From e81c764bd50ba3e0b34b3138078af0a372242988 Mon Sep 17 00:00:00 2001
From: Akshay Nair <phenax5@gmail.com>
Date: Sat, 18 Nov 2023 14:58:24 +0530
Subject: feat: dragon fractal

---
 TODO.norg              | 13 ++++++-----
 flake.nix              |  1 +
 justfile               | 10 +++++----
 sketches/05/dragon.rkt | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 75 insertions(+), 9 deletions(-)
 create mode 100644 sketches/05/dragon.rkt

diff --git a/TODO.norg b/TODO.norg
index 28d69d4..c514b0f 100644
--- a/TODO.norg
+++ b/TODO.norg
@@ -2,22 +2,25 @@
   - (x) Mandelbrot | BQN + Glsl
   - (x) Newton's fractals | Glsl
   - ( ) Flow | Glsl
-  - ( ) {http://quil.info/sketches/local/04058d1f6e2628d8c71b4fd7c850b8937c0d12b8c48cfb2383b24fbdf41ae8c1} | Glsl
+  - (x) polka | Glsl
+  - ( ) Dragon deez nuts | Racket
 
 * Ideas
-  - Flow fields on image
+  - Dragon fractal
   - Newton's fractals
-  - Iterate over messytones
-  - Spinning poin
   - Mandelbrot
-  - Buddhabrot
+  - Flow fields on image
+  - Iterate over messytones
+  - Spinning poin (Future me note: what?)
   - Siperski triangle
   - 3d game of life
   - Webcam effects
   - Hilbert curve
+  - Polynomial fractals? {https://frankwang95.github.io/2018/02/polynomial-roots-are-beautiful}
 
 * Tools
   - HTML5 canvas
+  - Sketching racket {https://docs.racket-lang.org/manual-sketching/Reference.html#%28part._loop%29}
   - p5.js
   - Uiua
   - {https://github.com/sleexyz/hylogen}
diff --git a/flake.nix b/flake.nix
index 50d3c9a..256d081 100644
--- a/flake.nix
+++ b/flake.nix
@@ -18,6 +18,7 @@
             uiua
             glslviewer
             nodePackages.live-server
+            racket
             # cbqn
           ];
         };
diff --git a/justfile b/justfile
index 2d1f299..915a277 100644
--- a/justfile
+++ b/justfile
@@ -3,12 +3,14 @@ sketch name *args:
 
 s1: (sketch "01" "glslViewer" "mandelbrot.frag")
 s1_bqn: (sketch "01" "live-server" "--port=3000" "--no-browser" ".")
+
 s2: (sketch "02" "glslViewer" "newton.frag")
-s3: (sketch "03" "glslViewer" "flow.frag" "-testImage" "test.png")
-s4: (sketch "04" "glslViewer" "polka.frag")
 
+s3: (sketch "03" "glslViewer" "flow.frag" "-testImage" "test.png")
 
-# week1:
-#   npx nodemon -e ua -x 'clear && just sketch week1 uiua run --no-format'
+s4: (sketch "04" "glslViewer" "polka.frag")
 
+s5_run: (sketch "05" "racket" "dragon.rkt")
+s5:
+  npx nodemon -e rkt -x 'clear && just s5_run'
 
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)))))
+
-- 
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