node-canvas/examples/ray.js

/**
 * Module dependencies.
 */

var Canvas = require('../lib/canvas')
  , canvas = new Canvas(243 * 4, 243) 
  , ctx = canvas.getContext('2d')
  , fs = require('fs');

function render(level){
  ctx.fillStyle = getPointColour(122,122);
  ctx.fillRect(0,0,240,240);
  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(10);
ctx.translate(243,0);
render(6);    
ctx.translate(243,0);
render(3);    
ctx.translate(243,0);
render(1);
console.log('Rendered in %s seconds', (new Date - start) / 1000);

canvas.toBuffer(function(err, buf){
  if (err) throw err;
  fs.writeFile(__dirname + '/ray.png', buf);
});