robinhouston/index.html

## index.html
<!DOCTYPE html>
<title>Triangular spiral</title>
<script src="http://bl.ocks.org/robinhouston/raw/6096562/rAF.js" charset="utf-8"></script>
<script src="http://bl.ocks.org/robinhouston/raw/6096562/doyle.js" charset="utf-8"></script>
<canvas width=960 height=500></canvas>
<script>
    // Initialisation
    var canvas = document.getElementsByTagName("canvas")[0],
        context = canvas.getContext("2d");


    // Complex arithmetic
    function cmul(w, z) {
        return [
            w[0]*z[0] - w[1]*z[1],
            w[0]*z[1] + w[1]*z[0]
        ];
    }
    function modulus(p) {
        return Math.sqrt(p[0]*p[0] + p[1]*p[1]);
    }
    function crecip(z) {
        var d = z[0]*z[0] + z[1]*z[1];
        return [z[0]/d, -z[1]/d];
    }


    // Doyle spiral drawing
    function spiral(r, start_point, delta, gamma, options) {
        var recip_delta = crecip(delta),
            mod_delta = modulus(delta),
            mod_recip_delta = 1/mod_delta,
            color_index = options.i,
            colors = options.fill,
            min_d = options.min_d,
            max_d = options.max_d;

        // Spiral inwards
        for (var q = start_point, mod_q = modulus(q);
            mod_q > min_d;
            q = cmul(q, recip_delta), mod_q *= mod_recip_delta
        ) {
            color_index = (color_index + colors.length - 1) % colors.length;
        }

        // Spiral outwards
        for (;mod_q < max_d; q = cmul(q, delta), mod_q *= mod_delta) {
            context.fillStyle = colors[color_index];

            context.beginPath();
            //context.arc(q[0], q[1], mod_q*r, 0, 7, false);
            context.moveTo.apply(context, q);
            context.lineTo.apply(context, cmul(q, delta));
            context.lineTo.apply(context, cmul(q, gamma));
            context.closePath();
            context.fill();

            color_index = (color_index + 1) % colors.length;
        }
    }


    // Animation
    var p = 9, q = 24;
    var root = doyle(p, q);

    var ms_per_repeat = 300;

    function frame(t) {
        context.setTransform(1, 0, 0, 1, 0, 0);
        context.clearRect(0, 0, canvas.width, canvas.height);

        context.translate(Math.round(canvas.width/2), cy = Math.round(canvas.height/2));
        var scale = Math.pow(root.mod_a, t);
        context.scale(scale, scale);
        context.rotate(root.arg_a * t);

        var min_d = 1/scale, max_d = canvas.width * 2;
        var start = root.a;
        for (var i=0; i<q; i++) {
            spiral(root.r, start, root.a, root.b, {
                fill: ["#483352"], i: 0, //, "#483352", "#486078"], i: (2*i)%3,
                min_d: min_d, max_d: max_d
            });
            start = cmul(start, root.b);
        }
    }

    var first_timestamp;
    function loop(timestamp) {
        if (!first_timestamp) first_timestamp = timestamp;
        frame(((timestamp - first_timestamp) % (ms_per_repeat*3)) / ms_per_repeat);
        requestAnimationFrame(loop);
    }

    requestAnimationFrame(loop);
</script>
	<!DOCTYPE html>
	<title>Triangular spiral</title>
	<script src="http://bl.ocks.org/robinhouston/raw/6096562/rAF.js" charset="utf-8"></script>
	<script src="http://bl.ocks.org/robinhouston/raw/6096562/doyle.js" charset="utf-8"></script>
	<canvas width=960 height=500></canvas>
	<script>
	// Initialisation
	var canvas = document.getElementsByTagName("canvas")[0],
	context = canvas.getContext("2d");


	// Complex arithmetic
	function cmul(w, z) {
	return [
	w[0]z[0] - w[1]z[1],
	w[0]z[1] + w[1]z[0]
	];
	}
	function modulus(p) {
	return Math.sqrt(p[0]p[0] + p[1]p[1]);
	}
	function crecip(z) {
	var d = z[0]z[0] + z[1]z[1];
	return [z[0]/d, -z[1]/d];
	}


	// Doyle spiral drawing
	function spiral(r, start_point, delta, gamma, options) {
	var recip_delta = crecip(delta),
	mod_delta = modulus(delta),
	mod_recip_delta = 1/mod_delta,
	color_index = options.i,
	colors = options.fill,
	min_d = options.min_d,
	max_d = options.max_d;

	// Spiral inwards
	for (var q = start_point, mod_q = modulus(q);
	mod_q > min_d;
	q = cmul(q, recip_delta), mod_q *= mod_recip_delta
	) {
	color_index = (color_index + colors.length - 1) % colors.length;
	}

	// Spiral outwards
	for (;mod_q < max_d; q = cmul(q, delta), mod_q *= mod_delta) {
	context.fillStyle = colors[color_index];

	context.beginPath();
	//context.arc(q[0], q[1], mod_q*r, 0, 7, false);
	context.moveTo.apply(context, q);
	context.lineTo.apply(context, cmul(q, delta));
	context.lineTo.apply(context, cmul(q, gamma));
	context.closePath();
	context.fill();

	color_index = (color_index + 1) % colors.length;
	}
	}


	// Animation
	var p = 9, q = 24;
	var root = doyle(p, q);

	var ms_per_repeat = 300;

	function frame(t) {
	context.setTransform(1, 0, 0, 1, 0, 0);
	context.clearRect(0, 0, canvas.width, canvas.height);

	context.translate(Math.round(canvas.width/2), cy = Math.round(canvas.height/2));
	var scale = Math.pow(root.mod_a, t);
	context.scale(scale, scale);
	context.rotate(root.arg_a * t);

	var min_d = 1/scale, max_d = canvas.width * 2;
	var start = root.a;
	for (var i=0; i<q; i++) {
	spiral(root.r, start, root.a, root.b, {
	fill: ["#483352"], i: 0, //, "#483352", "#486078"], i: (2*i)%3,
	min_d: min_d, max_d: max_d
	});
	start = cmul(start, root.b);
	}
	}

	var first_timestamp;
	function loop(timestamp) {
	if (!first_timestamp) first_timestamp = timestamp;
	frame(((timestamp - first_timestamp) % (ms_per_repeat*3)) / ms_per_repeat);
	requestAnimationFrame(loop);
	}

	requestAnimationFrame(loop);
	</script>