Tributary inlet

config.json

{"description":"Tributary inlet","endpoint":"","display":"canvas","public":true,"require":[],"fileconfigs":{"inlet.js":{"default":true,"vim":false,"emacs":false,"fontSize":12}},"fullscreen":false,"play":true,"loop":false,"restart":false,"autoinit":true,"pause":true,"loop_type":"pingpong","bv":false,"nclones":15,"clone_opacity":0.4,"duration":3000,"ease":"linear","dt":0.01,"ajax-caching":true,"thumbnail":"http://i.imgur.com/BXjWAar.png"}

inlet.js

//laser math 
//http://spot.colorado.edu/~lessley/pdf%20stuff/lasermath2.pdf
//http://spot.colorado.edu/~lessley/rosecurves.html

var x0 = 450;
var y0 = 288;
  
var n = 55;
//main parameters, ratio matters
var a = 6.4512 * n;
var b = -2 * n;
//var b = (n-1)/(n+10);

//x tilt? (x radius)
var hx = 498;
//y tilt? (y radius)
var hy = 4;

//frequency, adjust fbase
var fbase = 58.2568;
var omega0 = 2 * Math.PI * fbase;

//slow down or speed up the tracers
var om = omega0 * 0.03755;

//how fast it fades
var erasing = 0.05;
//number of points in the paths (more = smoother)
var linen = 300;

//color of the paths
var cs = d3.interpolateHsl("#3300FF", "#093335");
var sopacity = 1;
//color of the tracers
var cf = d3.interpolateHsl("#A80014", "#000424");
var fopacity = 0.7;
//radius of the tracers
var radius = 1;
// number of tracers
var nt = 413;
//time offset for each tracer
var to = 0.4712;

function x(t, o) {
  //return (a - b) * Math.cos(omega0*t) + h * Math.cos(omega0*t*(a/b-1));
  return (a - b) * Math.cos(o*t) + hx * Math.cos(o*t*(a-b)/b);
  //return h * Math.cos(t*Math.PI);
}
function y(t, o) {
  //return (a - b) * Math.sin(omega0*t) - h * Math.sin(omega0*t*(a/b-1));
  return (a - b) * Math.sin(o*t) - hy * Math.sin(o*t*(a-b)/b);
  //return h * Math.sin(t*Math.PI);
}

function circle(ctx, p) {
    //ctx.fillStyle = 'hsla(0,0%,' + 70 +'%,' + 1 + ')';
    ctx.beginPath();
    ctx.arc(p[0],p[1],radius,0,2*Math.PI);
    ctx.fill();
}
function line(ctx) {  
  ctx.beginPath();
  var i;
  for(i=0;i<linen;i++) {
      //ctx.strokeStyle = c(i/linen);
	  ctx.lineTo(x0 + x(i/linen, omega0), y0 + y(i/linen, omega0));
  }
  ctx.stroke();
  
}

tributary.init = function(ctx) {
  d3.select("#display").style("background-color", "#000000")
	ctx.globalCompositeOperation = 'source-over';
  
};
tributary.run = function(ctx,t) {
    //tributary.clear(); //helper function to clear the canvas 
    ctx.fillStyle = "rgba(9,9,9," + erasing +  ")";
    ctx.fillRect(0,0,tributary.sw,tributary.sh);
    var tt = Math.cos(t)/2;
    
    var p;

    ctx.strokeStyle = cs(tt);
	line(ctx);
    
  	p = [x0 + x(tt, om), y0 + y(tt, om)]; 
    ctx.fillStyle = cf(tt);
  	circle(ctx, p);
  
  	
  	var i = 0;
    for(i = 0; i < nt; i++) {
      //p = [x0 + x(tt+i*tt/2, om), y0 + y(tt+i*tt/2, om)]; 
      p = [x0 + x(tt+i*to, om), y0 + y(tt+i*to, om)]; 
      ctx.fillStyle = cf(tt);
  	  circle(ctx, p);
    }
    
  
};