spinel でドーナツらしきもの

donut.rb

a = 0.0
b_rot = 0.0

# Pre-define some constants and arrays
chars = ".,-~:;=!*#$@"
out_buf = ""

# Hide cursor and clear screen
print "\x1b[?25l"
print "\x1b[2J"

while true
  z = Array.new(1760, 0.0)
  b = Array.new(1760, " ")

  j = 0.0
  while j < 6.28
    i = 0.0
    while i < 6.28
      c = Math.sin(i)
      d = Math.cos(j)
      e = Math.sin(a)
      f = Math.sin(j)
      g = Math.cos(a)
      h = d + 2.0
      
      depth_inv = 1.0 / (c * h * e + f * g + 5.0)
      l = Math.cos(i)
      m = Math.cos(b_rot)
      n = Math.sin(b_rot)
      t = c * h * g - f * e

      x = (40.0 + 30.0 * depth_inv * (l * h * m - t * n)).to_i
      y = (12.0 + 15.0 * depth_inv * (l * h * n + t * m)).to_i
      o = x + 80 * y
      
      n_idx = (8.0 * ((f * e - c * d * g) * m - c * d * e - f * g - l * d * n)).to_i

      if 22 > y && y > 0 && x > 0 && 80 > x && depth_inv > z[o]
        z[o] = depth_inv
        idx = n_idx > 0 ? n_idx : 0
        idx = 11 if idx > 11
        b[o] = chars[idx]
      end
      
      i += 0.02
    end
    j += 0.07
  end

  out_buf = "\x1b[H" # Reset cursor to top-left
  k = 0
  while k < 1760
    if k % 80 == 79
      out_buf << 10.chr # newline
    else
      out_buf << b[k]
    end
    k += 1
  end
  print out_buf

  a += 0.004
  b_rot += 0.002
end