A hanging plotter, also known as a polar plotter or polargraph, is a machine for drawing images on a vertical surface. It does so by using motors to control the length of two cords that form a V shape, supporting a pen where they meet. We’ve featured one on this blog before: Norbert “HomoFaciens” Heinz’s video is a wonderfully clear introduction to how a polargraph works and what you have to consider when you’re putting one together.
Today, we look at Inky Lines, by John Proudlock. With it, John is creating a series of captivating and beautiful pieces, and with his most recent work, each rendering of an image is unique.
An evolving project
The project isn’t new – John has been working on it for at least a couple of years – but it is constantly evolving. When we first spotted it, John had just implemented code to allow the plotter to produce mesmeric, spiralling patterns.
But we’re skipping ahead. Let’s go back to the beginning.
From pixels to motor movements
John starts by providing an image, usually no more than 100 pixels wide, to a Raspberry Pi. Custom software that he wrote evaluates the darkness of each pixel and selects a pattern of a suitable density to represent it.
The two cords supporting the plotter’s pen are wound around the shafts of two stepper motors, such that the movement of the motors controls the length of the cords: the program next calculates how much each motor must move in order to produce the pattern. The Raspberry Pi passes corresponding instructions to two motor circuits, which transform the signals to a higher voltage and pass them to the stepper motors. These turn by very precise amounts, winding or unwinding the cords and, very slowly, dragging the pen across the paper.
The earlier drawings that John made used a repeatable method to render image files as lines on paper. That is, if the machine drew the same image a number of times, each copy would be identical. More recently, though, he has been using a method that yields random movements of the pen:
The pen point is guided around the image, but moves to each new point entirely at random. Up close this looks like a chaotic squiggle, but from a distance of a couple of meters, the human eye (and brain) make order from the chaos and view an infinite number of shades and a smoother, less mechanical image.
This method means that no matter how many times the polargraph repeats the same image, each copy will be unique.
A gallery of work
Inky Lines’ website and its Instagram feed offer a collection of wonderful pieces John has drawn with his polargraph, and he discusses the different techniques and types of image that he is exploring.
They range from holiday photographs, processed to extract particular features and rendered in silhouette, to portraits, made with a single continuous line that can be several hundred metres long, to generative images spirograph images like those pictured above, created by an algorithm rather than rendered from a source image.
A year strongly defined by mixed success! Also, a lot of video games.
I ran three game jams, resulting in a total of 157 games existing that may not have otherwise, which is totally mindblowing?!
For GAMESMADEQUICK???, glip and I made NEONPHASE, a short little exploratory platformer. Honestly, I should give myself more credit for this and the rest of the LÖVE games I’ve based on the same codebase — I wove a physics engine (and everything else!) from scratch and it has held up remarkably well for a variety of different uses.
I successfully finished an HD version of Isaac’s Descent using my LÖVE engine, though it doesn’t have anything new over the original and I’ve only released it as a tech demo on Patreon.
For Strawberry Jam (NSFW!) we made fox flux (slightly NSFW!), which felt like a huge milestone: the first game where I made all the art! I mean, not counting Isaac’s Descent, which was for a very limited platform. It’s a pretty arbitrary milestone, yes, but it feels significant. I’ve been working on expanding the game into a longer and slightly less buggy experience, but the art is taking the longest by far. I must’ve spent weeks on player sprites alone.
We then set about working on Bolthaven, a sequel of sorts to NEONPHASE, and got decently far, and then abandond it. Oops.
We then started a cute little PICO-8 game, and forgot about it. Oops.
I was recruited to help with Chaos Composer, a more ambitious game glip started with someone else in Unity. I had to get used to Unity, and we squabbled a bit, but the game is finally about at the point where it’s “playable” and “maps” can be designed? It’s slightly on hold at the moment while we all finish up some other stuff, though.
We made a birthday game for two of our friends whose birthdays were very close together! Only they got to see it.
For Ludum Dare 38, we made Lunar Depot 38, a little “wave shooter” or whatever you call those? The AI is pretty rough, seeing as this was the first time I’d really made enemies and I had 72 hours to figure out how to do it, but I still think it’s pretty fun to play and I love the circular world.
I made Roguelike Simulator as an experiment with making something small and quick with a simple tool, and I had a lot of fun! I definitely want to do more stuff like this in the future.
And now we’re working on a game about Star Anise, my cat’s self-insert, which is looking to have more polish and depth than anything we’ve done so far! We’ve definitely come a long way in a year.
Somewhere along the line, I put out a call for a “potluck” project, where everyone would give me sprites of a given size without knowing what anyone else had contributed, and I would then make a game using only those sprites. Unfortunately, that stalled a few times: I tried using the Phaser JS library, but we didn’t get along; I tried LÖVE, but didn’t know where to go with the game; and then I decided to use this as an experiment with procedural generation, and didn’t get around to it. I still feel bad that everyone did work for me and I didn’t follow through, but I don’t know whether this will ever become a game.
veekun, alas, consumed months of my life. I finally got Sun and Moon loaded, but it took weeks of work since I was basically reinventing all the tooling we’d ever had from scratch, without even having most of that tooling available as a reference. It was worth it in the end, at least: Ultra Sun and Ultra Moon only took a few days to get loaded. But veekun itself is still missing some obvious Sun/Moon features, and the whole site needs an overhaul, and I just don’t know if I want to dedicate that much time to it when I have so much other stuff going on that’s much more interesting to me right now.
I finally turned my blog into more of a website, giving it a neat front page that lists a bunch of stuff I’ve done. I made a release category at last, though I’m still not quite in the habit of using it.
On a whim, I made a set of Eevee mugshots for Doom, which I think is a decent indication of my (pixel) art progress over the year?
I started idchoppers, a Doom parsing and manipulation library written in Rust, though it didn’t get very far and I’ve spent most of the time fighting with Rust because it won’t let me implement all my extremely bad ideas. It can do a couple things, at least, like flip maps very quickly and render maps to SVG.
I did toy around with music a little, but not a lot.
I wrote two short twines for Flora. They’re okay. I’m working on another; I think it’ll be better.
I didn’t do a lot of art overall, at least compared to the two previous years; most of my art effort over the year has gone into fox flux, which requires me to learn a whole lot of things. I did dip my toes into 3D modelling, most notably producing my current Twitter banner as well as this cool Star Anise animation. I wouldn’t mind doing more of that; maybe I’ll even try to make a low-poly pixel-textured 3D game sometime.
I restarted my book with a much better concept, though so far I’ve only written about half a chapter. Argh. I see that the vast majority of the work was done within the span of a single week, which is bad since that means I only worked on it for a week, but good since that means I can actually do a pretty good amount of work in only a week. I also did a lot of squabbling with tooling, which is hopefully mostly out of the way now.
My computer broke? That was an exciting week.
A lot of stuff, but the year as a whole still feels hit or miss. All the time I spent on veekun feels like a black void in the middle of the year, which seems like a good sign that I maybe don’t want to pour even more weeks into it in the near future.
Mostly, I want to do: more games, more art, more writing, more music.
I want to try out some tiny game making tools and make some tiny games with them — partly to get exposure to different things, partly to get more little ideas out into the world regularly, and partly to get more practice at letting myself have ideas. I have a couple tools in mind and I guess I’ll aim at a microgame every two months or so? I’d also like to finish the expanded fox flux by the end of the year, of course, though at the moment I can’t even gauge how long it might take.
I seriously lapsed on drawing last year, largely because fox flux pixel art took me so much time. So I want to draw more, and I want to get much faster at pixel art. It would probably help if I had a more concrete goal for drawing, so I might try to draw some short comics and write a little visual novel or something, which would also force me to aim for consistency.
I want to work on my book more, of course, but I also want to try my hand at a bit more fiction. I’ve had a blast writing dialogue for our games! I just shy away from longer-form writing for some reason — which seems ridiculous when a large part of my audience found me through my blog. I do think I’ve had some sort of breakthrough in the last month or two; I suddenly feel a good bit more confident about writing in general and figuring out what I want to say? One recent post I know I wrote in a single afternoon, which virtually never happens because I keep rewriting and rearranging stuff. Again, a visual novel would be a good excuse to practice writing fiction without getting too bogged down in details.
And, ah, music. I shy heavily away from music, since I have no idea what I’m doing, and also I seem to spend a lot of time fighting with tools. (Surprise.) I tried out SunVox for the first time just a few days ago and have been enjoying it quite a bit for making sound effects, so I might try it for music as well. And once again, visual novel background music is a pretty low-pressure thing to compose for. Hell, visual novels are small games, too, so that checks all the boxes. I guess I’ll go make a visual novel.
I’ve been a bit all over the place! And I’m starting to go nocturnal again, oh no.
art: I started drawing a header image for my itch.io page, which for a year now has been barren, save for a promise that I would soon make it unbarren.
I accidentally spent a good chunk of time toodling around with 3D modelling again, this time trying to aim for low-poly with pixel art textures. I tried a couple things, but the biggest success by far was Star Anise.
anise!!: Still not done, but asymptotically approaching done. Most of the time has been going towards the map, which has been rearchitectued several times, and which is bigger and more complicated than anything we’ve done before. Also did some regular old mechanical stuff, like doors and whatnot.
Physics! Particles! Statistical modelling! Quantum theory! How can non-scientists understand any of it? Well, students from Durham University are here to help you wrap your head around it all – and to our delight, they’re using the power of the Raspberry Pi to do it!
At the Royal Society’s Summer Science Exhibition, taking place in London from 4-9 July, the students are presenting a Pi-based experiment demonstrating the importance of statistics in their field of research.
The Royal Society Summer Science Exhibition 2017 features 22 exhibits of cutting-edge, hands-on UK science , along with special events and talks. You can meet the scientists behind the research. Find out more about the exhibition at our website: https://royalsociety.org/science-events-and-lectures/2017/summer-science-exhibition/
Ramona, Matthew, and their colleagues are particle physicists keen to bring their science to those of us whose heads start to hurt as soon as we hear the word ‘subatomic’. In their work, they create computer models of subatomic particles to make predictions about real-world particles. Their models help scientists to design better experiments and to improve sensor calibrations. If this doesn’t sound straightforward to you, never fear – this group of scientists has set out to show exactly how statistical models are useful.
The Galton board model
They’ve built a Pi-powered Galton board, also called a bean machine (much less intimidating, I think). This is an upright board, shaped like an upside-down funnel, with nails hammered into it. Drop a ball in at the top, and it will randomly bounce off the nails on its way down. How the nails are spread out determines where a ball is most likely to land at the bottom of the board.
If you’re having trouble picturing this, you can try out an online Galton board. Go ahead, I’ll wait.
You’re back? All clear? Great!
Now, if you drop 100 balls down the board and collect them at the bottom, the result might look something like this:
The distribution of the balls is determined by the locations of the nails in the board. This means that, if you don’t know where the nails are, you can look at the distribution of balls to figure out where they are most likely to be located. And you’ll be able to do all this using … statistics!!!
Similarly, how particles behave is determined by the laws of physics – think of the particles as balls, and laws of physics as nails. Physicists can observe the behaviour of particles to learn about laws of physics, and create statistical models simulating the laws of physics to predict the behaviour of particles.
I can hear you say, “Alright, thanks for the info, but how does the Raspberry Pi come into this?” Don’t worry – I’m getting to that.
Modelling the invisible – the interactive exhibit
As I said, Ramona and the other physicists have not created a regular old Galton board. Instead, this one records where the balls land using a Raspberry Pi, and other portable Pis around the exhibition space can access the records of the experimental results. These Pis in turn run Galton board simulators, and visitors can use them to recreate a virtual Galton board that produces the same results as the physical one. Then, they can check whether their model board does, in fact, look like the one the physicists built. In this way, people directly experience the relationship between statistical models and experimental results.
Hurrah for science!
The other exhibit the Durham students will be showing is a demo dark matter detector! So if you decide to visit the Summer Science Exhibition, you will also have the chance to learn about the very boundaries of human understanding of the cosmos.
The Pi in museums
At the Raspberry Pi Foundation, education is our mission, and of course we love museums. It is always a pleasure to see our computers incorporated into exhibits: the Pi-powered visual theremin teaches visitors about music; the Museum in a Box uses Pis to engage people in hands-on encounters with exhibits; and this Pi is itself a museum piece! If you want to learn more about Raspberry Pis and museums, you can listen to this interview with Pi Towers’ social media maestro Alex Bate.
It’s amazing that our tech is used to educate people in areas beyond computer science. If you’ve created a pi-powered educational project, please share it with us in the comments.
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