Hansel & Gretel opened this month in New York. The collaboration between artist Ai Weiwei and architects Jacques Herzog and Pierre de Meuron is a noisy dystopian nightmare projected back to visitors and broadcast live to the internet.
The installation includes sobering military drone statistics that estimate between 6,300 and over 9,200 people have been killed by military drones.
The artists and technicians also explain the technology:
Every movement in the Drill Hall is tracked and recorded from above by a grid of 56 small computers with infrared (IR) cameras, each attached to a projector suspended on a truss system high above the gently sloping floor. To allow for better tracking in low light conditions we installed an array of floodlights which operate in the near infrared spectrum and are thus is invisible to the human eye. Each computer runs a tracking algorithm that compares a preprogrammed image of the floor to the real time camera feed, and subtracts away any redundancy until only the difference features remain. The moving person can thus be isolated, identified, and followed, which triggers a red rectangular outline and grid pattern to appear.
The IR image now overlaid with tracking data undergoes a series of visual transformations. The powerful computers are able to make adjustments in cropping, scaling, warping, shifting, rotation, exposure, brightness, and sharpness, all within milliseconds. Only then are the "real time" images sent to the projector. The entirety of the 215 x 145 foot Drill Hall floor is covered by a total projection surface of 12360 x 7850 pixels, with each pixel being approximately ⅕ of an inch.
• Hansel & Gretel (via Quartz)