A recreation of an earlier Protovis example, reminiscent of peristalsis.
<!DOCTYPE html>
<meta charset="utf-8">
<style>
body {
background: #333;
}
</style>
<body>
<script src="//d3js.org/d3.v3.min.js"></script>
<script>
var margin = {top: 100, right: 100, bottom: 100, left: 100},
width = 960 - margin.left - margin.right,
height = 500 - margin.top - margin.bottom;
var x = d3.scale.linear()
.domain([0, 5.9])
.range([0, width]);
var y = d3.scale.linear()
.domain([-1, 1])
.range([height, 0]);
var z = d3.scale.linear()
.domain([0, 5.9])
.range([0, 360]);
var points = d3.range(0, 6, .1).map(function(t) {
return {value: t, 0: x(t), 1: y(Math.sin(t))};
});
var svg = d3.select("body").append("svg")
.attr("width", width + margin.left + margin.right)
.attr("height", height + margin.top + margin.bottom)
.append("g")
.attr("transform", "translate(" + margin.left + "," + margin.top + ")");
var path = svg.selectAll("path")
.data(quad(points))
.enter().append("path")
.style("fill", function(d) { return d3.hsl(z(d[1].value), 1, .5); })
.style("stroke", "#000");
var t0 = Date.now();
d3.timer(function() {
var dt = (Date.now() - t0) * .001;
points.forEach(function(d) { d[1] = y(d.scale = Math.sin(d.value + dt)); });
path.attr("d", function(d) { return lineJoin(d[0], d[1], d[2], d[3], 80 * d[1].scale * d[1].scale + 10); });
});
// Compute quads of adjacent points [p0, p1, p2, p3].
function quad(points) {
return d3.range(points.length - 1).map(function(i) {
return [points[i - 1], points[i], points[i + 1], points[i + 2]];
});
}
// Compute stroke outline for segment p12.
function lineJoin(p0, p1, p2, p3, width) {
var u12 = perp(p1, p2),
r = width / 2,
a = [p1[0] + u12[0] * r, p1[1] + u12[1] * r],
b = [p2[0] + u12[0] * r, p2[1] + u12[1] * r],
c = [p2[0] - u12[0] * r, p2[1] - u12[1] * r],
d = [p1[0] - u12[0] * r, p1[1] - u12[1] * r];
if (p0) { // clip ad and dc using average of u01 and u12
var u01 = perp(p0, p1), e = [p1[0] + u01[0] + u12[0], p1[1] + u01[1] + u12[1]];
a = lineIntersect(p1, e, a, b);
d = lineIntersect(p1, e, d, c);
}
if (p3) { // clip ab and dc using average of u12 and u23
var u23 = perp(p2, p3), e = [p2[0] + u23[0] + u12[0], p2[1] + u23[1] + u12[1]];
b = lineIntersect(p2, e, a, b);
c = lineIntersect(p2, e, d, c);
}
return "M" + a + "L" + b + " " + c + " " + d + "Z";
}
// Compute intersection of two infinite lines ab and cd.
function lineIntersect(a, b, c, d) {
var x1 = c[0], x3 = a[0], x21 = d[0] - x1, x43 = b[0] - x3,
y1 = c[1], y3 = a[1], y21 = d[1] - y1, y43 = b[1] - y3,
ua = (x43 * (y1 - y3) - y43 * (x1 - x3)) / (y43 * x21 - x43 * y21);
return [x1 + ua * x21, y1 + ua * y21];
}
// Compute unit vector perpendicular to p01.
function perp(p0, p1) {
var u01x = p0[1] - p1[1], u01y = p1[0] - p0[0],
u01d = Math.sqrt(u01x * u01x + u01y * u01y);
return [u01x / u01d, u01y / u01d];
}
</script>