ReacTable
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- The correct title of this article is reacTable. The initial letter is shown capitalized due to technical restrictions.
The reacTable is an electro-acoustic music instrument with a tabletop Tangible User Interface that has been developed within the Music Technology Group at the Universitat Pompeu Fabra in Barcelona, Spain by Sergi Jordà, Martin Kaltenbrunner, Günter Geiger and Marcos Alonso.
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[edit] Basic operation
The reacTable is a round translucent table, used in a darkened room, and appears as a backlit display. By placing blocks called tangibles on the table, and interfacing with the visual display via the tangibles or by fingertips, a virtual modular synthesizer is operated, creating music or sound effects.
[edit] Tangibles
There are various types of tangibles, meaning that they can represent different modules of an analog sythesizer. Audio frequency VCOs, LFOs, VCFs, and sequencers are some of the commonly used tangibles. There is also a tangible called radar which is a periodic trigger that affects other modules, and a tangible that limits a VCO to notes of a musical scale.
[edit] Using tangibles with the display
The table itself is the display. As a tangible is placed on the table, various animated symbols appear, such as waveforms, circles, circular grids, or sweeping lines. Some symbols merely show what the particular tangible is doing, others can be used by fingertip to control the respective module.
[edit] Example of operation
If a VCO tangible is placed on the table, a VCO module is added to the virtual synthesizer. In the display, a waveform will appear between the tangible and the "ouput" (a bright spot at the center of the table), and a circle appears around the tangible which allows fingertip control of the amplitude of the wavform. Additionally, in this example the tangible can be rotated by hand to change the frequency.
Placing a filter tangible between the VCO and the ouput causes the VCO's waveform to "connect" to the filter, and the filter waveform to "connect" to the output. If an LFO tangible is placed near the VCO, a waveform will then appear "connecting" those two, and the LFO will modulate the VCO.
[edit] Structure
The reacTable's main user interface consists of a translucent table. Underneath the table is situated a DV video camera, aimed at the underside of the table and inputing video to a personal computer. There is also a video projector under the table, also connected to the computer, projecting video onto the underside of the table top that can be seen from the upper side as well.
Placed onto the table are the tangibles, that have fiducials attached to their underside which are seen through the table by the camera. These fiducials are basically printed black and white images, comprised of circles and dots in varying patterns, optimized for use by reacTIVision. reacTIVision then uses the fiducials to understand the function of a particular tangible.
Most of the tangibles are flat, with one fiducial on the underside. Some other tangibles are cubes, with fiducials attached to several sides, allowing those tangibles to serve mutliple functions.
[edit] reacTIVision
The video received from the video camera into the computer is processed by open-source computer vision software called reacTIVision originaly developed by Ross Bencina and Martin Kaltenbrunner. reacTIVision detects cartesian and rotational placement of fiducials in video images, then outputs OpenSound Control messages for music synthesizer software, either using MIDI or a specially designed packet based network protocol TUIO. reacTivision also tracks fingertip placement.
reacTIVision also communicates to the TUI software that outputs to the video projector.
[edit] Presentations
The reacTable has been presented and performed with at various festivals and conferences such as Ars Electronica, Sónar, NIME and SIGGRAPH.
[edit] External links
- reacTable project web site
- View Demo 1 [1]
- View Demo 2 [2]
