spinning_ascii_donut.c

/*
 * "Donut math: how donut.c works" blog post by Andy Sloane:
 * https://www.a1k0n.net/2011/07/20/donut-math.html
 * Relevant video: https://www.youtube.com/watch?v=DEqXNfs_HhY
 */

#include <stdio.h>
#include <string.h>
#include <math.h>
#include <unistd.h>

int main() {
  float A = 0, B = 0;
  float i, j;
  int k;
  float z[1760];
  char b[1760];
  printf("");
  for (;;) {
    memset(b, 32, 1760);
    memset(z, 0, 7040);
    for (j = 0; j < 6.28; j += 0.07) {
      for (i = 0; i < 6.28; i += 0.02) {
        float c = sin(i);
        float d = cos(j);
        float e = sin(A);
        float f = sin(j);
        float g = cos(A);
        float h = d + 2;
        float D = 1 / (c * h * e + f * g + 5);
        float l = cos(i);
        float m = cos(B);
        float n = sin(B);
        float t = c * h * g - f * e;
        int x = 40 + 30 * D * (l * h * m - t * n);
        int y = 12 + 15 * D * (l * h * n + t * m);
        int o = x + 80 * y;
        int N = 8 * ((f * e - c * d * g) * m - c * d * e - f * g - l * d * n);
        if (22 > y && y > 0 && x > 0 && 80 > x && D > z[o]) {
          z[o] = D;
          b[o] = ".,-~:;=!*#$@"[N > 0 ? N : 0];
        }
      }
    }
    printf("");
    for (k = 0; k < 1761; k++) {
      putchar(k % 80 ? b[k] : 10);
      A += 0.00004;
      B += 0.00002;
    }
    usleep(30000);
  }
  return 0;
}