Wednesday, August 24, 2011

We ♥ : Laser Cut Generative Butterfly Installation

In the summer of 2007, The Barbarian Group was invited to participate in the exhibit Interactivity at the McLeod Residence – a gallery in Seattle, Wa. The Barbarians developed three pieces: the McLeod Mirror, Reflection 1: See Yourself in Others, a series of prints known as The Magnetic Structure Prints, and this project, Biomimetic Butterflies. The Butterflies were the centerpiece of the show, an installation taking up an entire room.
The Butterflies were a result of a cross country collaboration between Barbarians located in San Francisco, Boston, New York, and Los Angeles. The pedestals were constructed by Vince, a fabricator in Seattle


Our goal was to create mechanical creatures which would respond to observers by flapping their wings. Their motion is achieved using a combination of stepper motors, rare earth magnets, some custom circuitry and a Mac Mini driving the whole thing using input from a video camera. The Butterflies’ wings are created using designs which were laser cut into paper.
paper cutout detail
The Butterfly wings are made of laser cut, heavyweight drawing paper. After laser cutting, and some clean-up with an X-Acto knife, the wings are glued to a small piece of cotton to form a simple and delicate hinge. Using lightweight fabric keeps the overall look clean and creates a hinge with much less resistance than a more standard mechanical hinge. Each wing is fitted with two pairs of neodymium magnets by sandwiching the wing paper between each pair, making sure that the polarity on all magnets is consistent. To keep the Butterfly in place, we pin it to the mounting board with black insect mounting pins.
The fact that we need to laser cut these designs presents an interesting creative constraint. It means that the patterns have to obey the basic rules of stenciling - we cannot allow any “islands” or the wings would fall apart. In addition to each laser cut variation, we generate an additional 14 designs per species using their respective algorithms, which are printed in pairs.
The wings are articulated by moving a large neodymium magnet oriented so that it has the opposite polarity of the magnets on the wings. For example if the magnets on the wings all have the south pole facing down, the large magnet will have south facing up. So when the large magnet is moved close to the wings, the magnets on the wings are repelled causing them to close. To move the magnet, it is mounted to a servo motor using a 2" plastic drum. The servo faces perpendicular to the central vertical axis of the Butterfly’s body. The magnet is mounted on the edge of the drum so rotating the servo causes the magnet to move away from the Butterfly, which in turn lessens its effect on the wing.
All servos are connected to a single computer using an Arduino board. This opens the door for any number of possible control inputs for the Butterflies. For the installation at the McLeod Residence, we used a webcam mounted at the back of the room to look for movement in front of each butterfly. As visitors walk closer to get a better view, the Butterfly in the pedestal they approach begins to flap its wings. Since the Butterflies respond to movement, not presence, they soon settle down as the viewer stands still while watching, only to briefly flutter again when he or she walks away.
The pedestals are hollow so they can accommodate stepper motors and much larger rare-earth magnets. The stepper motor can be controlled via Processing and Arduino so that it can rotate the large magnet up towards the top of the pedestal. The polarity of the magnets on the Butterfly is such that the large magnet can push the smaller magnets away. Since the Butterfly wings are pinned to the pedestal, they take on the appearance of flapping.

1 comment:

  1. lovely blog!

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