How to track the actual viewpoint

[Jerry]

When tracking the position of the observer's viewpoint using
the PPT tracking system, ideally the tracked LED should be
located between the observer's eyes since that is where the
egocentric viewpoint is located. However, this is impossible to
achieve and so the LED is usually fixed to the HMD at some
position offset from the viewpoint. I realize a preTranslation
of the link between the PPT and the viewpoint can be used to
initially place the tracked location between the eyes, but
if the observer rotates the head that offset is no longer valid.

Is there some way to combine the PPT and an orientation sensor so that
the viewpoint can be placed between the eyes despite translations and
rotations of the observer?

[farshizzo]

You need to combine the position and orientation tracker into one object, then use the preTrans operator on the link. Example:headTracker = viz.mergeLinkable(posTracker,oriTracker)
headLink = viz.link(headTracker,viz.MainView)
headLink.preTrans([0,-0.01,0.01])

[Queequeg]

Hi,

I don't know if this thread is too old but I'll still try:
Do I need to use the offset from the tracker to the HMD's lenses or to the point between the user's eyes?

Thanks!

[Chris Coffin]

Ideally you're offsetting to the point between the user's eyes. Internally, Vizard will determine the left/right eye positions based on the center point of the eyes offset to the left/right by the IPD relative to the orientation of the view (half IPD to left half IPD to right).