Growing, Raining Tree stands inside a 20-foot-wide pool of water. The tree form is made of hand-shaped and milled aluminum with silicon skin and joints. The trunk and limbs house a wide and coordinated array of pneumatic, hydraulic, mechanical and computational components. These components have systems which extend various lengths along the limbs of the Tree, some to the very tips of the branches.

The movements of the Tree are programmed sequences of pneumatic and hydraulic responses, triggered by information gathered by the Tree’s computer vision system. The Tree’s vision system detects and locates movements along the perimeter of the pool. Once a movement is detected, the Tree is programmed to initiate a sequence of limb movements with the location of the detected motion as its focus. Computer-controlled pneumatic cylinders provide the motion for the Tree’s limbs, and computer-controlled pneumatic valves regulate the rhythmic dripping from the tips of the Tree’s branches. The computers and compressor equipment required for the Tree to function are located in other parts of the Museum.

The Tree’s pool water is pumped out a drain beneath the trunk and is replenished by the drops of water the Tree releases in response to the presence of visitors.

ARW can monitor the Tree over the internet with a camera similar to the one used in its vision system. Via the internet, ARW can also introduce new behaviors and activate the Tree’s movements for the purposes of testing and presentation.

Other Public Installations

Growing, Raining Tree is one of a number of permanent and long-term, public installations created by Amorphic Robot Works. Other works include Fœtus to Man, a outdoor clock for the city of Lille, France depicting the stages of the human life-cycle, and Urge to Stand, a popular fifteen-foot interactive sculpture in San Francisco’s Yerba Buena Gardens.

In Urge to Stand, when a person of at least 100 pounds sits on a bench facing the globe, the kinetic element of the sculpture is activated. As the bench slowly lowers, it engages a large underground lever which activates a series of link rods driving the counterweighted figure’s movement. When the observer on the bench sits, the figure on the globe also sits. When the observer stands, the figure slowly rises.

MacMurtrie has created a much simpler version of the Tree in Brooklyn, New York. This Water Tree takes the form of a public fountain, dropping water from its limbs when they become heavy with water. It has been very popular with its visitors.

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