Eric Lengyel
@ericlengyel.bsky.social
• Creator of Radical Pie equation editor, Slug Library, C4 Engine
• Math / gamedev author
• Geometric algebra researcher
• Former Naughty Dog, Apple, Sierra
• Math / gamedev author
• Geometric algebra researcher
• Former Naughty Dog, Apple, Sierra
About two months from now, I'll be showing Radical Pie at the Joint Mathematics Meetings in Washington, D.C. I already have the best booth location on the exhibit floor.
jointmathematicsmeetings.org/jmm
jointmathematicsmeetings.org/jmm
October 29, 2025 at 10:38 PM
About two months from now, I'll be showing Radical Pie at the Joint Mathematics Meetings in Washington, D.C. I already have the best booth location on the exhibit floor.
jointmathematicsmeetings.org/jmm
jointmathematicsmeetings.org/jmm
With a couple quick color changes, Radical Pie runs in dark mode.
October 29, 2025 at 8:33 PM
With a couple quick color changes, Radical Pie runs in dark mode.
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.
radicalpie.com
radicalpie.com
October 28, 2025 at 10:39 PM
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.
radicalpie.com
radicalpie.com
Radical Pie has a gazillion typesetting parameters that you can fine-tune to your heart's content. Here's all the stuff you can tweak for parentheses, brackets, braces, etc.
October 24, 2025 at 3:53 AM
Radical Pie has a gazillion typesetting parameters that you can fine-tune to your heart's content. Here's all the stuff you can tweak for parentheses, brackets, braces, etc.
When I wrote PGA Illuminated, I had to paste an equation in Illustrator to draw highlights and annotations like these. Not any more. With Radical Pie, they get drawn directly in the equation editor, they auto-resize during edits, and everything stays live when embedding in Word.
October 21, 2025 at 11:23 PM
When I wrote PGA Illuminated, I had to paste an equation in Illustrator to draw highlights and annotations like these. Not any more. With Radical Pie, they get drawn directly in the equation editor, they auto-resize during edits, and everything stays live when embedding in Word.
The Radical Pie editor has 16 palettes across the top containing just over 600 common symbols and mathematical structures. (The entirety of Unicode can be accessed through a separate dialog.) radicalpie.com
October 20, 2025 at 9:35 PM
The Radical Pie editor has 16 palettes across the top containing just over 600 common symbols and mathematical structures. (The entirety of Unicode can be accessed through a separate dialog.) radicalpie.com
Some people are particular about how much their integrals lean forward. Radical Pie is going to let you choose whatever angle you want, and it will generate the corresponding Bézier curves. These examples range from −2.5° to 15° right of vertical through the center.
October 7, 2025 at 11:05 PM
Some people are particular about how much their integrals lean forward. Radical Pie is going to let you choose whatever angle you want, and it will generate the corresponding Bézier curves. These examples range from −2.5° to 15° right of vertical through the center.
Here's a quick video showing an equation being entered into Radical Pie, an annotation being attached to that equation, and more annotations being attached to the first annotation.
October 3, 2025 at 6:02 AM
Here's a quick video showing an equation being entered into Radical Pie, an annotation being attached to that equation, and more annotations being attached to the first annotation.
Radical Pie has entered beta testing! I expect the final release to be available by the end of October.
October 3, 2025 at 2:58 AM
Radical Pie has entered beta testing! I expect the final release to be available by the end of October.
All of the rendering in Radical Pie is done by Slug, so I capped the zoom magnification at one million percent.
August 11, 2025 at 5:15 AM
All of the rendering in Radical Pie is done by Slug, so I capped the zoom magnification at one million percent.
Combined, FGED 1 and 2 contain 5503 individual equation objects that I originally made in MathType years ago. Some of them had to go through Illustrator because they contained additional graphics and annotations (Figure 1.5 and Equation (1.78), for example).
August 8, 2025 at 9:30 PM
Combined, FGED 1 and 2 contain 5503 individual equation objects that I originally made in MathType years ago. Some of them had to go through Illustrator because they contained additional graphics and annotations (Figure 1.5 and Equation (1.78), for example).
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.
August 8, 2025 at 12:32 AM
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.
Update: Now it's 534 glyphs.
June 13, 2025 at 8:22 PM
Update: Now it's 534 glyphs.
I've been making a special font for Radical Pie. It started out as a way to provide a handful of symbols that aren't in Unicode. As I grew annoyed by errors, inconsistent weights, and missing glyphs in existing fonts, I kept creating more glyphs for my own. It's up to 463 now!
June 12, 2025 at 1:37 AM
I've been making a special font for Radical Pie. It started out as a way to provide a handful of symbols that aren't in Unicode. As I grew annoyed by errors, inconsistent weights, and missing glyphs in existing fonts, I kept creating more glyphs for my own. It's up to 463 now!
Radical Pie has 16 palettes containing mathematical symbols and various typographic structures. Let me know if you think there should be anything else available here for quick access.
June 11, 2025 at 7:36 AM
Radical Pie has 16 palettes containing mathematical symbols and various typographic structures. Let me know if you think there should be anything else available here for quick access.
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!
June 5, 2025 at 7:47 PM
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!
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.
terathon.com/blog/transwe...
terathon.com/blog/transwe...
May 23, 2025 at 7:27 AM
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.
terathon.com/blog/transwe...
terathon.com/blog/transwe...
Yeah, this is also how floor and ceiling are typically implemented. Here's my floor() code, for example:
May 21, 2025 at 11:10 PM
Yeah, this is also how floor and ceiling are typically implemented. Here's my floor() code, for example:
Slug version 7.4 has been released. This update includes several small feature improvements.
sluglibrary.com
sluglibrary.com
May 15, 2025 at 5:07 AM
Slug version 7.4 has been released. This update includes several small feature improvements.
sluglibrary.com
sluglibrary.com
An electronic edition of PGA Illuminated is now available here:
www.amazon.com/dp/B0F7FZLNV...
www.amazon.com/dp/B0F7FZLNV...
May 4, 2025 at 12:38 AM
An electronic edition of PGA Illuminated is now available here:
www.amazon.com/dp/B0F7FZLNV...
www.amazon.com/dp/B0F7FZLNV...
I finished implementing stretchable arrows in Radical Pie today. I may have gone a little nuts with the features, but they turned out really well.
April 25, 2025 at 1:32 AM
I finished implementing stretchable arrows in Radical Pie today. I may have gone a little nuts with the features, but they turned out really well.
What I ended up doing was transforming axis-aligned rectangles into a pair of overlapping pentagons arranged like this. It renders without artifacts and fools both Acrobat and Chrome so we get a consistent appearance. Equations in PDFs look nicer as a result.
April 22, 2025 at 1:19 AM
What I ended up doing was transforming axis-aligned rectangles into a pair of overlapping pentagons arranged like this. It renders without artifacts and fools both Acrobat and Chrome so we get a consistent appearance. Equations in PDFs look nicer as a result.
Adobe Acrobat and the Google Chrome PDF viewer both have an annoying "feature" that detects axis-aligned rectangles in a vector image and renders them with control points snapped to the pixel grid.
April 20, 2025 at 6:34 AM
Adobe Acrobat and the Google Chrome PDF viewer both have an annoying "feature" that detects axis-aligned rectangles in a vector image and renders them with control points snapped to the pixel grid.
I got a shiny new button for Radical Pie in the Word UI.
April 17, 2025 at 2:54 AM
I got a shiny new button for Radical Pie in the Word UI.
Good implementations of wide tilde marks have always been hard to find. And good luck if you want a wide tilde *under* an expression (which I sometimes do). Here's a comparison of wide tildes produced by various equation editors that highlights the differences in quality.
April 15, 2025 at 2:16 AM
Good implementations of wide tilde marks have always been hard to find. And good luck if you want a wide tilde *under* an expression (which I sometimes do). Here's a comparison of wide tildes produced by various equation editors that highlights the differences in quality.