Donut math: how donut.c works | Hacker News Reader

Donut math: how donut.c works

a1k0n.net

196 pointsmr_o4714 comments

Reminds me of this classic IOCCC entry implementing a flight simulator, where portions of the source code are formatted to resemble a plane:

https://www.ioccc.org/1998/banks.orig.c

https://www.ioccc.org/years.html#1998_banks

Interesting.

Tangentially reminds me of my own animated GIF app that I made a while ago.

https://www.gifcii.fun

This is seriously cool

That’s the kind of thing that had me learn coding many years ago ( watching demoscene productions).

What platform does this compile on? Didn't work for me on a recent model M1 MacBook Pro.

What were the errors?

I got it to compile in Linux on x86-64, with the following tiny changes:

- Add #include <stdio.h> (for printf())

- Add #include <string.h> (for memset())

- Add "int" before the initial bare declaration of "k"

I compiled it with:

    $ gcc -o donut -std=c89 donut.c -lm

Which includes:

- Specifying an old language standard to get rid of the need to say "int" before main()

- Linking the math library ("-lm") for the trig functions.

Update: minor grammar and clarification.

With -std=c89 you shouldn't need that `int k`, right?

Further, you can add includes on the command line

    cc -std=c89 donut.c -include stdio.h -include string.h -include math.h -lm

Then the source can be left as is.

It should compile without the #includes, possibly didplaying some compiler warnings.

Yeap. A

   gcc -lm donut.c

is enough. Also type and return type default to `int` so this doesn't need change either.

(2011)

reminds me of stuff i based in basic when i was a kid

made me laugh to see "no raytracing", then immediate use of the perspective projection which is intersecting points and a plane along a ray lol...

it's boutique hand-derived ray tracing! very different

Deriving the perspective projection equations involves intersecting a ray and the projection plane, but this doesn't magically turn a rasterizer into a raytracer.

Reply on news.ycombinator.com