That magic number

[Fishrock123]

Where's the magic number 0.70710678118654757 from?

[rreusser]

1 / sqrt(2) ~ 0.70710678118

[mattdesl]

Yup, or `sqrt(0.5)`. Lately I’ve been wondering if the following is a cleaner alternative to my current afwidth calculation: ``` float afwidth = fwidth(dist) * 0.5; ```

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On Oct 16, 2017, at 7:10 PM, Ricky Reusser ***@***.***> wrote: 1 / sqrt(2) ~ 0.70710678118 — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub, or mute the thread.

[rreusser]

I was wondering the same when I played with this. (If I understand correctly, that is,) is there a big difference in practice between sqrt(0.5) * (|dfdx| + |dfdy|) and sqrt(dfdx^2 + dfdy^2)? I guess the former just introduces a bit of directional bias in the amount of antialiasing. Of course they're rectangular pixels though, so that's not necessarily a bad thing. And the absolute value is probably faster than a sqrt.

[Fishrock123]

float afwidth = fwidth(dist) * 0.5;

This does appear to look a bit cleaner to me, fwiw. Edit: maybe not?