Technical Challenges


One of the biggest challenges for the project was getting both computers to communicate with each other through MIDI.  With a very assorted collection of gear including a MINI Macman interface, and a Tascam US-428 controller, it was possible to jerry-rig a system that seemed to work fairly well, with the occasional MIDI port overload.  Every so often, when the dancer’s movement became extremely active for an extended period of time, the MIDI port would choke on the flood of data causing OMS (the MIDI driver for Max) to freeze-up.  This was easy to observe by sending in children to play in the motion-capture space; with their zealous enthusiasm and unmitigated energy they proved to be among the best extreme "beta-testers" for the system.  To get around this problem, a set of filtering subroutines (“speedlim” objects) were inserted into the Max algorithms to insure that the data would not overload the MIDI port.

Other problems that were encountered concerned mostly the video and its analysis.  In trying to get accurate data about the dancer's location, it was crucial that the cameras were locked down, did not change their view, and were not otherwise adjusted in anyway.  Once this was fairly secure, it was observed that the angle of the track lighting on the ceiling was creating long shadows from the dancer's body.  To circumvent this problem, the lights were angled to be more perpendicular to the floor and focused around the center of the motion capture space.  The settings within Cyclops had to be fine-tuned as well, for example, the threshold value couldn't be too sensitive or minute changes in ambient light intensity could be recorded as motion, and conversely the threshold value had to be sensitive enough to respond to subtle movements by the dancer.  In order to gain increased sensitivity, the decision was made early on to switch from a 5x5 grid in Cyclops to an 8x8 grid.  This proved to be a magic number since it allowed the dancer's body, when they were standing in a central location, to be divided up into enough segments to capture their movement in isolation.  It also kept the processing time low and cut down on latency; and as an added bonus allowed for a direct numerical correlation to MIDI (which uses 128 as its range of values).

 

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