The Linkage Computer

This is my final project for 6.849: Geometric Folding Algorithms by Prof. Erik Demaine, the happiest genius of the world.

In fact I prefer to call it ‘the origami class’, which sounds more obscure to my friends. And complex, curving origami was indeed what I expected myself to do at the beginning. Well, the field turned out to be much broader and even more interesting (absolutely an understatement).

Anyway one day we were introduced to Kemp’s Universality Theorem, which says ‘there is a linkage that signs your name’. In proving that Kemp invented 3 gadgets: multiplicator, additor and translator, which perform arithmetic operations on any input angle. Then the idea came to me that if we can design gadgets that perform boolean operations, we can build a computer from just hinged bars.

I always had a thing for mechanical computers. The article that talks about the rope-and-pulley computer by Apraphulians was my all-time favorite of Scientific Americans. This project might be a little nerdy, but who knows — mechanical logic gates do make sense on nanoscale and in extreme environments like outer space.

Here is how I represent bits with bars. Note that each bar is constrained to rotate in half plane so I gain a nice ‘black box’ feature where the implementation of one gadget does not disrupt the rest of the machine.

Here are the logic gates: translator (moving a logic state across space), invertor (X -> not X), AND gate / OR gate (they are mirrored image of each other). Watch the video to see how they work.

Using the above gadgets I will be able to build a full adder (A, B, Cin as input and S, Cout as output). I’ve made a simple simulation with Processing. Click the input bars to switch states:

The models I constructed use wood sticks and rivets. I also proposed another way of building the gadgets — cut and fold them from one piece of flat material. It would be awesome to cut a whole mechanical computer out of one piece of thin metal, roll it and take it with you to a place with no electricity and do some crazy computation.

I’ll be continuing this project during the winter break. Many thanks to Erik & Martin Demaine and Tomohiro Tachi. It’s been so cool!

Tools used: AutoCAD, Processing

Redrawing the Map of Great Britain from a Network of Human Interactions

This paper has been published on PLoS ONE: full text

Do regional boundaries defined by governments respect the natural way that people interact across space? The URB team of SENSEable City Lab analyzed 12 billion anonymized landline calls in Great Britain to illustrate the true connections between places. The strength of connection is defined by the frequency and period of phone calls. It is revealed that people tend to communicate with those that are geographically close to them. Therefore, it is possible to identify clusters of connections as regional groups. It is fun to compare these new boundaries with existing ones and see how much people really love each other.

The visualization challenge here is the extra dense connections. An ideal vis solution should show clearer and finer pattern as data accumulates, not the opposite. Mauro Martino worked with the team from the beginning and derived the primary concept. I hopped on board later and finished with the final video to elaborate the whole idea. Processing is not able to handle this scale of objects (especially in animation) so a lot of pre-processing was done exclusively for each scene.

For those who cannot use YouTube, click this instead:


The research has also been covered by BBC and The Economist.

Collaborators in visualization: Mauro Martino, Francesco Calabrese
Tools used: Processing, R, Premiere

A Very Supernatural Map of United States

Uh… This is purely out of boredom. In welcome of the Season 6 of CW show Supernatural, I took a look at the path Sam and Dean have traveled. Guess which state hosted the most monsters?

Congratulations to Illinois! Then there goes South Dakota, Nebraska, Kansas, Pennsylvania, Ohio, Iowa, Indiana, Colorado, Missouri, Wisconsin, Oklahoma, Minnesota and California. The supernatural communities, be them spirits, creatures, mutants, psychics, witches, demons, angels or gods, definitely share taste in choosing playgrounds.

Click here to play with the interactive map:

I’m aware that there are a few fictional towns in the show. Coordinates are selected from the first result returned by Google Maps, so, if a circle falsely falls on your neighborhood, don’t panic! Corrections welcomed.

I am also aware that my lines between cities show shortcuts rather than actual trips. But you see, the brothers don’t always drive; they travel in time, in dream, in spirit forms; they have been zapped here and there by angels, demons and god himself. No such data is available as far as I know. Though I’d love to, watching the 5 seasons all over again is not in my short-term plan.

Data source: The Supernatural Wiki, Google Maps
Tools used: Google Maps API

The Slow Glass I

This is a project for a Media Lab class: New Paradigms for Human-Computer Interaction by Pattie Maes and Hiroshi Ishii. Slow glass was imagined by Bob Shaw in the science-fiction story The Light of other Days. Light travels very slowly in this material so that it takes months or even years for people to see what had been on the other side.

We consider the slow glass as an architectural element that provides a window into another space/time. It changes people’s perception of the surroundings. We tried to make an elegant implementation for the concept. The screen is located in the lobby of the new Media Lab building. One camera captures sequential images of the lobby and tracks the coordinates of people using background subtraction. Another set of cameras on the back of the screen records a panorama of the lobby. Video is played back, a few hours later, according to the relative positioning between a person and the screen. From a user’s perspective, the screen is like transparent, only that through it he sees the past.

The tracking system, powered by OpenCV:

A diagram of perspective simulation:

A video of the concept and the first prototype that we presented in the class review. We are currently working on making it a permanent installation in the Media Lab building:

Tools used: Open Frameworks, OpenCV, iMovie
Collaborator: Polychronis Ypodimatopoulos, Daniel Rosenburg

Map of Paris: Visualizing Urban Transportation

Update: If you are interested in isochronic maps, I have more detailed explaination of the process in my graduate thesis Seeing Differently: Cartography for Subjective Maps Based on Dynamic Urban Data, and the source code (Processing) is on GitHub.

What is your mental map of a city? I bet it’s not measured in miles. This project is part of my work in the SENSEable City’s workshop this semester. In these distorted maps of Paris, the distance between a spot and the city center is not proportional to their geographical distance, but the cost taken to get there.

Standard map vs. driving time map of Paris: the city center expands from congestion, and the edge is denser.

Comparing the isochronic map of Paris under different transportation modes: (unit: minutes, click to zoom in)

Think driving is better? However, if we map the city using carbon footprint as distance: (unit: kg CO2, click to zoom in)

In the workshop I proposed an alternative to Google Maps on smartphone map services. I call it an isogreenic map. This would have a psychological influence on the user when he decides which transportation makes the trip easier:

Made with Processing.
Vector map:
Connection data: Google Directions,

A demo video that shows how the transformation works: