brownian.lisp

;;;; brownian.lisp

(in-package #:sketch-examples)

;;  ____  ____   _____        ___   _ ___    _    _   _
;; | __ )|  _ \ / _ \ \      / / \ | |_ _|  / \  | \ | |
;; |  _ \| |_) | | | \ \ /\ / /|  \| || |  / _ \ |  \| |
;; | |_) |  _ <| |_| |\ V  V / | |\  || | / ___ \| |\  |
;; |____/|_| \_\\___/  \_/\_/  |_| \_|___/_/   \_\_| \_|

(defsketch brownian
    ((title "Brownian")
     (width 800)
     (height 600)
     (copy-pixels t)
     (pos (cons (/ width 2) (/ height 2))) (dir '(1 . 0))
     (pen (make-pen :stroke (gray 0.5) :fill (gray 0.5) :weight 1))
     (line-length 3)
     (points (make-array 256 :initial-element (cons 400 300)))
     (points-pointer 0))
  (flet ((draw (paces)
           (dotimes (i paces)
             (let ((new-pos (cons (+ (car pos) (car dir))
                                  (+ (cdr pos) (cdr dir)))))
               (with-pen pen
                 (line (car pos) (cdr pos) (car new-pos) (cdr new-pos)))
               (setf pos new-pos))))
         (rotate (a)
           (let ((a (+ a (degrees (atan (cdr dir) (car dir))))))
             (setf dir (cons (cos (radians a))
                             (sin (radians a)))))))
    (rotate (- (random 180) 90))
    (draw (+ (random line-length) line-length))
    (setf (car pos) (alexandria:clamp (car pos) -10 810)
          (cdr pos) (alexandria:clamp (cdr pos) -10 610))))

(defmethod setup ((instance brownian) &key &allow-other-keys)
  (background (gray 1)))