dactyl-font
NOTE: Best viewed at https://terryspitz.github.io/dactyl-font/
Dactyl: What & Why
Dactyl is a functional font generator written in F#, in service of ticking ‘create a font’ off my bucket list, in style! Dactyl is parameterised with a large (and growing) number of inputs including axes common in variable fonts such as stroke thickness and x-height and more unusual ones like roundness and end-bulbs. Dactyl is an exercise in understanding how fonts can be built in code using both ‘words and rules’ - a minimal set of general shape logic along with a minimal set of shape data per glyph. This work will hopefully help me improve my AI font generator DeeperFont though at the moment the technologies are quite different and combining them will be an interesting future challenge.
You can explore Dactyl live in your browser using the Dactyl Live explorer. Note the Reset and Random icons next to the title. The settings deliberately extend beyond ‘normal’ to show how the fonts behave (and often misbehave) under extremes. There is also Spline explorer for exploring glyph string definitions.
Here is some of Dactyl’s checkered development history:
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A few predefined Dactyl fonts are available to download in the ttf subdirectory. Note: these fonts are still a work in progress and do not have good spacing or kerning, or even good shapes under some settings. In future I plan to make fonts downloadable afte customising in the live browser. Some sample fonts are here.
Spiro curves
Dactyl fonts use and are inspired by Ralph Levien’s Spiro curves. I used Wiesław Šoltés’s C# port which I’ve ported to F# to run under the fantastic Fable to transpile to javascript, meaning I can write the whole thing in beautiful F#.
Raph superceded his spiro curves in 2018 with https://github.com/raphlinus/spline-research, which are available with the ‘spline_not_spiro’ checkbox. These offer direct control of tangents specifically to help font design (this feature was also later added to Spiro curves as Anchor/Handles). See https://www.youtube.com/watch?v=eqNngVkMBzE
Variable fonts
Dactyl is also inspired by Variable Fonts technology. Unfortunately though it isn’t easy to output a Dactyl font as a variable font since they can only interpolate between two glyphs with the exact same knot points, which is hard to achieve with Dactyl’s spiro bezier curves.
https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Fonts/Variable_Fonts_Guide
“The five registered axes are weight, width, slant, italic, and optical size.”
https://developers.google.com/web/fundamentals/design-and-ux/typography/variable-fonts
https://alistapart.com/article/user-interfaces-for-variable-fonts/
Font creation/import formats
FontForge is an open-source font editor which supports Spiro.
Since none of the font interop formats I found support spiros directly the Dactyl generator writes files in FontForge native format (a .fsdir directory of .glyph files), which can be loaded into FontForge and used generate TTF fonts.
FontForge is also useful to view and interact with the letter glyphs in detail: it has great validation, viewing and editing features.
http://designwithfontforge.com/en-US/Importing_Glyphs_from_Other_Programs.html
http://unifiedfontobject.org/versions/ufo3/glyphs/glif
https://opentype.js.org/glyph-inspector.html
Font design
This project is a great opportunity to dive into the vast world of typographic design. A few of the sites and articles that have caught my eye so far are below.
http://designwithfontforge.com/en-US/Creating_o_and_n.html
http://designwithfontforge.com/en-US/Trusting_Your_Eyes.html
https://www.reddit.com/r/neography/comments/8186cc/creating_fonts_with_inkscape_and_fontforge_part1
https://www.typography.com/blog/text-for-proofing-fonts
On letter spacing, tracking and kerning:
http://www.fermello.org/FernandoMello_essay.pdf
https://www.fontshop.com/content/adventures-in-space_spacing
https://typefacts.com/artikel/kerningtest
https://www.typography.com/blog/typographic-illusions
https://www.typography.com/blog/turning-type-sideways
https://design.google/library/google-fonts