> Motivation
> Example Movie
> Comment
> Conclusion
> Related Experiments
> Setup

Performance Photo


> Top



How can we write a motion on the screen? Assuming that perceiving a motion involves our memory (because we are constructing a motion of an object in our minds by remembering it's recent positions), we can give additional hints to the perception by displaying the last positions of the object. Displaying a three dimensional object at all it's recent positions would result in a complex sculpture. For simplicity we reduce the information and focus just on the relation between two points, e.g. the hands. Moving a point in space results in a line. Likewise moving a line in space creates a plane or band. The length of this band corresponds to the extension of the memory in time. This band metaphorically is writing the last seconds of motion on the screen.


> Top


Example Movie

Stage View
Computer Image
An imaginary line between the two hands leaves a motion trace. The distance between the two hands determines the width of the transparent trace. Several times the dancer decides to freeze the image of the trace (by using the RF button in his hand), which is shown as a slowly turning object in space. This object is used as a feedback informing the improvisation, as well as the movement of the body and the resulting next trace.


> Top



What we discovered with this set-up is that the trace has a visual quality that has a strong potential to be used as feedback and inspiration for the dancer's improvisation. The objects that are carved into the space have a spatial complexity that can be read and re-translated into movement. Also the transparent surface of the trace has an airy and light quality that seems to be moving within itself. The fact that the trace can be stopped and kept as a frozen, yet rotating record of the past movement, gives time to observe and interpret the 3-dimensionality of the object the trace forms.

This trace holds a certain grace; we were reminded of fabric or silk, thrown into the space. We were also thinking about architecture and how the trace forms an ever-changing 3-dimensional object. The movement of the dancer can easily be corresponded to the projected trace. The version you can see in the is different: first you see only Thomas move, then there is a short time where you can observe both him and the trace he is creating. Later the lights on Thomas fade out and all that is left to the observer's eye is the trace alone. The human body might be invisible but it is nevertheless present in its movement trace.

In this set-up the projected trace translates the paths that the hands travel. It amplifies the whole dance sequence by making visible the history of what has just taken place. We talked and agreed about this word amplifies because the trace enlarges the awareness of this relationship of the hands, how they move through space, and is left standing there for a while so you can really savor the intricacies of it's curves and inclinations.


> Top



This setup utilizes several correlations between the dancer's motion and the resulting image: the global location, the relative location of depicted limbs and the speed of these limbs. Since these properties are mapped directly (locations to locations and speed to texture shifting speed), they are preserving their perceptual quality in the image and thus are intuitively legible. The continuous trace allows the eye to pace off the past motion triggering past images from memory. Because of the direct mapping it has even properties of a rudimentary notation mechanism.

The length of the recording is freely adjustable, ranging from showing just the present motion to covering a long motion sequence. This can be even dynamically changed during a performance.


> Top


Related Experiments


> Top




  • Graphics PC
  • Projector
  • Polhemus tracking system: 2 Sensors


  • The two Sensors are attached to the dancer's hands. The computer reads the realtime data from the sensors and stores their recent positions. A visual plane is constructed out of these positions by connecting the line segments defined by each pair of positions in a chronological order. A noise texture is applied to the resulting geometry in order to give additional visual information on the surface of the plane indicating the stretching of the segments. The left edge of the texture image is mapped to the most recent recorded line, the right edge of the image is mapped to the least recent recorded line. All in-between lines are mapped in equal spaced steps. Thus the texture image floats with the movement and stretches with fast movements.
    The Technical Screenshot below shows the sensors as green wireframe spheres.


Technical Setup

Spatial Setup

Technical Screenshot

> Top