From 24f263a2ca56336b7c18d0a5d9842b8afdef087b Mon Sep 17 00:00:00 2001
From: Frederic <frederic@git.blinkenbunt.org>
Date: Sat, 1 Jun 2019 17:26:52 +0200
Subject: [PATCH] add barnsley fern

---
 lindenmayer-system/lindenmeyer-system.html | 40 ++++++++++++++++++
 lindenmayer-system/lindenmeyer-system.js   | 49 ++++++++++++++++------
 2 files changed, 77 insertions(+), 12 deletions(-)

diff --git a/lindenmayer-system/lindenmeyer-system.html b/lindenmayer-system/lindenmeyer-system.html
index a7b6031..2ac8774 100644
--- a/lindenmayer-system/lindenmeyer-system.html
+++ b/lindenmayer-system/lindenmeyer-system.html
@@ -129,6 +129,40 @@ function sierpinski() {
 }
 
 
+ /************************************************
+  * Barnsley Fern
+  ************************************************/
+
+ function barnsley_fern() {
+     project.clear();
+     var r = generate(
+         'IXF'.split(''),
+         [
+             ['X'.split(''), 'F+[[X]-X]-F[-FX]+X'.split('')],
+             ['F'.split(''), 'FF'.split('')]
+         ],
+         6
+     );
+
+     console.log(r);
+     var p = draw(
+         r,
+         {
+             'F': draw_forward(),
+             'I': draw_angle_init(25/180 * Math.PI),
+             '-': draw_angle_turn(-1),
+             '+': draw_angle_turn(1),
+             '[': draw_state_push(),
+             ']': draw_state_pop()
+         }
+     );
+     p.scale(2);
+     p.translate(new Point(200, 200));
+     p.strokeWidth = 1;
+     p.strokeColor = '#ff00ff';
+ }
+
+
 /************************************************
  * 
  ************************************************/
@@ -136,6 +170,7 @@ function sierpinski() {
 globals.dragon_curve = dragon_curve;
 globals.sierpinski2 = sierpinski2;
 globals.sierpinski = sierpinski;
+globals.barnsley_fern = barnsley_fern;
 
 globals.get_svg = function() {
     return project.exportSVG({asString: true});
@@ -185,6 +220,10 @@ window.onload = function() {
         window.globals.sierpinski();
     });
 
+    document.getElementById('barnsley_fern').addEventListener('click', function() {
+        window.globals.barnsley_fern();
+    });
+
 }
 </script>
 
@@ -196,6 +235,7 @@ window.onload = function() {
 <button id="sierpinski2">sierpinski2</button>
 <button id="sierpinski2-defects">sierpinski2 (random defects)</button>
 <button id="sierpinski">sierpinski</button>
+<button id="barnsley_fern">barnsley_fern</button>
 <hr>
 <canvas id="canvas"  style="width: 500px; height: 500px;" resize></canvas>
 </body>
diff --git a/lindenmayer-system/lindenmeyer-system.js b/lindenmayer-system/lindenmeyer-system.js
index d7e5961..aaee5f3 100644
--- a/lindenmayer-system/lindenmeyer-system.js
+++ b/lindenmayer-system/lindenmeyer-system.js
@@ -43,25 +43,26 @@ function generate(start, rules, iterations) {
 }
 
 
-function draw_initstate(state) {
+function draw_initstate(p, state) {
     if(!('dir' in state)) {
         state.dir = 0;//Math.PI/2;
     }
+    if(!('curpath' in state)) {
+        p.addChild(new paper.Path());
+        state.curpath = p.lastChild;
+    }
 }
 
 
 function draw_forward() {
     return function(p, state) {
-        draw_initstate(state);
-        if(p.children.length == 0) {
-            p.addChild(new paper.Path());
-        }
-        var pp = p.lastChild;
-        if(pp.length == 0) {
-            pp.add(new paper.Point(0, 0));
+        draw_initstate(p, state);
+        if(state.curpath.segments.length == 0) {
+            state.curpath.add(new paper.Point(0, 0));
+            console.log('---------------------------');
         }
-        var lastp = pp.segments[pp.segments.length - 1].point;
-        pp.add(lastp.add(
+        var lastp = state.curpath.segments[state.curpath.segments.length - 1].point;
+        state.curpath.add(lastp.add(
             new paper.Point(Math.sin(state.dir), Math.cos(state.dir))
         ));
     }
@@ -70,7 +71,7 @@ function draw_forward() {
 
 function draw_turn(angle) {
     return function(p, state) {
-        draw_initstate(state);
+        draw_initstate(p, state);
         state.dir += angle;
     }
 }
@@ -78,7 +79,7 @@ function draw_turn(angle) {
 
 function draw_angle_turn(fac) {
     return function(p, state) {
-        draw_initstate(state);
+        draw_initstate(p, state);
         state.dir += state.angle * fac;
     }
 }
@@ -98,6 +99,30 @@ function draw_angle_add(delta) {
 }
 
 
+function draw_state_push() {
+    return function(p, state) {
+        if(typeof state.stack == 'undefined') {
+            state.stack = new Array();
+        }
+        state.stack.push({
+            pos: state.curpath.segments[state.curpath.segments.length - 1].point,
+            dir: state.dir,
+        });
+    }
+}
+
+
+function draw_state_pop() {
+    return function(p, state) {
+        var s = state.stack.pop();
+        state.dir = s.dir;
+        p.addChild(new paper.Path());
+        state.curpath = p.lastChild;
+        state.curpath.add(s.pos);
+    }
+}
+
+
 function draw(word, actions) {
     var p = new paper.CompoundPath();
     var state = {};