Sunday, February 17, 2008

Halftone Stencils

Almost all stencil graffiti operates on the principle of separating thresholding colors. Last summer, on the side of a Roman business, I saw another approach: line engraving. It made me wonder, "what other techniques have yet to be explored with stencils?"

The first one I've imagined is halftone stenciling. Ideally, there would be some cheap way to create a halftone stencil "printer" able to cut many small holes of variable size from card/paper. I can only imagine it involving some sort of spiral/conical head where variable depths correspond to variable diameters. With four layers we could reproduce images using a CMYK separation model. A quick prototype might be done with Illustrator and laser cutter.

Surprisingly, at least two people have endeavored to produce these by hand. One took two weeks, the other used paper instead of card ("no fucking way am i cutting a 1000's holes on card n lose all feeling in my index finger for 3weeks").

Update: it works. If you have access to a laser cutter, you can make your own.

Truly DIY Bullet Time

The winner of Instructables' Laser Cutter Contest was "DIY Bullet Time". Unfortunately, in this case DIY means "only costs $5000-$8000 and takes just two days".

The difficulty of capturing bullet time images is that it requires a number of simultaneous perspectives, and each perspective implies a light capturing mechanism and storage device. In this case, each perspective is filled by a separate camera.

What if we combined the perspectives and captured them in parallel? For example: set up a network of mirrors and lenses to redirect the light from each perspective into a matrix/2D-grid that is projected onto the lens of a single camera. The main limitation of this approach would be that certain configurations are much easier to construct than others.

Another possibility: use a microcontroller to process the images from multiple cheap webcams and send them via USB to a computer for storage. USB runs at 480Mbits/s, or 16Mbits/frame at 30 fps (more likely 32Mbits/frame since cheap webcams are still in the 15 fps range). This allows for up to 16 uncompressed 1 megapixel (640x480 pixel) frames in parallel. The number of perspectives is probably more limited by the speed of the microcontroller than the USB speed. Total price would be two orders of magnitude lower than the Instructable, in the range of $120 if 16 cameras at $6 each and some electronics coming to less than $20 are used.


I'd like to see a collection of videos on YouTube taking advantage of the potential title/content dichotomy allowed by the format. For example, videos titled "Tsunami" displaying a small, regular wave. "Earthquake" showing an unexpected misstep in someone's stride. "Pileup" showing a minor bumper bender. It would be ideal if the scenario presented had the potential to develop into the titular situation, but refused to manifest.

The Beat of the World

Watching the World Clock, you can almost feel the pulse of certain statistics. It'd be interesting to make a mixtape that kept one of these statistics as the tempo throughout the entire mix. Imagine a dance party where every beat corresponds to a death. Or a birth. Or a new car/computer/bicycle. Perhaps these dance parties should be held in pairs, and which dance you were doing wouldn't be revealed until the dance was over. A chance for meditation.

Arduino as an ADC/DAC

The most recent Arduino runs at 16MHz, and can sample analog signals every 100 microseconds (about 10KHz) at 8 bit resolution. This is a reasonable audio sampling resolution, allowing us to capture and reproduce at least 5KHz, with processing time left over for doing DSP. In short, we could run an Arduino off a 9V battery and stick it in a guitar pedal.

An alternative use involving DAC would involve connecting via serial to the Arduino at a quick baud (say, 115200) and using each of the 6 PWM "analog outputs" as DACs, yielding 19200 baud per channel. With 8 bit audio, that's a 2.4KHz sample rate, or 4.8KHz for 4 bit audio. That is, we could use the Arduino to route low resolution 5.1 surround sound.

More on some of these possibilities here.

The TSA is Everywhere

The Transportation Security Administration oversees all checked baggage traveling through American airports. When they check bags they leave little notes behind.

I'd like to make tons of copies of these notes and leave them all around the country in unexpected places. Or, maybe it would be best to pick one location (e.g., a university) and really inundate that location.