Created
September 24, 2012 12:25
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Function#fork parallel shading
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| <!DOCTYPE html> | |
| <html lang="en"> | |
| <head> | |
| <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> | |
| </head> | |
| <body> | |
| <script> | |
| Function.prototype.fork = function (cb, thisArg) { | |
| var args = [].slice.call(arguments, 2) | |
| var fn = this | |
| setTimeout(function () { | |
| try { | |
| cb(null, fn.apply(thisArg, args)) | |
| } catch (e) { | |
| cb(e) | |
| } | |
| }, 0) | |
| } | |
| </script> | |
| <canvas id="c"></canvas> | |
| <script src="shade.js"> | |
| </script> | |
| </body> | |
| </html> |
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| /*jshint asi:true, esnext:true */ | |
| void function () { | |
| const SHADER_COUNT = 4 | |
| const WIDTH = 400 | |
| const HEIGHT = 400 | |
| function shader (d) { | |
| var i, n, x, y, a | |
| var xf = 2 / d.w | |
| var yf = 2 / d.w / d.h | |
| var img = d.data | |
| var l = img.length | |
| var f = d.f | |
| for (i=0, n=d.s/4; i<l; i+=4, n++) { | |
| x = (n % d.w) * xf - 1.0 | |
| y = n * yf - 1.0 | |
| a = Math.abs(Math.sin(Math.atan2(x, y) + f * 0.02)) | |
| img[i+0] = 255 * Math.abs(x) * a | |
| img[i+1] = 255 * Math.abs(y) * (1.0 - a) | |
| img[i+2] = 255 * Math.sqrt(Math.abs(x * y)) | |
| img[i+3] = 255 | |
| } | |
| f += 1 | |
| return d.id | |
| } | |
| function copies (l, cb) { | |
| var i, r = Array(l) | |
| for (i=0; i<l; i++) { | |
| r[i] = cb(i) | |
| } | |
| return r | |
| } | |
| var rAF = | |
| window.requestAnimationFrame || | |
| window.webkitRequestAnimationFrame || | |
| window.mozRequestAnimationFrame || | |
| window.oRequestAnimationFrame || | |
| window.msRequestAnimationFrame || | |
| function (cb) { | |
| return window.setTimeout(cb, 1000 / 60) | |
| } | |
| function onComplete (err, id) { | |
| if (err) throw err | |
| readyStates[id] = true | |
| if (readyStates.filter(function (s) { | |
| return !!s | |
| }).length === readyStates.length) { | |
| rAF(draw) | |
| } | |
| } | |
| var c = document.getElementById('c') | |
| var w = c.width = WIDTH | |
| var h = c.height = HEIGHT | |
| var f = 0 | |
| var ctx = c.getContext('2d') | |
| var iD = ctx.getImageData(0, 0, w, h) | |
| var rT, img | |
| var readyStates = copies(SHADER_COUNT, function () { | |
| return false | |
| }) | |
| function draw () { | |
| var i, n, m | |
| iD.data.set(img) | |
| ctx.putImageData(iD, 0, 0) | |
| parallelize() | |
| } | |
| function parallelize () { | |
| var i, s | |
| var l = ~~(iD.data.length / SHADER_COUNT / 4) * 4 | |
| if (!img || img.length !== iD.data.length) { | |
| img = new Uint8Array(iD.data.length) | |
| } | |
| for (i=0, s=0; i < SHADER_COUNT-1; i++, s+=l) { | |
| readyStates[i] = false | |
| shader.fork(onComplete, null, { | |
| id: i, | |
| w: w, | |
| h: h, | |
| s: s, | |
| f: f, | |
| data: img.subarray(s, s + l) | |
| }) | |
| } | |
| readyStates[i] = false | |
| shader.fork(onComplete, null, { | |
| id: i, | |
| w: w, | |
| h: h, | |
| s: s, | |
| f: f, | |
| data: img.subarray(s) | |
| }) | |
| rT = +new Date() | |
| f += 1 | |
| } | |
| /* start the weird async loop */ | |
| parallelize() | |
| }() |
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