A series of abstract three-dimensional branching forms created through a custom-designed computational model based on Lindenmayer system theory. Visitors may explore and display each form through a simple touch-sensitive interface.

The six modules.

The interaction demo.
(Quicktime, broadband)


The primal creative urge to replicate nature is shared by many artists, and gets a big boost with every cycle of new digital technology, and with every improvement in mathematical modelling of living systems. Digital representations of reality are asymptotically approaching life itself. Personally we are both fascinated by and conflicted about this phenomenon. If we love to watch growth occur, why are we generating real-time 3D models rather than shooting old-fashioned time-lapse films of plants growing? Impatience? No, frankly, we're infected by two classic human addictions, the need to control, and the urge to discover. Replicating natural forms is interesting, but not as fascinating as creating new ones — forms that seem familiar, yet are unique.

Our intent in this work is to present aesthetically pleasing, interesting forms that loosely mimic natural branching structures but are expressed in purely abstract geometric terms — a contrast of the natural and the artificial. We also wish to encourage easy, low-learning-curve exploration and intervention, which will be rewarded with new views and new forms.

Giving gallery visitors interactive control over generative imagery can be risky if the artist does not define some boundaries. In our case we have chosen to pre-select the model systems to be presented in the work. Based on manipulation and experimentation with the code structure, rule base, and parameter settings, we have chosen a small collection of those model systems that we found most interesting. Visitor control is confined to rotation of each form to facilitate inspection, and triggering of the “cringing” faux-death of the form that results in a new form being revealed. In this version of the Variations, six forms are revealed in sequence. The rule base and parameters of each form are interpreted and displayed in real-time, through a C++ application using OpenGL.

Tufts of live grass are used as the interface device, installation conditions permitting. We like the tactile effect, ease of use (simply touching), and appearance of this approach. The non-technical, organic nature of the live plants could also be seen as a parody of the digital non-life forms we are creating (or vice-versa). These neatly-trimmed plantings, placed before the screen, will invite visitors to play. Feedback from touching the grass is instantaneous: the visual form immediately changes, and a delicate tonal sound also is heard through a hidden speaker.

Visitors approach a pedestal topped with three neatly trimmed tufts of grass (two rectangles and a circle). On the wall behind the pedestal is a wide screen flat panel display mounted vertically. (In the larger version of this piece, the wall 12 feet in front of the pedestal displays a projected image, at least 6' x 8'.)

The image is a jointed branching structure composed of many short polygonal segments, slowly rotating in 3-space. The structure may be in the process of growing branches and generating end-points, or may be fully formed, depending on how long ago other visitors have been present.

If visitors do not touch the grass within one minute, the rotating form will begin to contract toward the center of the space and lose some of its saturation. Any touch to any of the three grass segments will cause the form to “un-cringe” and recover its full color and size.

Visitors may touch: •The left grass rectangle, which causes the form to rotate in a positive direction around the Y (up) axis. •The right grass rectangle, which causes the form to rotate in a negative direction. •The center, circular grass segment, which causes the form to suddenly collapse and desaturatue, and disappear. A new form then begins to grow.

The new form may be fully grown in less than a minute, or may take several minutes to fully develop. All the while it will be slowly rotating and gently flexing. Visitors may interact at any time.


Professor Peter Mackey (MFA, Cinema, University of Southern California) is on the full-time faculty in the Department of Digital Arts (formerly Computer Graphics and Interactive Media) at Pratt Institute in Brooklyn, NY. He has been teaching interactive media for twelve years, and producing multimedia projects for nearly 30 years.

Matthew Mackey has an MS in Computer Science from the University of Southern California and is currently Senior Software Engineer for The Database Factory in Studio City, CA.

Peter previously collaborated on Matthew's Reverse Psycholotron last seen at Burning Man 2005.


An Introduction to Lindenmayer Systems by Gabriela Ochoa.

The Algorithmic Beauty of Plants by Przemyslaw Prusinkiewicz and Aristid Lindenmayer. The primary source for this topic, richly detailed.

Polygon Gardens by Jerry McManus, a Shockwave 3D implementation.