Creating Minimalist, Low-Poly Illustrations with Delaunay Triangulation

There was a trend not too long ago in the design world with minimalist illustrations consisting of triangles. A lot of different designers and digital artists gave this style their own shot. Some took a manual approach, carefully plotting and drawing the individual triangles by hand, some clever (or perhaps lazy) designers took a shortcut. They used Delaunay triangulation (named after mathematician Boris Delaunay) to generate or aid in the creation of these types of Illustrations.

How does it work?

At its basic level, here’s how the software works:

1. A mesh of points is generated (by hand or automatically) and triangles are drawn from these points. Which points are connected to form which triangles is determined by maximizing the smallest angle of all the angles of the triangles. Delaunay triangulation avoids making any triangles with small angles whenever possible, and instead seeks to equalize all angles whenever possible.
2. The color of each triangle is determined by automatically averaging pixel color of all pixels contained within that triangle in the original image.

The end result is this ‘minimalist, polygonal’ style that can carefully be adjusted to concentrate detail in important area of an image (such as eyes, other small features of a subject), and leave unimportant areas of the image as large, flat-colored triangles. It conveys a minimal, geometric look that mimics the triangular polygons that often comprise 3D models made in software such as Blender. This is why the label of ‘low-poly’ is often applied to this style of Illustration.

How to make these Illustrations:

There are various programs out there (both free and paid) that can aid in creating these Illustrations, or even generate them automatically. Implementations have been made that can even apply this style to videos. Some are better than others, and I’ll go over some of the better known implementations below.

Image Triangulator, by Concept Farm

This is my favorite implementation that I’ve tried due to it’s easy of use, useful keyboard shortcuts, and ability to dynamically generate triangulation points based on adjustable sliders. The triangulated mesh is even visible and calculated in real-time, making you aware of the result with each movement of the mouse, before any points are set. Other comparable software usually makes these features paid (or lacks them entirely), but Image Triangulator is completely free, and works on both Windows and MacOS.

Image Triangulator can export final images to vector or bitmap formats. This means that you can save it to a PDF and bring it into other software like Adobe Illustrator for further editing. One additional great feature is the ability to save the triangulation point locations to a text file. With that file, if you decide to go back and edit the image, you can re-import point locations and continue from where you left off, or even transfer point locations to another image.

In my opinion, this is the only implementation worth using. The one downside is that the triangulation point eraser can only erase a single point at a time. An ideal version of the eraser would have an adjustable eraser radius, maybe even with a softness feature so that points on the periphery of the eraser radius only have a chance of being erased.

DMesh by Dofl Y.H. Yun

DMesh has a fancier, more modern looking interface, but lacks several features that I consider to be essential when making these illustrations. The base program is free to download and use, but dynamically generating triangle points is a paid feature. Additionally, there’s no way to zoom in and out of the image, making it difficult to precisely place points manually in crucial areas, and even making it impossible to work with images that are larger than your monitor resolution. Finally, there’s no way to go back and edit the points on an image when you close the program. Otherwise the feature set is basically the same as Image Triangulator, with some minor differences in how the mesh is displayed.

The only superior feature that DMesh has over Image Triangulator is a better point eraser, in that it can erase more than one point at a time. One other small advantage that DMesh has is that it can superimpose the triangulated mesh over the original image at an adjustable opacity.

Delaunay Image Triangulation Brush for Illustrator with Scriptographer by Creatogether

For those who prefer to stick within one software, Creatogether has coded up an implementation of Delaunay Triangulation for Adobe Illustrator. It’s an interactive tool that works as a brush over an embedded image within Illustrator.

The caveat is that this tool requires Scriptographer, a deprecated software which only works with Illustrator CS5. No newer versions of Illustrator are compatible. But if you have a copy of Illustrator CS5, Scriptographer still works, and is free to download. Its original creators (Jürg Lehni, and Jonathan Puckey) have moved on to Paper.js, a totally web-based version of their software.

Some additional downsides of this tool include the inherent slowness of Illustrator, the lack of an ability to erase points, and the fact that triangulation points cannot be dynamically generated at all. With the previous two tools having the ability to export to PDF, there’s really no reason to use this script anymore.