Kinetic Rain

Context

In 2012, Changi Airport Group in Singapore commissioned the company ART+COM to build a sculpture that could be displayed in their newly renovated terminal. They requested that the sculpture’s theme relate to Singapore’s status as the “garden city.” The company decided on making a large kinetic sculpture consisting of brass raindrops that could form three-dimensional shapes. Many of these shapes invoke images of flight including a hot air balloon, a space shuttle, and a flying airplane. The sculpture cycles through these images in a fifteen minute “choreographed dance.”

The Mechanism

As a public art piece, Kinetic Rain functions mainly as a symbol for the airport and as a space for people to contemplate. Spectators can walk around the sculpture to get a different perspective as the raindrops move. ART+COM describes this movement as a “dialogue” in which “at times, the two parts move together in unison and other times they mirror, complement, or follow each other” (“Kinetic Rain, 2012” 1).  To achieve this “dialogue,” designers had to balance computation and mechanism. At the computational level, 3D models were designed and rendered. Then, using specially designed software these designs were spliced and converted into a series of positions and timing sequences that could be read by the servo motors controlling the drops. At the mechanical level, each raindrop was attached to its own servo motor which was designed such that the raindrop’s position could be controlled precisely. Combining these computational and mechanical systems allowed ARTCOM to easily render any complex 3D shape using the raindrops.

One of the problems that ART+COM encountered was getting the raindrops to move in unison without any jerky movements to maintain the illusion of free flowing rain. To achieve this illusion, the position of each drop is compared to a table of position values every 2ms. These position values are calculated by a spline algorithm which generates 100 intermediate positions so that the drop’s movements appear smoother. In addition, since each drop is controlled by a servo motor, its movements are within 1mm of the desired position. By combining these solutions together, the final installation moves gracefully, as if the drops are controlled together rather than individually.

Further information can be  here and here