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The Art of Polar Plotters: John Proudlock on Generative Portraiture & Vertical Plotters

Posted by Michelle Chandra on

While I use an Axidraw pen plotter to draw my generative art designs, there are many sophisticated folks building their own drawing machines such as polar plotters! John Proudlock is one such person, and was kind enough to transform a recent photo of me into a generative portrait (see below!) In this short interview, John shares info on building his own drawing machines, and why he makes generative art.

Like many of the generative artists I follow on Instagram, I actually don't know much about your background! What led you to generative art and building your own polar plotter?

I found generative art by accident.

I was given a Raspberry Pi (a small computer) and was wondering what to do with it. Around the same time I saw a youtube video about a ‘polar plotter’ and thought… I wonder if I could make one. I knew a little bit of electronics/software, mostly forgotten, so it felt like a fun way of re-learning all the things I’d forgotten.

john proudlock moon pen plot polar plotter generative artwork creative code

It turned out that building a machine that can make lines on paper wasn’t too difficult but that just led onto the really hard question: What should it draw?

Patterns to the rescue! It turns out simple, repeating patterns look fantastic (to me) drawn out on paper by my wobbly plotter machine. And that is ‘generative art’ and it has fascinated me ever since.

For those who might not know, can you describe what a polar plotter is, and how it differs from a precision plotter like an Axidraw? How easy (or difficult!) was it for you to build a polar plotter?

A polar plotter is really simple mechanically. They’re usually mounted vertically, so imagine you have a wall and you hang the following: Two motors with drive shafts pointing into the room (top corners), a cord (in red), a pen (P) and a couple of counterweights (CW).

polar plotter mechanism diagram by john proudlock
As the motors turn, the pen is dragged across the surface of the paper and you draw something!

It turns out they’re easy to make, but you need to find/write some software to control the motors so you can draw lines from and to the right place. I added a pen lift mechanism so you can draw individual lines.

You recently transformed a photo of me into a nifty generative line portrait I drew with my Axidraw. Can you explain the algorithm behind the portrait? What led you to write this algorithm?

This algorithm renders photographs using an old pen and ink technique called ‘hatching’. 

michelle chandra generative pen plot portrait by john proudlock

I wanted to write an algorithm to create ‘hatching’ style pictures, but I wanted to keep some variation and randomness in the final picture.

In the end I interpreted images as maps, where dark areas were ‘food’. I then tracked how a goat, with a jetpack, might move around the landscape. It sounds weird but I explain it a little better in this TEDx talk.

For your picture, Michelle, there are 4 types of goat. One only walks North/South. One goes East/West. The other two only travel in diagonals.

What interests you about drawing photos as generative art?

I think there’s something magical about taking the analogue nature of photographs and interpreting them with algorithms spinning in a silicon processor on a circuit board. Transferring the output of the algorithm back into the real world, using a pen to mark paper is convoluted and difficult and the unique nature of the process makes it precious, to me.

What are some of your favorite generative drawings from the last year and why do you like them?

I love collaborations and worked with an image of NYC by a Russian photographer, Tatiana Fet. I mimicked a photographic technique called dual exposure to interlay this image with The Statue of Liberty. You can see a timelapse of this piece being drawn on my insta account.

john proudlock generative photo pen plot polar plotter tatiana fet

I’ve also worked on writing software that creates virtual drawing machines based loosely on the type of physical machine built by James Gandy. There are so many parameters in these algorithms that I find them overwhelming and difficult to get an interesting image (usually I get a mad squiggle) but when it works, the results can be stunning and are unique to my machine.

john proudlock harmonograph polar plotter geometry art pen plot

I find colour images really challenging on the vertical plotter, because the pen change routine is a bit of a shambles and I often knock the register off (meaning the different colour sections don’t align). That makes it all the more rewarding when I get it right and that led to a series of colour images that I’m really proud of.

john proudlock generative polar plot star wars rdd2 multiple colors


Looking back, are there things you would change about your first polar plotter?

All of it! I built this machine stage by stage, and then went back and rebuilt every part that I thought could work better. I’ve rebuilt every bit of the machine, some bits several times.

What's next for you in drawing machine land? Do you have any advice for folks interested in building their own vertical plotters?

I’d quite like to tidy the code up and make it open source so that people can build their own machines along a blueprint of what I’ve done. I’d also like to get back to drawing with stabilo 88 colours; my recent work has all been with cartridge v5 pilot pens, which are indestructible, but have a limited colour set.

There are quite a few home-builds around so do some research and lean on their designs to guide you. If it’s not working out, you’ll have learnt something useful and there are always kits to buy and help you skip any bits of the development that are difficult. I found was a really useful reference site, there are a load of links out to other builders around the world)

Where can people find you online to learn more info?

You can find some articles I’ve written, my gallery, and a TEDx talk here:

All Generative Art, All the Time

But what if you want to learn more?! Check out these additional blog posts:

michelle chandra of dirt alley design

Dirt Alley Design was founded just off a dirt alley in San Francisco in December of 2016 by artist Michelle Chandra. Inspired by the beauty of street grids, Michelle invented maze maps in which she transforms street grids into mazes. In 2019, she began a new project - geometry art created with code and drawn with a pen plotter. Follow her on Instagram and Twitter @dirtalleydesign where she posts new spirograph designs daily 

artist process generative art pen plotter plotter printmaking

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