之前用d3做了多条线之间的绘图是曲线表示的，现在产品要求改成平行线的样式，经过在网上的调研和自己的尝试，实践出一个可用的方法，分享给大家，先展示下结果：
事先声明，本方法是在以下参考网站上进行的结合和更改：
d3力导图节点间多条线的绘图方法
d3.js Force Layout: drawing multiple straight, parallel links between two nodes
force layout with multiple links between nodes
如果图示的样式是你想要的，那么直接粘贴代码看吧！代码可直接运行。
<!DOCTYPE html>
<head>
<meta charset="utf-8">
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/3.5.0/lodash.min.js"></script>
<script src="https://d3js.org/d3.v3.min.js"></script>
<style>
body {
margin: 0;
position: fixed;
top: 0;
right: 0;
bottom: 0;
left: 0;
}
path {
fill: none;
stroke-width: 3;
}
circle {
stroke: white;
stroke-width: 2;
}
</style>
</head>
<body>
<script>
// DATA
var nodes = [{}, {}];
var links = [
// links 可更改，自己改数量显示不同的条数
{ source: 0, target: 1 },
{ source: 0, target: 1 },
{ source: 0, target: 1 },
{ source: 0, target: 1 },
{ source: 0, target: 1 }
];
_.each(links, function (link) {
var same = _.filter(links, {
source: link.source,
target: link.target
});
var sameAlt = _.filter(links, {
source: link.target,
target: link.source
});
var sameAll = same.concat(sameAlt);
_.each(sameAll, function (s, i) {
s.sameIndex = i + 1;
s.sameTotal = sameAll.length;
s.sameTotalHalf = s.sameTotal / 2;
s.sameUneven = s.sameTotal % 2 !== 0;
s.sameMiddleLink =
s.sameUneven === true && Math.ceil(s.sameTotalHalf) === s.sameIndex;
s.sameLowerHalf = s.sameIndex <= s.sameTotalHalf;
s.sameArcDirection = s.sameLowerHalf ? 0 : 1;
s.sameIndexCorrected = s.sameLowerHalf
? s.sameIndex
: s.sameIndex - Math.ceil(s.sameTotalHalf);
});
});
var maxSame = _.chain(links)
.sortBy(function (x) {
return x.sameTotal;
})
.last()
.value().sameTotal;
_.each(links, function (link) {
link.maxSameHalf = Math.floor(maxSame / 3);
});
// FORCE
var width = 960,
height = 500;
var force = d3.layout.force()
.nodes(nodes)
.links(links)
.size([width, height])
.linkDistance(400)
.charge(-2000)
.on('tick', tick)
.start();
var svg = d3.select("body").append("svg")
.attr("width", width)
.attr("height", height);
var path = svg.append("g").selectAll("path")
.data(force.links())
.enter().append("path")
.style("stroke", function (d) {
return d3.scale.category20().range()[d.sameIndex - 1];
});
var circle = svg.append("g").selectAll("circle")
.data(force.nodes())
.enter().append("circle")
.attr("r", 30)
.call(force.drag);
// TICK
function tick(d) {
circle.attr("transform", function (d) {
return "translate(" + d.x + "," + d.y + ")";
});
path.attr("d", linkArc);
}
function calcTranslationExact(targetDistance, source, target) {
var x1_x0 = target.x - source.x,
y1_y0 = target.y - source.y,
x2_x0, y2_y0;
if (y1_y0 === 0) {
x2_x0 = 0;
y2_y0 = targetDistance;
} else {
let angle = Math.atan((x1_x0) / (y1_y0));
x2_x0 = -targetDistance * Math.cos(angle);
y2_y0 = targetDistance * Math.sin(angle);
}
return {
dx: x2_x0,
dy: y2_y0
};
}
// some more info: http://stackoverflow.com/questions/11368339/drawing-multiple-edges-between-two-nodes-with-d3
function linkArc(d) {
var dx = (d.target.x - d.source.x),
dy = (d.target.y - d.source.y),
dr = Math.sqrt(dx * dx + dy * dy),
arc = 0;
// 上下不一样的间隔
let dis1 = calcTranslationExact(d.sameIndex * 12, d.source, d.target)
let dis2 = calcTranslationExact(-(d.sameIndex - Math.ceil(d.sameTotalHalf)) * 12, d.source, d.target)
let dx1 = dis1.dx;
let dy1 = dis1.dy
let dx2 = dis2.dx;
let dy2 = dis2.dy
// 表示奇数的时候，中间的那条
if (Math.ceil(d.sameTotalHalf) === d.sameIndex && d.sameUneven === true) {
dx1 = 0;
dx2 = 0;
dy1 = 0;
dy2 = 0;
}
if (d.sameArcDirection === 0) {
return "M" + (d.source.x + dx1) + "," + (d.source.y + dy1) + "A" + arc + "," + arc + " 0 0," + 0 + " " + (d.target.x + dx1) + "," + (d.target.y + dy1);
} else {
return "M" + (d.source.x + dx2) + "," + (d.source.y + dy2) + "A" + arc + "," + arc + " 0 0," + 0 + " " + (d.target.x + dx2) + "," + (d.target.y + dy2);
}
}
</script>
</body>