d3-force - 为什么这个图会脉动？

编程问答 2022-08-26

问题描述

下面的片段旨在模拟从 Web 服务中定期检索数据集（可能会更改）并将该数据合并到 d3 力导向图中。我将旧模拟节点对面的每个节点的位置和速度复制到新节点列表中，但是，每次重新启动模拟时，不紧靠 SVG 边界的节点都会略微向中心脉冲的图表。

如何避免这种影响？

function nodes() {
  let nodes = {};
  for (let ii = 0; ii <= 10; ii++) {
    nodes[`${ii}`] = {
      id: ii
    };
  }
  return nodes;
}

function links(nodes) {
  let links = {};
  for (var a in Object.keys(nodes)) {
    for (var b in Object.keys(nodes)) {
      links[`${nodes[a].id}-${nodes[b].id}`] = {
        id: `${nodes[a].id}-${nodes[b].id}`,source: `${nodes[a].id}`,target: `${nodes[b].id}`
      };
    }
  }
  return links;
}

let display = d3.selectAll("div");
var displaySize = display.node().getBoundingClientRect();
let r = 3;
let svg = display.append("svg");
let g = svg.append("g");

let node = g.selectAll("circle");
let link = g.selectAll("line");

function ticked() {
  node.attr("cx",d => d.x)
    .attr("cy",d => d.y);
  link.attr("x1",d => d.source.x)
    .attr("x2",d => d.target.x)
    .attr("y1",d => d.source.y)
    .attr("y2",d => d.target.y);
}

let simulation = d3.forceSimulation()
  .force("charge",d3.forceManyBody().strength(-100))
  .force("center",d3.forceCenter(displaySize.width / 2,displaySize.height / 2).strength(0.01))
  .force("link",d3.forceLink()
    .id(d => d.id)
    .distance(5).strength(0.01))
  .force("limit",d3.forceLimit()
    .x0(r).y0(r).x1(displaySize.width - r).y1(displaySize.height - r))
  .alphaMin(0.5)
  .on("tick",ticked)
  .on("end",update)
  .stop();

let localNodes = {};
let localLinks = {};

function update() {
  simulation.alpha(1).restart();
  let nextNodes = nodes();
  let nextLinks = links(nextNodes);
  for (var ii in nextNodes) {
    if (ii in localNodes) {
      nextNodes[ii].vx = localNodes[ii].vx;
      nextNodes[ii].vy = localNodes[ii].vy;
      nextNodes[ii].x = localNodes[ii].x;
      nextNodes[ii].y = localNodes[ii].y;
    }
  }
  for (var ii in nextLinks) {
    nextLinks[ii].target = nextNodes[nextLinks[ii].target];
    nextLinks[ii].source = nextNodes[nextLinks[ii].source];
  }
  
  localNodes = nextNodes;
  localLinks = nextLinks;

  node = g.selectAll("circle")
    .data(Object.values(localNodes),d => d.id)
    .join("circle")
    .attr("r",r);

  link = g.selectAll("line")
    .data(Object.values(localLinks),d => d.id)
    .join("line");

  simulation.nodes(Object.values(localNodes))
    .force("link").links(Object.values(localLinks));
}

update();
simulation.alpha(1).restart();
circle {
  stroke: #000;
  fill: #000;
}

line {
  stroke-width: 2px;
  stroke: #000;
}

div {
  position: relative;
  width: 100%;
  height: 90vh;
}

svg {
  position: absolute;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
}
<script src="https://d3js.org/d3.v6.js"></script>
<script src="https://unpkg.com/d3-force-limit@1.1.7/dist/d3-force-limit.min.js"></script>

<div></div>

解决方法

减少simulation.alpha() 值似乎减少了恒定脉冲。它仍然有运动，但比你原来的要少。这是你想要的吗？

function nodes() {
  let nodes = {};
  for (let ii = 0; ii <= 10; ii++) {
    nodes[`${ii}`] = {
      id: ii
    };
  }
  return nodes;
}

function links(nodes) {
  let links = {};
  for (var a in Object.keys(nodes)) {
    for (var b in Object.keys(nodes)) {
      links[`${nodes[a].id}-${nodes[b].id}`] = {
        id: `${nodes[a].id}-${nodes[b].id}`,source: `${nodes[a].id}`,target: `${nodes[b].id}`
      };
    }
  }
  return links;
}

let display = d3.selectAll("div");
var displaySize = display.node().getBoundingClientRect();
let r = 3;
let svg = display.append("svg");
let g = svg.append("g");

let node = g.selectAll("circle");
let link = g.selectAll("line");

function ticked() {
  node.attr("cx",d => d.x)
    .attr("cy",d => d.y);
  link.attr("x1",d => d.source.x)
    .attr("x2",d => d.target.x)
    .attr("y1",d => d.source.y)
    .attr("y2",d => d.target.y);
}

let simulation = d3.forceSimulation()
  .force("charge",d3.forceManyBody().strength(-100))
  .force("center",d3.forceCenter(displaySize.width / 2,displaySize.height / 2).strength(0.01))
  .force("link",d3.forceLink()
    .id(d => d.id)
    .distance(5).strength(0.01))
  .force("limit",d3.forceLimit()
    .x0(r).y0(r).x1(displaySize.width - r).y1(displaySize.height - r))
  .alphaMin(0.5)
  .on("tick",ticked)
  .on("end",update)
  .stop();

let localNodes = {};
let localLinks = {};

function update() {
  simulation.alpha(0.5).restart();
  let nextNodes = nodes();
  let nextLinks = links(nextNodes);
  for (var ii in nextNodes) {
    if (ii in localNodes) {
      nextNodes[ii].vx = localNodes[ii].vx;
      nextNodes[ii].vy = localNodes[ii].vy;
      nextNodes[ii].x = localNodes[ii].x;
      nextNodes[ii].y = localNodes[ii].y;
    }
  }
  for (var ii in nextLinks) {
    nextLinks[ii].target = nextNodes[nextLinks[ii].target];
    nextLinks[ii].source = nextNodes[nextLinks[ii].source];
  }
  
  localNodes = nextNodes;
  localLinks = nextLinks;

  node = g.selectAll("circle")
    .data(Object.values(localNodes),d => d.id)
    .join("circle")
    .attr("r",r);

  link = g.selectAll("line")
    .data(Object.values(localLinks),d => d.id)
    .join("line");

  simulation.nodes(Object.values(localNodes))
    .force("link").links(Object.values(localLinks));
    
}

update();
simulation.alpha(0.5).restart();
circle {
  stroke: #000;
  fill: #000;
}

line {
  stroke-width: 2px;
  stroke: #000;
}

div {
  position: relative;
  width: 100%;
  height: 90vh;
}

svg {
  position: absolute;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
}
<script src="https://d3js.org/d3.v6.js"></script>
<script src="https://unpkg.com/d3-force-limit@1.1.7/dist/d3-force-limit.min.js"></script>

<div></div>

减少更多会进一步减少图表的动能。您可以调整它，直到找到您喜欢的值。

function nodes() {
  let nodes = {};
  for (let ii = 0; ii <= 10; ii++) {
    nodes[`${ii}`] = {
      id: ii
    };
  }
  return nodes;
}

function links(nodes) {
  let links = {};
  for (var a in Object.keys(nodes)) {
    for (var b in Object.keys(nodes)) {
      links[`${nodes[a].id}-${nodes[b].id}`] = {
        id: `${nodes[a].id}-${nodes[b].id}`,update)
  .stop();

let localNodes = {};
let localLinks = {};

function update() {
  simulation.alpha(0.1).restart();
  let nextNodes = nodes();
  let nextLinks = links(nextNodes);
  for (var ii in nextNodes) {
    if (ii in localNodes) {
      nextNodes[ii].vx = localNodes[ii].vx;
      nextNodes[ii].vy = localNodes[ii].vy;
      nextNodes[ii].x = localNodes[ii].x;
      nextNodes[ii].y = localNodes[ii].y;
    }
  }
  for (var ii in nextLinks) {
    nextLinks[ii].target = nextNodes[nextLinks[ii].target];
    nextLinks[ii].source = nextNodes[nextLinks[ii].source];
  }
  
  localNodes = nextNodes;
  localLinks = nextLinks;

  node = g.selectAll("circle")
    .data(Object.values(localNodes),d => d.id)
    .join("line");

  simulation.nodes(Object.values(localNodes))
    .force("link").links(Object.values(localLinks));
    
}

update();
simulation.alpha(0.1).restart();
circle {
  stroke: #000;
  fill: #000;
}

line {
  stroke-width: 2px;
  stroke: #000;
}

div {
  position: relative;
  width: 100%;
  height: 90vh;
}

svg {
  position: absolute;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
}
<script src="https://d3js.org/d3.v6.js"></script>
<script src="https://unpkg.com/d3-force-limit@1.1.7/dist/d3-force-limit.min.js"></script>

<div></div>

d3-force-directedjavascript

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