Java Reference
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pIckInG In a vIrtual Instrument panel
We will now outline a more complete and interesting application to implement the front panel
of an instrument in a 3D virtual laboratory using the various picking techniques discussed
(Xiang, 2001). The entire system involves the rendering of a Java 3D based laboratory in
a room with an oscilloscope and one signal generator for carrying out a real-time real-life
experiment. The virtual instruments that the user can operate on remotely in a client Internet
site actually correspond to equivalent real instruments in a physical laboratory.
After navigating to the instrument of interest in the virtual 3D world, the user can use
mouse drag, press and click to adjust the various types of controls such as pushbuttons,
sliders and knobs on the instrument. Any change in the instrument control panel will be
transmitted to the server, which will send commands to change the actual settings on the
real instrument in the laboratory. The resulting changes in waveforms and other measure-
ments will also be sent back to the client to provide update in the Java 3D virtual world
on the client side.
In this application, many objects corresponding to a variety of control knobs, slid-
ers and pushbuttons may be picked and different controls will have different behavioral
requirements. Illustrated to some degrees in Figure 25 in the control panel for the signal
generator, a knob can only be turned, a pushbutton must be pushed in a certain direction,
and a slider can only be dragged in a specific direction.
Figure 25. Signal generator control panel
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