| The U. T. Touch-Sensitive Dance Floor and MIDI Controller | |
|
Pinkston, Kerkhoff, & McQuilken |
|
|
|
|
| ABSTRACT | |
| A prototype MIDI Dance Surface has been developed which is capable of transmitting precise position coordinates, velocity and pressure information in the form of standard MIDI messages. The surface consists of a large number of Force Sensing Resistors (FSRs) which are attached to heavy duty plastic sheeting and covered with polyethylene foam. The sheets may either be placed on top of or beneath a standard Marley Dance floor. The FSRs are typically arranged in a grid with 16 columns (left to right) and 4 rows (front to back), which results in a 16' square dance surface with 64 1' x 4' velocity and pressure sensitive regions, each of which is assigned a separate input channel of a Voltage to MIDI Interface Box which has 64 analog inputs, plus MIDI Out. The MIDI Box incorporates a Motorola MC68HC11 microprocessor and can be programmed to convert input/output analog signals to/from any desired MIDI messages, on multiple MIDI channels. Hence, used in conjunction with an "intelligent" external MIDI processing system, it is ideal for use in interactive dance compositions in which one or more dancers can affect both the music and lighting by the nature of their movements and by their precise position(s) on the surface. | |
|
Background |
|
| In recent years, numerous systems have been devised for the purpose of capturing the movements of dancers and converting them into signals which can be used to control various aspects of a musical/theatrical performance. The technological means which have been utilized are many and varied, ranging in complexity from simple on/off triggers placed on the floor, to highly sophisticated systems incorporating ultrasound, radio, and real-time visual analysis. All of these systems, however, tend to reflect one or the other of two fundamentally different approaches: One approach involves what may be referred to as "passive control." It is based on the ideal that dancers should be completely free to move normally, that it is the responsibility of the system to detect their movements accurately and respond to them in an appropriate manner. Dancers using such a system would not necessarily have to be conscious of how their gestures were being used for control. Consequently, there should be no artificial restrictions on the creativity of either the choreographer or the performers. The other approach involves "active control," and it requires that the dancers be very aware of the specific effects of their movements. The ideal here is that a system should provide dancers with very precise control, allowing them to play music and/or produce sounds directly through highly specific, conscious actions. Once the dancers have learned to manipulate such a system effectively, they should be able to "play it" like a musical instrument, with much greater sensitivity and expressiveness than they could with a passive system. There are technical and aesthetic pros and cons to each approach, which are beyond the scope of this paper. The University of Texas MIDI Dance Floor was designed to support both of these approaches, but in practice, the most musically interesting uses of the system have involved active control by individual dancers. | |
|
The University of Texas MIDI Dance Floor |
|
| The MIDI Dance Floor is an experimental prototype for a system capable of being used for both active control and passive sensing, which would not require the dancers to wear or carry any special materials, and which would not be prohibitively expensive to produce. It utilizes Force Sensing Resistors (FSRs) from Interlink Corporation, which are made of a thin, flexible, and relatively strong material and are manufactured in a variety of shapes and sizes. The FSRs are very sensitive and produce a useful range of resistance which varies in inverse proportion to the amount of force applied to them. We employed a total of 128 24" FSRs, affixed to four 16' x 4' strips of heavy duty plastic sheeting, 32 per strip. 16 pairs of FSRs, wired in parallel, were attached to the plastic with contact cement and laid out as shown below. | |
|
FSR Arrangement |
|
|
|
|
| This arrangement was adopted to cover the maximum area and in order to place the solder tabs at the center of each section for protection. Wiring pairs of FSRs in parallel effectively created 16 4-foot long FSRs, which halved the number of A/D channels required by the interface and still provided a reasonably dense number of sensors per square foot. The FSRs were then covered with a thin layer of polyethlyene foam, both to protect them from direct impact and to help spread the force horizontally. The sections were intended to be arranged side by side, forming a 16 foot square dance area, and to be placed beneath a standard Marley-type dance floor, which could then be marked with glow tape to show the location of the sensors, if desired. A 64-channel Voltage/MIDI interface box was designed and built by Mark McQuilken, using a Motorola MC68HC11 microprocessor. The interface supplies each FSR with a small voltage, which varies whenever the resistance does. The 'HC11's control program tracks the signals and produces both a MIDI Continuous Controller message and a MIDI Note-On/Note-off pair for each FSR. Note On/Off messages are generated whenever the voltage passes a predetermined threshold. Higher level processing of the MIDI messages is performed on a Macintosh computer using control programs written in MAX. The following diagram shows a typical performance setup: | |
|
Basic Performance System Diagram |
|
|
|
|
| Although the diagram above shows the four floor sections arranged side by side, forming a square roughly 16' by 16', to date, the system has never actually been used this way in performance. Instead, various alternative arrangements of the floor sections have been employed, including lining up several sections end-to-end across the front of the stage, diagonal configurations, and a T-shaped arrangement, with one section across the stage front and another placed perpendicularly, coming down the center. The primary reason for these alternative arrangements is to leave large areas of the stage uncovered, and only to place floor sections where they need to be for the choreography, so that the dancers are usually not touching on the MIDI floor and only move onto it when they are required to trigger or shape a specific musical event.. | |
|
MIDI Controller Interface Block Diagram |
|
|
|
|
|
The figure above shows a simplified block diagram of the MIDI Dance Floor's Analog/Digital & MIDI interface, which was designed and built by Mark McQuilken. For more information on Mark and his current research interests, see http://www.fmraudio.com. Aspects of the hardware design and portions of the MC68HC11 control program were contributed by Jim Kerkhoff, Assistant Dean for Information Technology and Director of the Center for Advanced Studies in the Arts, College of Fine Arts, The University of Texas at Austin. For more information on Jim and CASA, see http://www.utexas.edu/cofa/casa. |
|
| Project and Performance History | |
| The idea for The University of Texas MIDI Dance Floor was first proposed to Russell Pinkston in 1994 by Yacov Sharir, founder and artistic director of the Sharir Dance Company, Austin, Texas, who expressed interest in having a "touch-sensitive dance floor" made for him. Pinkston then collaborated with Jim Kerkhoff and Mark McQuilken in the design and building of the floor, and subsequently wrote all the MAX programs used in controlling the system in performance. Since its completion, the U. T. MIDI dance floor has been used in four interactive dance compositions with music by Pinkston: Dervish Sketches (choreographed and danced by Yacov Sharir & Jose Bustamante), Memory of Absence (written for the Sharir Dance Company, choreographed and danced by Jose Bustamante); All Round Me (written for the Sharir Dance Company in collaboration with choreographer/dancer Andrea Beckham and artist John Christensen), and Song for the Living/Dance for the Dead (a version of All Round Me choreographed by Mata Saka, with videos by Anita Pantin). Song for the Living/Dance for the Dead was performed at the Merce Cunningham Dance Studio by dancers from the Merce Cunningham School) during the 1999 Columbia Interactive Arts Festival. See the following link for more information: http://www.music.columbia.edu/fest99/events/all_round.html | |
