Shoot and run using MIDI
Screenshot from the game as art (or art as game)
Jeff Koon must die!!! by Hunter Jonakin
I just learned from Nils Peters that the MIDI specification was extended in 2009 with a set of descriptors for Three Dimensional Sound Controllers. According to MMA “the advancement of the MIDI standard from simple stereo rendering to true three-dimensional sound rendering becomes the next logical step in MIDI evolution.”
The specification is motivated from use in gaming and virtual reality, and settles for using a spherical coordinate system rather than Cartesian, using “azimuth angle, elevation angle, and distance to describe the object, much like firing artillery.” I have never though of spherical coordinates in terms of “shoot and run” metaphores before, but then again I am a pasifist, so what is to be expected?
Parameters for distance attenuation in the MIDI specification.
The MIDI specification uses 14bit RPN (Registered Parameter Numbers) for parameters. There are several interesting points in the specification, including:
- A navigational coordinate system is used. 0° is in front, +90° to the right and -90° to the left. 14 bit resolution azimuth is described wih a step size of 0.02°.
- Elevation is full circle (-180° to 180°) rather than -90° to 90°.
- Distance is defined as a ration to the maximum distance permitted: The distance ration parameter controls the ratio of the current distance that an object is away from the listener to the maximum distance. There are additional parameters for setting maximum distance, gain at maximum distance, and a reference distance ratio. The relationship between these parameters is illustrated above.
The specification also propose default equations for distance attenuation, and a second alternative attenuation scheme “found in the litterature”. This second scheme is the same that we use for distance attenuation in DBAP (Distance-based amplitude panning).
Also of interest at the MMA web site is a white paper from 2008 comparing MIDI and OSC.comments powered by Disqus
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