Eric Lengyel

New blog post: A Decade of Slug
This talks about the evolution of the Slug font rendering algorithm, and it includes an exciting announcement: The patent has been dedicated to the public domain.
https://terathon.com/blog/decade-slug.html

Currently working on fur rendering for Chapter 15 in FGED3. Thor, the dog of thunder, is helping with some real-world BRDF references.

FGED3 adds five new chapters to the series:

11 • Curves
12 • Motion Operators
13 • Models and Animation
14 • Advanced Shading
15 • Special Effects

I'm shooting for a SIGGRAPH 2026 release.

(The cover is not necessarily final.)

I am excited to announce the release of Radical Pie, version 1.0! This is the professional equation typesetting application that I've been working on for the last year. See the website for details.
https://radicalpie.com/

All the beautiful font rendering and exquisite typography in DOOM The Dark Ages came from the Slug Library. I'm excited that it's part of game!

Slug renders fonts directly from the original Bézier curves on the GPU and provides support for kerning, ligatures, accents, a wide variety of languages, and accessible text scaling throughout the entire UI.
https://sluglibrary.com

Radical Pie has entered beta testing! I expect the final release to be available by the end of October.

Radical Pie is a professional WYSIWYG equation editor for Windows 10/11. It's meant to be used for everything from slide presentations and YouTube videos to full-length textbooks.
https://radicalpie.com

I've written a new blog post called "Dual Approaches to Projective Geometric Algebra".
https://terathon.com/blog/dual-pga.html

Radical Pie 1.8 was released today, and it includes the ability to parse LaTeX. If you have a big equation already written in LaTeX, then you can just copy/paste the plain text into the editor, and Radical Pie will lay it out visually.
radicalpie.com

All of the rendering in Radical Pie is done by Slug, so I capped the zoom magnification at one million percent.

The drawing and annotation tools in Radical Pie are finished! Now, I can type an equation and add highlighting, arrows, labels, etc., as shown in the following examples. All drawing objects are attached to anchor points in the equation, so they move and resize dynamically.

This means all of the major features are now complete, so we're getting close to release!
radicalpie.com

The equation editor called Radical Pie that I developed throughout 2025 has been getting a lot of nice feature updates over the four months since its initial release. We're already up to version 1.7. Free trial available on radicalpie.com.

I'm surprised to see 4K monitors still under 5% in the Valve Hardware Survey.
https://store.steampowered.com/hwsurvey/Steam-Hardware-Software-Survey-Welcome-to-Steam

I wrote a new blog post about something I'm calling the transwedge product. It allows us to fully decompose the geometric product into discrete parts using the primitive operations of the exterior algebra.
https://terathon.com/blog/transwedge-product.html

Radical Pie has a large number of user-configurable parameters that control precise spacing, positioning, sizing, and various shapes (like arrowheads) in an equation. The final count is 335, and they can all be set in 23 different panels shown in a couple big dialog boxes.