Last week I sat down to see how I can generate a fractal tree on a web page. It turned out to be a very interesting exercise using HTML5 Canvas and simple Math trigonometric functions. Using random numbers for changing the length of the tree branch, and the angle of branch split -- I was quite successful in generating very realistic looking trees!
Each time you render the HTML, the trees look quite different. I can see how Game creators can create interesting looking forests for "heroes" to travel in using such techniques.
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| HTML 5 Canvas with a Fractal Tree |
Here is the code (also posted on github):
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| <html> | |
| <head> | |
| <script type="text/javascript"> | |
| window.onload = draw; | |
| function draw(){ | |
| var canvas = document.getElementById('myCanvas'); | |
| if (canvas.getContext){ | |
| var context = canvas.getContext('2d'); | |
| drawFractalTree(context); | |
| } | |
| else{ | |
| alert("HTML5 Canvas isn't supported by your browser!"); | |
| } | |
| } | |
| function drawFractalTree(context){ | |
| drawTree(context, 800, 800, -90, 11); | |
| } | |
| function drawTree(context, x1, y1, angle, depth){ | |
| var BRANCH_LENGTH = random(0, 20); | |
| if (depth != 0){ | |
| var x2 = x1 + (cos(angle) * depth * BRANCH_LENGTH); | |
| var y2 = y1 + (sin(angle) * depth * BRANCH_LENGTH); | |
| drawLine(context, x1, y1, x2, y2, depth); | |
| drawTree(context, x2, y2, angle - random(15,20), depth - 1); | |
| drawTree(context, x2, y2, angle + random(15,20), depth - 1); | |
| } | |
| } | |
| function drawLine(context, x1, y1, x2, y2, thickness){ | |
| context.fillStyle = '#000'; | |
| if(thickness > 6) | |
| context.strokeStyle = 'rgb(139,126, 102)'; //Brown | |
| else | |
| context.strokeStyle = 'rgb(34,139,34)'; //Green | |
| context.lineWidth = thickness * 1.5; | |
| context.beginPath(); | |
| context.moveTo(x1,y1); | |
| context.lineTo(x2, y2); | |
| context.closePath(); | |
| context.stroke(); | |
| } | |
| function cos (angle) { | |
| return Math.cos(deg_to_rad(angle)); | |
| } | |
| function sin (angle) { | |
| return Math.sin(deg_to_rad(angle)); | |
| } | |
| function deg_to_rad(angle){ | |
| return angle*(Math.PI/180.0); | |
| } | |
| function random(min, max){ | |
| return min + Math.floor(Math.random()*(max+1-min)); | |
| } | |
| </script> | |
| <style type="text/css"> | |
| canvas { border: 1px solid white; } | |
| </style> | |
| </head> | |
| <body> | |
| <canvas id="myCanvas" width="1500" height="800"></canvas> | |
| </body> | |
| </html> |
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