bool rayHitsAABB(vec3f a, vec3f b, vec3f pos, vec3f dir) {
  for int i <- 0..3
    if (dir[i] < 0) { float _o = a[i]; a[i] = -b[i]; b[i] = -_o; pos[i] = -pos[i]; dir[i] = -dir[i]; }

  // pretend ray starts at origin
  a -= pos;
  b -= pos;
  if (b.x < 0 || b.y < 0 || b.z < 0) return false; // ray is pointed away from aabb.
  // multiply every component with dir.(x*y*z)
  // vec3f dista = a / dir, distb = b / dir;
  vec3f mulfac = vec3f(dir.(y * z, x * z, x * y));
  vec3f dista = a * mulfac, distb = b * mulfac;

  float entry = max(dista.x, max(dista.y, dista.z));
  float exit = min(distb.x, min(distb.y, distb.z));
  if (entry <= exit) return true;
  return false;
}