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B Technical Appendix
•
origin is the center of the (partial) sphere that forms the finger tip,
• the +X axis is oriented in direction of the outstretched finger,
•
the +Z axis is defined to form a normal on the finger nail, pointing upwards,
• the +Y axis is defined with these specifications, resulting in a right-handed coordi-
nate system.
For the left hand see figure B.2 on page 257, for the right hand see figure B.3 on page
257): Given the length of each phalanx and the angles between them, it is possible to
reconstruct the entire finger.
Z
The data shown in the Fingertracking display is NOT the position of the
finger tip! For calculating the finger tip position you need to consider
radius R like shown in figure B.2 on page 257.
Z
Note that the joint between innermost phalanxes and back of the hand
can move! This corresponds to a bending of the hand’s back.
B.2 Output of Measurement Data via Ethernet
DTrack2 uses ethernet (UDP/IP datagrams) to send measurement data to other applica-
tions. The IP address and the port of the application (and the computer it runs on) can be
configured in
Settings
→
Output .
Each datagram carries all the results of a single measurement, coded in ASCII format.
One datagram is sent after each measurement of the cameras, i.e. following the synchro-
nization frequency. The ’
send data divisor ’ in Settings
→
Output offers the possibility to
decrease the data output frequency (
f
output
= f
sync
/d
divisor
).
i
All data are given in units millimeter (
mm
) or angular degree (
deg
/
◦
).
ART provides free sample source code (‘DTrackSDK’, in C++) to receive and parse the
output data. Please contact ART to get it.
A UDP datagram in ASCII format contains several lines separated by CR/LF (hex
0D 0A
).
Each line carries data of a specific type and starts with an identifier. In Settings
→
Output
you may configure which lines or data types should be included in the output:
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