Figure: (a) User dancing with her colored shadow in DanceSpace (b) Dancing shadow generated by the user in DanceSpace
Closely related to the gesture-based interface mapping discussed in Section 3.3, the conductor-style interface mapping of DanceSpace also uses a form of predefined gesture language. The important difference lies in the design of that language. The gesture-language of NetSpace is very rigid. Specific gesture sequences generate specific reactions, and conversely, failures in the tracking and classification of the user's actions can result in inappropriate actions by the system. The conductor mapping results in a much more fluid interface. The user can certainly try to explore the control space, learn it, and use it as a rigid language, but the system is designed to produce constructive, interesting results when this doesn't happen. The interactions the user has with this system are arguably more interesting when the user doesn't know the details of the mapping.
DanceSpace is an interactive performance space where both professional and non-professional dancers can generate music and graphics through their body movements (See Figure 10).
The music begins with a richly-textured melodic base tune which plays in the background for the duration of the performance. As the dancer enters the space, a number of virtual musical instruments are invisibly attached to their body. The dancer then uses their body movements to magically generate an improvisational theme above the background track.
The dancer has a cello in their right hand, vibes on their left hand, and bells and drums attached to their feet. The dancer's head works as the volume knob, bringing down the sound as they move closer to the ground. The distance from the dancer's hands to the ground is mapped to the pitch of the note played by the musical instruments attached to the hands. Therefore a higher note will be played when the hands are above the performer's head and a lower note when they are near their waist. Both hands' musical instruments are played in a continuous mode (i.e., to get from a lower to a higher note the performer will have to play all the intermediate notes). The bells and the drums are on the contrary ``one shot'' musical instruments. When the performer raises their feet more than 15 inches off the ground then either of the bells/drums are triggered, according to which foot is raised.
The music that is generated varies widely among different users of the interactive space. Nevertheless all the music shares the same pleasant rhythm established by the underlying, ambient tune, and a style the ranges from ``pentatonic'' to ``fusion'' or ``space'' music.
As the dancer moves, their body leaves a multicolored trail across the large wall screen that comprises one side of the performance space.
The graphics is generated by drawing two bezier curves to abstractly represent the dancer's body. The first curve is drawn through coordinates representing their left foot, head, and right foot. The second curve is drawn through coordinates representing their left hand, center of their body, and right hand. Small 3-D spheres are also drawn to map onto hands, feet, head and center of the body of the performer, both for a reference for the dancer and to accentuate the stylized representation of the body on the screen. The multicolored trail is intended to represent the dancer's shadow that follows them around during the performance. The shadow has a variable memory of the number of trails left by the dancer's body. Hence if the shadow has a long memory of trails (more than thirty) the dancer can paint more complex abstract figures on the screen.
The choreography of the piece can then vary according to which one of the elements of the interactive space the choreographer decides to privilege. In one case the dancer might concentrate on generating the desired musical effect; in another case or in another moment of the performance, the dancer may want to concentrate on the graphics - i.e. painting with the body - or finally the dancer might just focus on the dance itself and let DanceSpace generate the accompanying graphics and music.
The philosophy underlying DanceSpace is inspired by Merce Cunningham's approach to dance and choreography . The idea is that dance and movement should be designed independently of music and that music should be subordinate to movement and may be composed later for a piece as a musical score is done for film. When concentrating on music, more than dance, DanceSpace can be thought of as a ``hyperinstrument''. Hyperinstruments are musical instruments primarily invented for non-musical-educated people who nevertheless wish to express themselves through music. The computer that drives the instruments adds the basic layer of ``musical knowledge'' needed to generate a musical piece. Moreover we have thought of DanceSpace as a tool for a dancer/mime to act as a street performer who has a number of musical instruments attached to their body. The advantage of DanceSpace over the latter is that the user is unencumbered and wireless and can be more expressive in other media as well (its own body or computer graphics). The disadvantage is that DanceSpace is mainly a music improvising system and it is therefore difficult to use it to reproduce well known musical tunes.
Future improvements to DanceSpace include having a number of different background tunes and instruments available for the dancer to use within the same performance. Another important addition will also allow the user to adjust the music's rhythm to their rhythm of movement. We would also like the color of the dancer's graphical shadow to match an expressive or emotional pattern in the dance and become an active element in the choreography of the piece.
We see DanceSpace as a possible installation for indoor public places, as for example airports, where people usually spend long hours waiting, or interactive museums and galleries. DanceSpace could also become part of a performance space, allowing a dancer to play with their own shadow and generate customized music for every performance.