Galactic Christmas - OpenProcessing

mySketch
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// Spiral Galaxy Simulation
// author : Philippe Guglielmetti (Dr. Goulu www.goulu.net)
// 2008.04.03 PhG : my first processing program !
//                  converted from my LUA/Demoniak 3D demo V 1.0
//                  see http://3dmon.wordpress.com/2007/08/26/simulation-de-galaxie-spirale/
// 2008.04.04 PhG : much faster in P3D mode : now ok with 10'000 stars !
//                  keyboard interaction : use arrow keys to alter the galaxy
​
window.tr = window.console && console.log.bind( console ) || function(){};
function gauss( x ){  return Math.exp( - x * x / 2 ) / sqrt( 2 * Math.PI );  }
function gaussI( z ){ // integrated gauss [0..1]
  if( z < -8.0 )  return 0.0;
  if( z >  8.0 )  return 1.0;
  var sum = 0, term = z;
  for( var i = 3; sum + term !== sum; i+= 2 ){
    sum  += term;
    term *= z * z / i;
  }
  return 0.5 + sum * gauss(z);
}
function gaussE( z ){  return gaussI( z ) * 2 - 1;  }  // gauss error func==> [-1..0..1]
function randomGauss(){
  var x = 0, y = 0, r, c;
  do{
    x = Math.random() * 2 - 1;
    y = Math.random() * 2 - 1;
    r = x * x + y * y;
  }while( r === 0 || r > 1 );
  c = Math.sqrt( - 2 * Math.log(r) / r );
  return x * c;  //return [x*c, y*c];
}
function randomGaussIn( L, H, mul ){  return constrain( randomGauss() * (H-L) * mul + (L+H) / 2, L, H );  }
function randomGaussAt( L, H, mul ){  return            randomGauss() * (H-L) * mul + (L+H) / 2;  }
​
​
​
var stars = 10000;  // only ...
var Rmax  = 200;    // galaxy radius
var speed = 0.02;   // rotation speed
​
// stars follow elliptic orbits around the center
// var eratio = .85;  // ellipse ratio
// var etwist = 8.0 / Rmax;  // twisting factor (orbit axes depend on radius)
var eratio = 0.8;
var etwist = 0.07;  //rmax=200
​
var angle  = [];
var radius = [];
var z      = [];
​
var WW, HH;
var cx, cy;  //center
var frameTime = 1000 / 60;  // millisec
var pts = Date.now() - frameTime;
​
function windowResized(){
  initCanvas( false );
}
​
function initCanvas( first ){
  WW = Math.min( 900, windowWidth );
  HH = Math.min( 500, windowHeight );
  ( first ? createCanvas : resizeCanvas )( WW, HH );
  background('#000000');  // back to black
  // begin in the center
  cx = WW / 2;
  cy = HH / 2;
}
​
function setup(){
  initCanvas( true );
  // init stars
  for( var i = 0; i < stars; i++ ){
    angle[i]  = Math.random() * 2 * Math.PI;
    radius[i] = Math.abs( randomGauss()) * Rmax * 0.6 + 0.0;    // radius[i] = random( 1, Rmax );
    z[i] = randomGauss() * gauss( radius[i] / Rmax * 5.0 ) * Rmax * 0.04;
    z[i] = Math.abs( z[i]);
    //z[i] = 0;
  }
}
​
​
function draw(){
  /** /
    background( 0, 0, 0, 128 );
  /**/
    var img = get();
    img.resize( Math.round( WW * 0.25 ), Math.round( HH * 0.25 ));
    img.resize( WW - 2, HH - 2 );
    tint( 245, 250, 255 );
    image( img, 1, 1 );
  /**/
​
  var ts = Date.now();
  var dt = ts - pts;
  pts = ts;
  var fps = 1000 / dt;
​
  //var speedMul = speed / getTargetFrameRate();
  var speedMul = speed / fps;
​
  //fill(0,8); rect( 0, 0, WW, HH );
  noStroke();
  var r, a, x, y, b, s, c, xx, yy, dd;
  for( var i = 0; i < stars; i++ ){
    r = radius[i];
    a = angle[i] + speedMul * ( Rmax / r ) * 3;  // increment angle
    angle[i] = a;
    x = r * Math.sin( a );
    y = r * eratio * Math.cos( a );
    b = r * etwist;
    s = Math.sin( b );
    c = Math.cos( b );
    xx = cx +   s*x + c*y;  // a bit of trigo
    yy = cy + ( c*x - s*y ) / 3 - z[i] * 20 + cy * 0.2;
    //dd = ( r - 50.0 ) * 7.0;
    dd = 40000.0 / r;
    fill( dd, dd, dd * 0.9, 32 );
​
    /**/
    if( z[i] > 0.2 ){
      if( z[i] > 9.0 ){
        fill( 255, 255, 255, 255 );
        ellipse( xx, yy, 7, 7 );
        fill( 255, 255, 255, 32 );
      }else if( z[i] > 4.5 ){
        fill( 255, 32, 32, 64 );
        ellipse(xx,yy,7.0,7.0);
        fill( 255, 255, 255, 32 );
      }else if( z[i] > 4.1 ){
        fill( 255, 255, 255, 255 );
        ellipse( xx, yy, 7, 7 );
        fill( 255, 255, 255, 32 );
      }else{
        fill( 80, 128, 40, 64 );
        if(( i % 50 ) === 0 ){
          fill( 255, 255, 255, 255 );
          ellipse( xx, yy, 7, 7 );
          fill( 255, 255, 255, 32 );
        }
      }
    }/**/
​
    rect( xx - 1.5, yy - 1.5, 3, 3 );
  } // for i stars
  if( keyIsPressed )  handleKey();
}
​
function handleKey(){
  if( keyCode === UP_ARROW )     eratio *= 1.02;
  if( keyCode === DOWN_ARROW )   eratio /= 1.02;
  if( keyCode === LEFT_ARROW )   etwist += 0.001;
  if( keyCode === RIGHT_ARROW )  etwist -= 0.001;
}
function keyPressed(){
  handleKey();
}
​