WorldViz PPT-E, Руководство по эксплуатации, Страница: 73 / 163

Using 3D Data
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LOCAL OFFSETS
Often it is impossible to locate the PPT wireless marker at the optimal location for
tracker. For head tracking with head-mounted displays, the ideal marker location is
at the center of the user's eyes. However, to maximize marker visibility, most user's
mount the marker on the top of the head-mounted display. This causes the user's
virtual view to incorrectly move forward when they pitch their head down.
Since the local offset between the marker and eye is typically fixed, the PPT system
can make this correction in absolute global coordinates for you if your are running
your PPT with
orientation and position tracking . Note that the Local offset plugin
requires orientation information, or it will print an error message and not apply any
offset.
To apply a local offset:
1. Measure the offset in millimeters of the location of the PPT wireless marker IR-
LED relative to the desired report location (generally the location of the user's
eyes in a HMD). Make these measurements in local coordinates in which right
is +X, up is +Y, and forward is +Z.
2. In the Configuration Pane, add a "Local offset" Post-process Plug-in if it is not
already added.
3. Click the Configure button, right click and select Add, and enter your offset
values in millimeters.
4. In the Configuration Pane, make sure a plugin supplying orientation
information is active before the Local offset plugin. You can drag the plugins to
change their order if necessary.
5. You can remove or edit an existing local offset by right clicking on the offset
and selecting the desired option.
Examples:
1. If your marker is mounted on a 30 cm vertical pole above the eyes on a HMD,
the offset to apply would be specified as X=0, Y=300, Z=0.
2. If your marker is mounted in front of the HMD, and there is 100 mm to the
eyes, the offset to apply would be specified as X=0, Y=0, Z=100.
3. If your marker is mounted so that it is 10 cm above the eyes, 2 cm to the left
of the center of the HMD, and 5 cm behind the eyes (the marker is above the
user's head) then the offset to apply would be specified as X=-20, Y=100, Z=-
50.
LOGGING DATA
Use When:
 You want to record the marker data Logging data from PPT into a text file.
Software Configuration: