This is wonderful news, and my sincere thanks to the author.
I remember coming upon this algorithm several years ago, and thinking it was extremely elegant and very appealing, but being disappointed by the patent status making it unusable for FOSS work. I really appreciate the author's choice to dedicate it to the public domain after a reasonable amount of time, and congratulations on the success it had while proprietary!<p>Now if I ever get around to writing that terminal emulator for fun, I'll be tempted to do it with this algorithm for the code's aesthetic appeal.
> I was granted a patent for the Slug algorithm in 2019, and I legally have exclusive rights to it until the year 2038. But I think that’s too long. The patent has already served its purpose well, and I believe that holding on to it any longer benefits nobody. Therefore, effective today, I am permanently and irrevocably dedicating the Slug patent to the public domain.
Yes, now that SDF font rendering is the industry's preference, he drops the software patent. That is, he is dropping the patent because it isn't a commercially viable piece of software, not because he is ethically opposed to it. Great virtue signaling though.
Seems more like he had the patent long enough to build a sustainable business from his own work, and now he’s been able to earn enough from it that others’ implementations aren’t a risk to him.<p>Which is kind of the entire point of patents, just that they last way too long relative to the speed of technological progress
He said "holding on to it any longer benefits nobody", implicitly including himself. He may believe that it's to his advantage for the patent to be more widely used.<p>Which makes sense--I don't doubt that he is a subject matter expert where this patent is concerned. If this algorithm continues to be widely used or its use increases, then that would be likely be good for him.
SDF font rendering was common long before Slug, and Slug is supposed to be the better solution (I haven't used it though, so cannot comment on its pros and cons vs SDF, but one obvious disadvantage of SDF is that you still need a font atlas texture, and that can get very big if you need to render some East Asian character sets).
SDF font rendering has been around 20+ years though? Valve really popularized in their 2007 SIGGRAPH paper and Chlumský developed MSDF font rendering in a 2015 thesis.
SDF font rendering was an industry standard maybe from 2007-2010. and you probably won’t believe what happened to OpenGL since then. Don’t even look into at what people are doing with GPUs these days, you won’t like it one bit!
You do realize he could've just kept it until 2038, right? This was completely unforced.
SDF rendering is just a fuzzy blobby approximation.
Software patents valid for 8 years is actually something I could get behind.
There are two ways to get winding numbers and then decide on filled or empty by some rule like non-zero or even-odd:<p>a) The winding number of a point is the number of intersections of a scanline and a closed path.<p>b) The winding number around a point is the total angle subtended by the path at that point.<p>Slug uses approach a) and that comes with a lot of edge cases (see chart in the post) and numerical precision issues. The approach by loop & blinn uses b) and is thus simpler and more robust. Likewise the patent on that one expired too: <a href="https://news.ycombinator.com/item?id=47416736#47420450">https://news.ycombinator.com/item?id=47416736#47420450</a>
Loop and blinn does not compute a winding number using the b) method. It avoids the issue of a winding number by assuming there's only 1 bezier curve per triangle, which requires a complicated triangulation step. It can produce some nasty geometry in more complex cases. With Slug, you can use only 1 quad per glyph if you want.<p>Also just to clarify regarding this statement:<p>> Slug uses approach a) and that comes with a lot of edge cases (see chart in the post) and numerical precision issues<p>Slug does not have numerical precision issues. It's the breakdown into different cases that _solves_ those issues, whereas your statement makes it sound like slug has _both_ the case complexity and the precision issues.
His latest project is <a href="https://radicalpie.com/" rel="nofollow">https://radicalpie.com/</a><p>A Professional Equation Editor for Windows 10/11 for 60$ that uses Slug for rendering. Presumably he‘s using it to write his great FGED books.
I used Slug at a previous job. It is an excellent, artfully crafted library; really the pinnacle of software engineering in my opinion. Thanks to the author for donating the algorithm to the public domain!
Amazing, Thank you Eric!!<p>Also, Microsoft's Loop-Blinn patent for cubic curves will expire on March 25. These might change the landscape of text rendering...
Thanks Eric, much appreciated. How would you compare your approach to something like Vello (<a href="https://github.com/linebender/vello" rel="nofollow">https://github.com/linebender/vello</a>)?
Love it when someone who makes complex, helpful software is rewarded for their efforts. More stories like this!
Thanks, Eric; for this, and for my start as a software engineer — my first commercial development work was consulting as an 18 year old building games with C4. I'm really glad Slug was able to find commercial success for you in the way that C4 unfortunately wasn't able to.<p>For those of you who aren't familiar with Eric's work, he's basically the Fabrice Bellard of computer graphics.
I am sorta in a position where implementing a glyph renderer as a compute shader would be helpful. This is a great opportunity to use this as a reference... exciting weekend project!
Damn, I worked with the author's game engine (C4) about... 20 years ago now while still in school, didn't know they were still active in that area!
I am not at all familiar with game development. This article reminds me of Casey Muratori mentioning a font issue in game development environment from a random podcast. On web, you can just fetch a google font whatever. No problem. On a local machine, you tend to look a well-established software like harfbuzz. But then harfbuzz could be rather a big dependency. A game is self-contained and you want your font looks cool and unique to your game, like the Diablo font. So it becomes a design issue. It's an awesome approach to let GPU render fonts. I cannot imagine how many game devs had font issues where they realized that they might have to learn how to render fonts as well not just characters and grass.
> well-established software like harfbuzz<p>Harfbuzz is only one piece of the puzzle, it's not a text renderer, only a 'text shaper' (e.g. translating a sequence of UNICODE codepoints into a sequence of glyphs). The actual font handling and text rendering still needs to be done by some other code (e.g. the readme in Mikko Mononen's Skribidi project gives a good overview about what's needed besides the actual rendering engine: <a href="https://github.com/memononen/Skribidi/" rel="nofollow">https://github.com/memononen/Skribidi/</a>)
Is it on ShaderToy yet? :D
So nice to see this here.
The author's books are awesome resources for graphics and C++. It's a shame there seem to be fewer print editions available these days!?
This is super cool. A few years ago I was wondering if Ruffle could do something similar, incorporate some kind of GPU accelerated vector graphics.<p>At the time they were going with, approximating the curves out of triangles. I don't know if they're still doing that though.
> I was granted a patent for the Slug algorithm in 2019, and I legally have exclusive rights to it until the year 2038. But I think that’s too long.<p>This is cool but I did not know software patents were still a thing in the US.
> But I think that’s too long. The patent has already served its purpose well, and I believe that holding on to it any longer benefits nobody.<p>Damn dude didn't you pay like ... over $10k for that patent?
So now the algorithm is patent-free, and the vertex and fragment shaders are open-sourced with the MIT license, what we presumably need is some open-source code to take Bezier curves from a font file (or from the loaded data from FreeType or whatever), and process them into the data format that Slug expects.<p>Also thank you to Eric Lengyel, I have had my eye on Slug for a while and wished it was open-source.
Lengyel continues to be standup dude, kudos!
I've been following this project for a while. Nice to see the progress.
Finally, some <i>good</i> video game development news!
Awesome algorithm and thank you for donating it to open source!
Thank you!
Amazing! Thank you, Eric!
Oh wow this is crazy. This was a project that was reasonably successful commercially. And now it’s just being given away open source? What an absolutely incredibly gift to the community!!
Not quite, just the pixel/vertex shaders and the algorithm is public domain. Slug "the software package" is not open source (you can get a copy of it along with C4 Engine for $100 to take a peek if you want, though).
Thank you for your service!
Here's an alternate if you're also getting connection reset errors:<p><a href="https://web.archive.org/web/20260317185928/https://terathon.com/blog/decade-slug.html" rel="nofollow">https://web.archive.org/web/20260317185928/https://terathon....</a>
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Please don’t post AI generated comments, it’s against the rules and also just a waste of people’s time.
Glyph complexity has no effect on the calculations done in the pixel shader and does not change how glyphs are preprocessed. There are no edge cases. If you'd like to see some ridiculously complex fonts get rendered with Slug, check out the 8th page in the demo at sluglibrary.com. Some of those individual glyphs are composed of over 1000 Bézier curves!