (https://forum.worldviz.com/showthread.php?t=6147) thread it seemed like you had a similar issue and that was resolved. Is the camera location different in this current setup?

07-31-2018, 07:18 PM
It wasn't necessarily resolved. It just only works the way I want if I have the marker on the back of the head. However, I want it on the front of the head.