feat: dragon fractal

1 files changed, 60 insertions, 0 deletions

diff --git a/sketches/05/dragon.rkt b/sketches/05/dragon.rkt
new file mode 100644
index 0000000..9cca295
--- /dev/null
+++ b/sketches/05/dragon.rkt
@@ -0,0 +1,60 @@
+#lang sketching
+
+(define (setup)
+  (size 200 200)
+  (frame-rate 1)
+  (loop))
+
+(define iterations 14)
+(define init-segment 400)
+
+(define Line cons)
+(define ->0 car)
+(define ->1 cdr)
+(define Point cons)
+(define ->x car)
+(define ->y cdr)
+
+(define (draw/line my-line)
+  (let [ (p1 (->0 my-line)) (p2 (->1 my-line)) ]
+    (line (->x p1) (->y p1) (->x p2) (->y p2))))
+
+(define (split-line my-line dir)
+  (let* [
+         (x1 (->x (->0 my-line)))
+         (y1 (->y (->0 my-line)))
+         (x2 (->x (->1 my-line)))
+         (y2 (->y (->1 my-line)))
+         (len (dist x1 y1 x2 y2))
+         (sidelen (sqrt (/ (* len len) 2)))
+         (theta (atan2 (- y2 y1) (- x2 x1)))
+         (slope (+ theta (* (/ pi 4) dir)))
+         (p3 (Point
+              (+ x1 (* sidelen (cos slope)))
+              (+ y1 (* sidelen (sin slope)))))
+         ]
+    (cons (Line (->0 my-line) p3) (Line p3 (->1 my-line)))))
+
+(define (dragon-curve my-line dir iteration)
+  (let [ (lines (split-line my-line dir)) ]
+    (if (<= iteration 0)
+        (list (->0 lines) (->1 lines))
+        (append
+         (dragon-curve (->0 lines) 1 (- iteration 1))
+         (dragon-curve (->1 lines) -1 (- iteration 1))))))
+
+(define current-iteration 0)
+(define (draw)
+  (background 150)
+  (let* [
+         (p1 (Point (- (/ width 2) (/ init-segment 2)) (/ height 2)))
+         (l1 (Line p1 (Point (+ (->x p1) init-segment) (->y p1))))
+         (lines (dragon-curve l1 1 current-iteration))
+         ]
+    (stroke-weight 2)
+    (stroke 0 0 0)
+    (for-each draw/line lines)
+    (if (= current-iteration iterations)
+        (no-loop)
+        (set! current-iteration (+ current-iteration 1)))))
+