LGM 2019 – A new spline
Channel: Libre Graphics Meeting
Date: 2019-07-17

Raph Levien, Jacob Rus
A new spline

What is the best way to interactively draw 2D vector graphics? The Bézier pen tool has been the standard for the past half century, a testament to its mathematical and computational simplicity and its flexibility as a design tool, but it has a steep learning curve and often leaves even experts drawing lumpy shapes or spending excessive time smoothing them. Interpolating splines are a promising alternative with a more direct user interface, but haven’t caught on yet. The Euler spiral spline (the basis of Spiro) gives smooth results but doesn’t converge reliably; the Hobby spline (Metafont) is the reverse.
In this talk, we present a new spline which is the best of both worlds, giving G2-continuous curves by construction, very robust, and with good locality. The spline also has explicit control over tangents, which is important for font design and is designed to have a better user experience than the “one-way” constraints in Spiro. The goal of this presentation is to present the work and open a dialog both with users about what they want from curve design tools, and with open source developers about how to ship a better curve design experience.

Raph Levien is a long-time open source developer of graphical software, with contributions including Gimp, Ghostscript, font tools, and major improvements in the Android text stack. His PhD from UC Berkeley is on Spiro, an interpolating spline tuned for font design. His Inconsolata font was designed using those tools. Based in Berkeley, CA, after 11 years at Google, he is now independently working on a variety of projects, including Rust graphics and sound infrastructure.

Jacob Rus is a professional dabbler, with broad interests in information design, cartography, color vision, photography, computer input ergonomics, and more abstractly in understanding and improving human–computer interfaces. His recent research projects include new tools for photo color grading, vector graphics curves, world map projections, alternative computer keyboard designs, interactive online explanations of mathematical topics, and chasing a 2-year-old around town.

https://spline.technology 

This presentation was recorded on Friday, 31st May 2019 as part of Libre Graphics Meeting 2019, at the Hochschule der Bildenden Künste Saar in Saarbruecken, Germany. To learn more, see https://libregraphicsmeeting.org/2019/.