From c900d290a3d86a4486ac2a8790de0b89b914c47d Mon Sep 17 00:00:00 2001
From: Yuval Adam <yuv.adm@gmail.com>
Date: Fri, 18 May 2012 11:04:06 +0300
Subject: initial lsys.js import

---
 lsys.js | 143 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 143 insertions(+)
 create mode 100644 lsys.js

diff --git a/lsys.js b/lsys.js
new file mode 100644
index 0000000..de94df3
--- /dev/null
+++ b/lsys.js
@@ -0,0 +1,143 @@
+// L-System as defined in
+// http://en.wikipedia.org/wiki/L-system
+
+// Example usage:
+// lsys = LSystem('F', { 'F' : 'F-F+FF' });
+// tree = lsys.iterate(2)
+
+function LSystem(axiom, rules) {
+  this.axiom = axiom;
+  this.rules = rules;
+  this.tree = axiom;
+
+  this.iterate = function(n) {
+    for (var i=0; i<n; i++) {
+      this.tree = this.tree.replace(/\w/g, function(c) {
+        return rules[c] || c;
+      });
+    }
+    return this.tree;
+  };
+
+  this.draw = function(alpha) {
+    if (alpha === undefined)
+      alpha = 90 * (Math.PI / 180);
+
+    var coords = [];
+    var stack = [];
+    var geometry = [[0,0,0]];
+
+    var x = 0, y = 0, z = 0; // cartesian coordinates
+    var nx = 0, ny = 1, nz = 0; // next step delta
+    var H = 0, L = 0, U = 0; // headings on 3 axes
+    var RUu = false, RLu = false, RHu = false;
+
+    for (var i=0; i<this.tree.length; i++) {
+      var c = this.tree.charAt(i);
+      switch(c) {
+        case '+':
+          U += alpha;
+          RUu = true;
+          break;
+        case '-':
+          U -= alpha;
+          RUu = true;
+          break;
+
+        case '&':
+          L += alpha;
+          RLu = true;
+          break;
+        case '^':
+          L -= alpha;
+          RLu = true;
+          break;
+
+        case '<':
+          H += alpha;
+          RHu = true;
+          break;
+        case '>':
+          H -= alpha;
+          RHu = true;
+          break;
+
+        case '|':
+          U += Math.PI / 2;
+          RUu = true;
+          break;
+        // push and pop branch
+        case '[':
+          stack.push(x, y, z, H, L, U, geometry);
+          geometry = [[x,y,z]];
+          break;
+        case ']':
+          coords.push(geometry);
+          geometry = stack.pop();
+          U = stack.pop();
+          L = stack.pop();
+          H = stack.pop();
+          z = stack.pop();
+          y = stack.pop();
+          x = stack.pop();
+          break;
+        // forward draw
+        case 'F':
+          nx = 0, ny = 1, nz = 0;
+          nc = this.tree.charAt(i+1);
+
+          if (RUu) {
+            var tx = (nx * Math.cos(U)) - (ny * Math.sin(U));
+            var ty = (nx * Math.sin(U)) + (ny * Math.cos(U));
+            nx = tx;
+            ny = ty;
+
+            if (nc != 'F')
+              RUu = false;
+          }
+
+          if (RLu) {
+            var tx = (nx * Math.cos(L)) + (nz * Math.sin(L));
+            var tz = -(nx * Math.sin(L)) + (nz * Math.cos(L));
+            nx = tx;
+            nz = tz;
+
+            if (nc != 'F')
+              RLu = false;
+          }
+
+          if (RHu) {
+            var ty = (ny * Math.cos(H)) + (nz * Math.sin(H));
+            var tz = -(ny * Math.sin(H)) + (nz * Math.cos(H));
+            ny = ty;
+            nz = tz;
+
+            if (nc != 'F')
+              RHu = false;
+          }
+
+          x += nx;
+          y += ny;
+          z += nz;
+          
+          geometry.push([x,y,z]);
+          break;
+      }
+    }
+
+    coords.push(geometry);
+    return coords;
+  };
+
+  this.reset = function() {
+    this.tree = axiom;
+    return this.tree;
+  };
+
+  this.debug = function() {
+    console.log('Axiom: ' + this.axiom);
+    console.log('Rules: ' + this.rules);
+    console.log('Tree: ' + this.tree);
+  };
+
+}
-- 
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