更改D3方向力图中箭头标记的方向

您应该查看标记的"orient"属性：https://www.w3.org/TR/svg-markers/#OrientAttribute

在您的情况下，类似于.attr("orient", "auto-start-reverse")或.attr("orient", 180)的内容会起作用。

在这篇文章中可以找到一个例子：在D3力量布局链接中间显示一个箭头

至于曲率，相关部分为

dr = Math.sqrt(dx * dx + dy * dy);

半径dr越大，曲线就越多。

svg.select("defs").append("marker")
    .attr("id", "start")
    .attr("viewBox", "0 -5 10 10")
    .attr("refX", -5)
    .attr("refY", 0)
    .attr("markerWidth", 6)
    .attr("markerHeight", 6)    
    .attr("orient", "auto")
    .append("path")
    .attr("d", "M0,0L10,-5L10,5");
var path = svg.append("svg:g").selectAll("path")
    .data(force.links())
    .enter().append("svg:path")
    .attr("class", "link")
    .attr("marker-start", "url(#start)")
    .attr("marker-end", "url(#end)");

var links= [
  {
    "source": "Harry",
    "target": "Sally",
    "value": 1.2
  },
  {
    "source": "Harry",
    "target": "Mario",
    "value": 1.3
  },
  {
    "source": "Sarah",
    "target": "Alice",
    "value": 0.2
  },
  {
    "source": "Eveie",
    "target": "Alice",
    "value": 0.5
  },
  {
    "source": "Peter",
    "target": "Alice",
    "value": 1.6
  },
  {
    "source": "Mario",
    "target": "Alice",
    "value": 0.4
  },
  {
    "source": "James",
    "target": "Alice",
    "value": 0.6
  },
  {
    "source": "Harry",
    "target": "Carol",
    "value": 0.7
  },
  {
    "source": "Harry",
    "target": "Nicky",
    "value": 0.8
  },
  {
    "source": "Bobby",
    "target": "Frank",
    "value": 0.8
  },
  {
    "source": "Alice",
    "target": "Mario",
    "value": 0.7
  },
  {
    "source": "Harry",
    "target": "Lynne",
    "value": 0.5
  },
  {
    "source": "Sarah",
    "target": "James",
    "value": 1.9
  },
  {
    "source": "Roger",
    "target": "James",
    "value": 1.1
  },
  {
    "source": "Maddy",
    "target": "James",
    "value": 0.3
  },
  {
    "source": "Sonny",
    "target": "Roger",
    "value": 0.5
  },
  {
    "source": "James",
    "target": "Roger",
    "value": 1.5
  },
  {
    "source": "Alice",
    "target": "Peter",
    "value": 1.1
  },
  {
    "source": "Johan",
    "target": "Peter",
    "value": 1.6
  },
  {
    "source": "Alice",
    "target": "Eveie",
    "value": 0.5
  },
  {
    "source": "Harry",
    "target": "Eveie",
    "value": 0.1
  }
];
var nodes = {};
// Compute the distinct nodes from the links.
links.forEach(function(link) {
    link.source = nodes[link.source] || 
        (nodes[link.source] = {name: link.source});
    link.target = nodes[link.target] || 
        (nodes[link.target] = {name: link.target});
    link.value = +link.value;
});
var width = 960,
    height = 500;
var force = d3.layout.force()
    .nodes(d3.values(nodes))
    .links(links)
    .size([width, height])
    .linkDistance(60)
    .charge(-300)
    .on("tick", tick)
    .start();
var svg = d3.select("body").append("svg")
    .attr("width", width)
    .attr("height", height);
// build the arrow.
svg.append("svg:defs").selectAll("marker")
    .data(["end"])      // Different link/path types can be defined here
  .enter().append("svg:marker")    // This section adds in the arrows
    .attr("id", String)
    .attr("viewBox", "0 -5 10 10")
    .attr("refX", 15)
    .attr("refY", -1.5)
    .attr("markerWidth", 6)
    .attr("markerHeight", 6)
    .attr("orient", "auto")
  .append("svg:path")
    .attr("d", "M0,-5L10,0L0,5");
svg.select("defs").append("marker")
    .attr("id", "start")
    .attr("viewBox", "0 -5 10 10")
    .attr("refX", -5)
    .attr("refY", 0)
    .attr("markerWidth", 6)
    .attr("markerHeight", 6)    
    .attr("orient", "auto")
    .append("path")
    .attr("d", "M0,0L10,-5L10,5");
// add the links and the arrows
var path = svg.append("svg:g").selectAll("path")
    .data(force.links())
    .enter().append("svg:path")
    .attr("class", "link")
    .attr("marker-start", "url(#start)")
    .attr("marker-end", "url(#end)");
// define the nodes
var node = svg.selectAll(".node")
    .data(force.nodes())
  .enter().append("g")
    .attr("class", "node")
    .call(force.drag);
// add the nodes
node.append("circle")
    .attr("r", 5);
// add the text 
node.append("text")
    .attr("x", 12)
    .attr("dy", ".35em")
    .text(function(d) { return d.name; });
// add the curvy lines
function tick() {
    path.attr("d", function(d) {
        var dx = d.target.x - d.source.x,
            dy = d.target.y - d.source.y,
            dr = Math.sqrt(dx * dx + dy * dy);
        return "M" + 
            d.source.x + "," + 
            d.source.y + "A" + 
            dr + "," + dr + " 0 0,1 " + 
            d.target.x + "," + 
            d.target.y;
    });
    node
        .attr("transform", function(d) { 
  	    return "translate(" + d.x + "," + d.y + ")"; });
}

path.link {
  fill: none;
  stroke: #666;
  stroke-width: 1.5px;
}
circle {
  fill: #ccc;
  stroke: #fff;
  stroke-width: 1.5px;
}
text {
  fill: #000;
  font: 10px sans-serif;
  pointer-events: none;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.4.11/d3.min.js"></script>