Game Development Reference
In-Depth Information
For each joint, calibration
involves placing your model into
the default relaxed position and
then capturing the voltages for
each joint at this position. Store
both the current joint orientation
and the voltage. Now rotate the
upper body device to the max-
imum for a single Euler angle for a
single joint. If we think of the
shoulder and the amount this can
move in bank, then it would reach
a maximum when directly rotated
upwards. Move the digital model to
this position using mouse move-
ment inputs, then connect the
model's orientation to the voltage being recorded for the shoulder bank
potentiometer. At this stage you have a direct link between the digital
output of a single potentiometer from the input device and the orientation
of the bank for the shoulder. If you repeat this for each potentiometer you
will have a full suit calibration. Having set this once, save it to a file that
can be reloaded.
Since the equipment you will use is likely to differ depending on
available resources, the presentation is deliberately an overview, but in
the following section we will look at how a particular A/D converter was
used to provide the continuously scanned input for an upper body real-
time character suitable for use at exhibitions and shows. It is possible to
link an upper body input device with jaw movers that are created in just
the same way.
By allowing two operators to provide the input you can capture in real-
time to a file or straight for display the motion of a dynamic character. This
type of input device, being relatively low cost and easy to set up, is ideally
suited for exhibition and show use.
Figure 12.7 A three-potentiometer joint.
Capturing data with your mocap suit
Potentiometers and voltage are linked by the important relation V = IR ,
where V is voltage, I is current and R is resistance. The following section
is based on the low cost 12-bit A/D converter from Computer Boards (tel.:
+1-508-261-1123). The board CIO-DAS08/Jr-AO provides eight digital
inputs and outputs, eight analogue inputs and two analogue outputs.
Since we are using a multiplexer we can use the digital output lines to
 
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