"Body Movies - Relational Architecture No. 6" is an installation demanding public access for the interaction. Portraits are projected on a building wall but can only appear inside the projected shadows of local passers-by. Without shadows the portraits are completely washed out by strong light sources. A camera-based tracking system monitors the location of the shadows on real time, and when the shadows match all the portraits in a given scene, the control computer issues an automatic command to change the scene to the next set of portraits.

“Body Movies“ was the sixth in the series of installations in public space that Rafael Lozano-Hemmer has designed for cities in Europe and America. These interactive interventions in Madrid, Linz, Graz, Mexico City and Havana have been exploring the intersection between new technologies, urban space, active participation and "alien memory". For the Cultural Capital of Europe Festival in Rotterdam, the V2 organization commissioned Lozano-Hemmer to develop a new piece.

From the 31st of August until the 23rd of September the Schouwburgplein square was transformed by the projection of huge interactive portraits on the façade of the Pathé Cinema building. Thousands of portraits taken on the streets of Rotterdam, Madrid, Mexico and Montreal were shown using robotically controlled projectors located around the square. However, the portraits only appeared inside the projected shadows of local passers-by, whose silhouettes measured between 2 to 22 metres high, depending on how far people were from the powerful light sources placed on the floor of the square.
When the Schouwburgplein was empty the portraits could not be seen, since the light sources on the floor completely washed them out with strong white light. As soon as people walked on the square, their shadows were projected and the portraits were revealed within them. A camera-based tracking system monitored the location of the shadows in real time, and when the shadows matched all the portraits in a given scene, the control computer issued an automatic command to change the scene to the next set of portraits. This way the people on the square were invited to embody different representational narratives. Up to 60 people took part at any given time, controlling 1,200 square metres of projections and creating a collective experience that nonetheless allowed discrete individual participation.

The shadow interface is a direct reference to Samuel van Hoogstraten's engraving „The Shadow Dance“ which appears in his „Inleiding tot de Hoge Schoole der Schilderkonst“. This engraving, made in Rotterdam in 1675, shows a minute source of light placed at ground level and the shadows of actors taking on demonic or angelic characteristics depending on their size. The optical devices deployed by Dutch masters of trompe l’oeil and anamorphosis are the starting point for a piece interested to investigate the crisis of urban self-representation. „Body Movies“ will transform the building of a cinema into a vehicle to study the distance between people and urban representation.

Technology

Three networked computers control the installation: a camera server, a video tracker, and a robotic controller cued by MIDI signals. The camera server is a self-contained Linux box that feeds video images to a PC over Ethernet 20 times per second. The camera has a wide-angle lens and it is pointed at the facade of the Pathé building. Custom-made software programmed in Delphi analyses the video detecting the edges of the shadows. The computer vision system determines if the shadows are covering portraits in the current scene. When a portrait is revealed, its hotspot turns white and remains activated for a few seconds. A wave file sound is also triggered to give feedback to participants in the square. VU meters in the interface show the status of each portrait and the degree of darkness over the hotspot.

When all the hotspots are activated, the PC sends a MIDI signal to the robotic controller to trigger a complete blackout followed by a new series of portraits in completely different locations. The PC is connected to the four xenon projectors by an RS485 serial connection. The library of images consists of over 1,200 portraits on durantrans frames each 15 x 15 cm and these rolled onto the robotic scrollers.

A video projection on the square shows the computer interface, beside a printed explanation in Dutch and English. Providing public access to the interface was a crucial part of the project.