Bresenham Circle in DragonRuby

main.rb

# Bresenham circle for DragonRuby (basic)

RED = [255, 0, 0]

def put_pixel(args, x, y, c)
  args.outputs.solids << [x, y, 1, 1, *c]
end

def drawCircle(args, xc, yc, x, y)
  put_pixel(args, xc + x, yc + y, RED)
  put_pixel(args, xc - x, yc + y, RED)
  put_pixel(args, xc + x, yc - y, RED)
  put_pixel(args, xc - x, yc - y, RED)
  put_pixel(args, xc + y, yc + x, RED)
  put_pixel(args, xc - y, yc + x, RED)
  put_pixel(args, xc + y, yc - x, RED)
  put_pixel(args, xc - y, yc - x, RED)
end
  
# circle-generation using Bresenham's algorithm
def circleBres(args, xc, yc, r)
  x = 0
  y = r
  d = 3 - (2 * r)
  drawCircle(args, xc, yc, x, y)
  while y >= x
    if d.positive?
      y -= 1
      d = d + 4 * (x - y) + 10
    else
      d = d + (4 * x) + 6
    end
    x += 1
    drawCircle(args, xc, yc, x, y)
  end
end

def tick(args)
  xc = 640 # x centre
  yc = 360 # y centre
  r = 100  # radius
  circleBres(args, xc, yc, r)
end