|
<!DOCTYPE html> |
|
<meta charset="utf-8"> |
|
<body> |
|
<script src="http://d3js.org/d3.v3.min.js"></script> |
|
<script> |
|
|
|
var points = [ |
|
[86, 388], |
|
[788, 40], |
|
[805, 447], |
|
[93, 72] |
|
]; |
|
|
|
var width = 960, |
|
height = 500; |
|
|
|
var color = d3.interpolateLab("#008000", "#c83a22"); |
|
|
|
var svg = d3.select("body").append("svg") |
|
.attr("width", width) |
|
.attr("height", height); |
|
|
|
var line = d3.svg.line() |
|
.interpolate("basis"); |
|
|
|
svg.selectAll("path") |
|
.data(quad(sample(line(points), 8))) |
|
.enter().append("path") |
|
.style("fill", function(d) { return color(d.t); }) |
|
.style("stroke", function(d) { return color(d.t); }) |
|
.attr("d", function(d) { return lineJoin(d[0], d[1], d[2], d[3], 32); }); |
|
|
|
// Sample the SVG path string "d" uniformly with the specified precision. |
|
function sample(d, precision) { |
|
var path = document.createElementNS(d3.ns.prefix.svg, "path"); |
|
path.setAttribute("d", d); |
|
|
|
var n = path.getTotalLength(), t = [0], i = 0, dt = precision; |
|
while ((i += dt) < n) t.push(i); |
|
t.push(n); |
|
|
|
return t.map(function(t) { |
|
var p = path.getPointAtLength(t), a = [p.x, p.y]; |
|
a.t = t / n; |
|
return a; |
|
}); |
|
} |
|
|
|
// Compute quads of adjacent points [p0, p1, p2, p3]. |
|
function quad(points) { |
|
return d3.range(points.length - 1).map(function(i) { |
|
var a = [points[i - 1], points[i], points[i + 1], points[i + 2]]; |
|
a.t = (points[i].t + points[i + 1].t) / 2; |
|
return a; |
|
}); |
|
} |
|
|
|
// 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> |
