SOURCE

/*****************************************************************************
The MIT License (MIT)

Copyright (c) 2014 Andi Smithers

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
*****************************************************************************/

// conceptualized and written by andi smithers

// constant options
const focalDepth = 80;
const focalPoint = 256;


// variables
var centreX;
var centreY;
var mouseX;
var mouseY;
var spawnX;
var spawnY;
var frameCount=0;

// variables
const maxpoints = 4096;
var pointcloud = [];

// uniform distribution of a randomized unit vector
function RandomNormal()
{
  var theta = Math.random() * Math.PI * 2;
  var nz = 1 - 2*Math.random();
  var phi = Math.acos(nz);
  var nx = Math.sin(theta)*Math.sin(phi);
  var ny = Math.cos(theta)*Math.sin(phi);
  
  return {x:nx, y:ny, z:nz};
}

function InitRandomDistribution()
{
   for (var i=0; i<maxpoints;i++)
   {
       pointcloud.push(RandomNormal());
   }
}

var theta = 0;
var phi = 0;
function RenderRandomDistribution()
{ 
    theta+=0.01;
    phi+=0.01;
    var scale = 20* canvas.height/500;
    context.beginPath();
    for (var i=0; i<pointcloud.length; i++)
    {
        var point = pointcloud[i];
      
        var x1 = point.x * Math.cos(theta) - point.z*Math.sin(theta);
        var z1 = point.x * Math.sin(theta) + point.z*Math.cos(theta);
        var y1 = point.y * Math.cos(phi) - z1*Math.sin(phi);
        var z1 = point.y * Math.sin(phi) + z1*Math.cos(phi);
        x1*=scale;
        z1*=scale;
        y1*=scale;
        if (z1+focalDepth<0) continue;
        var depth = focalPoint*3 / (z1 + focalDepth );
    
        var x = x1 * depth + centreX;
        var y = y1 * depth + centreY;
        var sz = depth * 0.2;

        // fill a rect
        context.rect(x,y, sz, sz);
    }
  
    context.fillStyle = '#ffffff';
    context.fill();
}

// initialization

function init()
{
  // setup canvas and context
canvas = document.getElementById('uniform distribution');
context = canvas.getContext('2d');
  
  // set canvas to be window dimensions
  resize();

  // create event listeners
  canvas.addEventListener('mousemove', mouseMove);
  canvas.addEventListener('click', mouseClick);
  window.addEventListener('resize', resize);

  // initialze variables  
  InitRandomDistribution();
}


// input functions

function mouseMove(event) 
{
var rect = canvas.getBoundingClientRect();

mouseX = event.clientX - rect.left,
mouseY = event.clientY - rect.top
}

function mouseClick()
{
}

function resize()
{
  canvas.width = window.innerWidth;
  canvas.height = window.innerHeight;
    // compute centre of screen
  centreX = canvas.width/2;
  centreY = canvas.height/2;
}


// rendering functions

function render()
{
 
  context.fillStyle = 'black';
  context.clearRect(0, 0, canvas.width, canvas.height); 
  
  RenderRandomDistribution();
  
  context.globalAlpha = 1.0;
  context.font = '20pt Calibri';
  context.fillStyle = 'rgb(255,255,255)';
  context.textAlign = "center";
  context.fillText('可爱的球', canvas.width/2, 25); 
}

// movement functions

function update()
{ 
}

// per frame tick functions

function animate()
{
  frameCount++;
  // movement update
  update();
  // render update
  render();
  // trigger next frame
  requestAnimationFrame(animate);
}



// entry point
init();
animate();</script>

<canvas id='uniform distribution' ></canvas>

body {
  background: #000000;
  margin: 0px;
  padding: 0px;
}