blinsay/README.md

## README.md

      
    Raw
  

              README.md
            
          
    Gradient descent on 2d Perlin noise. Inspired by and forked from d2fn

  
## index.html
<!DOCTYPE html>
<meta charset="utf-8">
<style>

    body {
    background: rgb(255, 255, 255);
    }

</style>
<body>
<script src="http://d3js.org/d3.v3.min.js"></script>
<script src="/d2fn/raw/8777d620caef32959713/perlin.js"></script>
<script>

var width = 960,
    height = 500,
    noiseScale = 0.003,
    actorStepLength = 1000,
    numActors = 10000,
    step = 0,
    steps = 150,
    gradientEpsilon = noiseScale / 100.0;

var canvas = d3.select("body")
    .append("canvas")
    .attr({width: width, height: height});

var context = canvas.node().getContext("2d");
context.fillStyle = "rgb(0, 0, 0)";
context.fillRect(-1, -1, width, height);

var actors = [];
for(var i = 0; i < numActors; i++) {
    actors.push(actor(width, height, noiseScale, actorStepLength));
}

var opacity = easeInOut(steps);

d3.timer(function() {
    if(++step > steps) {
        console.log("done with animation");
        return true;
    }
    context.lineWidth = 1;
    context.globalCompositeOperation = 'lighter';
    context.beginPath();
    for(var i in actors) {
        var a = actors[i];
        var ln = a.step();
        var alpha = 0.6*opacity.get();
        context.strokeStyle = "rgba(49, 130, 189, " + alpha + ")";
        context.moveTo(ln.x1, ln.y1);
        context.lineTo(ln.x2, ln.y2);
    }
    context.stroke();
    opacity.step();
});

function actor(width, height, noiseScale, stepLength) {

    var x = Math.random() * width,
        y = Math.random() * height;

    var noise = perlin.noise(noiseScale);

    return {
        // get the last point and the next point
        step: function() {
            var x1 = x,
                y1 = y,
                grad = approximateGradient(noise, x, y, gradientEpsilon);
            x = x + stepLength * (-1 * grad.x),
            y = y + stepLength * (-1 * grad.y);
            return {
                x1: x1,
                y1: y1,
                x2: x,
                y2: y
            }
        }
    }
}

function easeInOut(steps) {
    var n = 0;
    var val = 0;
    return {
        step:
            function() {
                val = 0.075*(1-Math.cos(2 * Math.PI * (n++) / steps));
            },
        get:
            function() {
                return val;
            }
    };
}

function approximateGradient(f, x, y, h) {
  return {
    x: (f(x + h, y) - f(x - h, y)) / (2*h),
    y: (f(x, y + h) - f(x, y - h)) / (2*h)
  }
}

</script>
	<!DOCTYPE html>
	<meta charset="utf-8">
	<style>

	body {
	background: rgb(255, 255, 255);
	}

	</style>
	<body>
	<script src="http://d3js.org/d3.v3.min.js"></script>
	<script src="/d2fn/raw/8777d620caef32959713/perlin.js"></script>
	<script>

	var width = 960,
	height = 500,
	noiseScale = 0.003,
	actorStepLength = 1000,
	numActors = 10000,
	step = 0,
	steps = 150,
	gradientEpsilon = noiseScale / 100.0;

	var canvas = d3.select("body")
	.append("canvas")
	.attr({width: width, height: height});

	var context = canvas.node().getContext("2d");
	context.fillStyle = "rgb(0, 0, 0)";
	context.fillRect(-1, -1, width, height);

	var actors = [];
	for(var i = 0; i < numActors; i++) {
	actors.push(actor(width, height, noiseScale, actorStepLength));
	}

	var opacity = easeInOut(steps);

	d3.timer(function() {
	if(++step > steps) {
	console.log("done with animation");
	return true;
	}
	context.lineWidth = 1;
	context.globalCompositeOperation = 'lighter';
	context.beginPath();
	for(var i in actors) {
	var a = actors[i];
	var ln = a.step();
	var alpha = 0.6*opacity.get();
	context.strokeStyle = "rgba(49, 130, 189, " + alpha + ")";
	context.moveTo(ln.x1, ln.y1);
	context.lineTo(ln.x2, ln.y2);
	}
	context.stroke();
	opacity.step();
	});

	function actor(width, height, noiseScale, stepLength) {

	var x = Math.random() * width,
	y = Math.random() * height;

	var noise = perlin.noise(noiseScale);

	return {
	// get the last point and the next point
	step: function() {
	var x1 = x,
	y1 = y,
	grad = approximateGradient(noise, x, y, gradientEpsilon);
	x = x + stepLength * (-1 * grad.x),
	y = y + stepLength * (-1 * grad.y);
	return {
	x1: x1,
	y1: y1,
	x2: x,
	y2: y
	}
	}
	}
	}

	function easeInOut(steps) {
	var n = 0;
	var val = 0;
	return {
	step:
	function() {
	val = 0.075(1-Math.cos(2 Math.PI * (n++) / steps));
	},
	get:
	function() {
	return val;
	}
	};
	}

	function approximateGradient(f, x, y, h) {
	return {
	x: (f(x + h, y) - f(x - h, y)) / (2*h),
	y: (f(x, y + h) - f(x, y - h)) / (2*h)
	}
	}

	</script>