Hacker News Reader

Yeah, there is an entire science on how to do font rendering properly. Perceptually you should even take into account if you have white text on black background or the other way as this changes the perceived thickness of the text. Slightly hinted SDFs kind of solve that issue and look really good but of course making that work on CPUs is difficult.

View on HN

What's difficult with font SDFs on the CPU? The bezier paths?

I made myself a CPU SDF library last weekend, primarily for fast shadow textures. It was fun, and I was surprised how well most basic SDFs run with SIMD. Except yeah Beziers didn't fair well. Fonts seem much harder.

SIMD was easy, just asked Claude to convert my scalar Nim code to Neon SIMD version and then to an sse2 version. Most SDFs and gaussian shadowing got 4x speedup on my macbook m3. It's a bit surprising the author has so much trouble in Rust. Perhaps fp16 issues?

I haven't looked at this recently but from what I remember rendering from SDF textures instead from simple alpha textures was 3-4 times slower, including optimizations where fully outside and inside areas bypass the per pixel square root. Of course SIMD is a must, or at least the use _mm_rsqrt_ss.

Reply on news.ycombinator.com