Added simple raytracer example

.gitignore

@@ -4,3 +4,4 @@ build
 test/images/*.png
 examples/*.png
 testing
+test.png

examples/ray.js

@@ -0,0 +1,83 @@
+
+/**
+ * Module dependencies.
+ */
+
+var Canvas = require('../lib/canvas')
+  , canvas = new Canvas(1150, 230) 
+  , ctx = canvas.getContext('2d')
+  , fs = require('fs');
+
+
+function render(level){
+  renderLevel(level,81,0);
+}
+
+function renderLevel(minimumLevel,level,y){
+  for (var x=0; x < 243 / level; ++x) {
+    drawBlock(x,y,level);
+  }
+  for (var x=0; x < 243 / level; x+=3){
+    drawBlock(x,y+1,level);
+    drawBlock(x+2,y+1,level);
+  }
+  for (var x=0; x < 243 / level; ++x){
+    drawBlock(x,y+2,level);
+  }
+  if ((y += 3) >= 243 / level){
+    y=0;
+    level /= 3;
+  }
+  if (level >= minimumLevel){
+    renderLevel(minimumLevel, level, y);
+  }
+}
+
+function drawBlock(x,y,level){
+  ctx.fillStyle = getPointColour(
+      x * level + (level-1) / 2
+    , y * level + (level-1) / 2);
+
+  ctx.fillRect(
+      x * level
+    , y * level
+    , level
+    , level
+    );
+}
+
+function getPointColour(x,y){
+  x= x / 121.5 - 1;
+  y= -y / 121.5 + 1;
+  var x2y2 = x * x + y * y;
+  if (x2y2 > 1){
+    return '#000';
+  } else {
+    var root = Math.sqrt(1 - x2y2);
+    var x3d = x * 0.7071067812 + root / 2 - y / 2;
+    var y3d = x * 0.7071067812 - root / 2 + y / 2;
+    var z3d = 0.7071067812 * root + 0.7071067812 * y;
+    var brightness= -x / 2 + root * 0.7071067812 + y / 2;
+    if (brightness < 0) brightness = 0;
+    return ''
+      + 'rgb(' + Math.round(brightness * 127.5 * (1 - y3d))
+      + ',' + Math.round(brightness * 127.5 * (x3d + 1))
+      + ',' + Math.round(brightness * 127.5 * (z3d + 1))
+      + ')'
+      ;
+ }
+}
+
+var start = new Date;
+render(15);
+ctx.translate(230,0);
+render(10);
+ctx.translate(230,0);
+render(6);    
+ctx.translate(230,0);
+render(3);    
+ctx.translate(230,0);
+render(1);
+console.log('Rendered in %d seconds', (new Date - start) / 1000);
+
+canvas.savePNG(__dirname + "/ray.png");