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我画了直接图，所以我画了箭头到直线上，我是 pixi.js 和 javascript 的新手，我想学习它，你能帮我画一个箭头吗？

这是一个演示，我想在链接中添加箭头。

这是在这个类中绘制链接的代码

module.exports = function (link, ctx) {
  ctx.lineStyle(link.width, 0x333333, 1);
  ctx.moveTo(link.from.x, link.from.y);
  ctx.lineTo(link.to.x, link.to.y);
}

这是完整的代码

module.exports.main = function () {
  var graph = require('ngraph.generators').balancedBinTree(5);
  var createPixiGraphics = require('../');

  var setting = {
    rendererOptions: {
      backgroundColor: 0xFFFFFF,
      antialias: true,
    }
  }

  var pixiGraphics = createPixiGraphics(graph, setting);
  pixiGraphics.createLinkUI(require('./lib/createLinkUI'));
  pixiGraphics.renderLink(require('./lib/renderLink'));
  pixiGraphics.createNodeUI(require('./lib/createNodeUI'));
  pixiGraphics.renderNode(require('./lib/renderNode'));
  var layout = pixiGraphics.layout;

  // just make sure first node does not move:
  layout.pinNode(graph.getNode(1), true);

  // begin animation loop:
  pixiGraphics.run();
}

重现代码的链接在这里

非常感谢

4

1 回答 1

5

据我所知，pixi.js 不支持开箱即用的箭头渲染。您必须手动绘制箭头。这个想法是使用原始向量运算来计算箭头的翅膀应该在哪里。

如果您使用归一化向量（长度等于 1 的向量）进行操作，则更容易实现。一旦你有了一个图形链接的向量，你就知道它的方向，然后你可以计算链接上的偏移量，箭头翅膀应该停止的地方。一旦你有了偏移，你所要做的就是取一个正交向量并从你的原始向量向左/向右步进——这些是你的箭头翅膀应该停止的点。

如果你画一张图会更容易理解，但我目前没有好的钢笔和铅笔，所以这里是呈现箭头的代码：

function defaultLinkRenderer(link) {
  graphics.lineStyle(1, 0xcccccc, 1);
  graphics.moveTo(link.from.x, link.from.y);
  graphics.lineTo(link.to.x, link.to.y);

  // first, let's compute normalized vector for our link:
  let dx = link.to.x - link.from.x;
  let dy = link.to.y - link.from.y;
  let l = Math.sqrt(dx * dx + dy * dy);

  if (l === 0) return; // if length is 0 - can't render arrows

  // This is our normal vector. It describes direction of the graph
  // link, and has length == 1:
  let nx = dx/l; let ny = dy/l;

  // Now let's draw the arrow:
  let arrowLength = 6;       // Length of the arrow
  let arrowWingsLength = 2;  // How far arrow wings are from the link?

  // This is where arrow should end. We do `(l - NODE_WIDTH)` to
  // make sure it ends before the node UI element.
  let ex = link.from.x + nx * (l - NODE_WIDTH);
  let ey = link.from.y + ny * (l - NODE_WIDTH);

  // Offset on the graph link, where arrow wings should be
  let sx = link.from.x + nx * (l - NODE_WIDTH - arrowLength);
  let sy = link.from.y + ny * (l - NODE_WIDTH - arrowLength);

  // orthogonal vector to the link vector is easy to compute:
  let topX = -ny;
  let topY = nx;

  // Let's draw the arrow:
  graphics.moveTo(ex, ey);
  graphics.lineTo(sx + topX * arrowWingsLength, sy + topY * arrowWingsLength);
  graphics.moveTo(ex, ey);
  graphics.lineTo(sx - topX * arrowWingsLength, sy - topY * arrowWingsLength);
}

这会呈现出漂亮的箭头：

最后结果

于 2019-10-26T19:07:10.327 回答