GENUARY Day 22 – Pen plotter Ready

by Piter Pasma

What’s a plotter?

It’s a drawing robot holding a pen. Kind of like a 3D printer, except for 2D and it’s not really a printer.

What if I don’t have a plotter?

You can still make a plotter ready artwork! Maybe send it to someone who does have a plotter. Or simply take this as a challenge to produce a completely line based artwork, that may or may not one day be executed by a proper drawing robot.

What do I need to consider?

A work is considered “plotter ready” if it can be drawn using a plotter.

The big limitation is that a plotter can only draw lines. And that it cannot erase lines. It can also not draw over the same spot 20 times because the robot doesn’t care and the pen will rip through the paper.

In theory you can draw a dot with a very short line or small circle, however it takes a small but non-trivial amount of time to lift up the pen and lower it again, so if you have 50 000 dots, this will take a lot of time. So it pays off to draw a small number of long lines. Or even just one very long line.

Changing pens is a hassle, so you don’t want to do that too often, or preferably not at all. It’s also hard to make sure each new pen is neatly aligned with the earlier ones.

Now you might wonder why people even bother.

I’m wondering why people even bother

The upside of plotters is that they are ridiculously precise and can draw with a super fine lines (although it’s hard to find reliable pens finer than 0.25mm). And you can get more interesting textures than printers using e.g. ballpoint or fountain pens.

You can even use paint brushes or charcoal or whatever else you can think about, though each of these methods comes with their own unique challenges.

It’s quite hypnotic to look at and the robot continues plotting at night when you’re not looking.

OK fine how do I do this?

Generally plotter artists use SVG files to represent their plots.

In case you don’t know how to SVG, you only need to learn a super tiny bit about SVG, because you only need/get to draw lines. This means you don’t get/need to use the fancy SVG filters, or most complicated stuff. In fact you don’t get to use the fill attribute! Because you only get lines, which includes having to use only lines to hatch filled areas.

To help you out we have made various pieces of code available that you can download and change and adopt into your own thing:

• template D (src) is probably the simplest to use template. This one splits the generating of lines and generating of the corresponding SVG into two functions. It draws a version of Georg Nees’s Schotter.
• template A (src) is also probably the simplest to use template, if you happen to prefer it. It doesn’t really split stuff into functions, but builds the SVG step by step. It draws a simple spiral.

And then because I decided to get fancy and/or distracted, I made these templates for you to enjoy:

• template B (src). This one also draws a spiral, but it distorts it using some wobbly noise. Then it draws the same spiral again but backwards, and distorting in the opposite direction. This creates a cool moiré pattern.
• template D2 (src) is iterating on Georg Nees’s Schotter, a variation.
• template C (src) might take a while to render. It kinda does the same as template B, except the distortion is based on the lighting of a 3D raymarched scene instead of a noise function, showing the GENUARY logo. It also contains a nice “clip” function, allowing you to clip a bunch of lines against a 2D SDF. It also increases the viewbox resolution to 1e5, and rounds all the coordinates to integers to save more space. It also uses a variation on the path function that uses relative coordinates, and saves even more space in the SVG. And it’s also got a line simplification function. It’s also pink.