如何在 d3.js 中围绕中心旋转对象 [英] How to rotate an object around the center in d3.js

问题描述

我在 d3.js 中有两个简单的对象，它们应该围绕视口的中心旋转(就像行星围绕太阳).

I have two simple objects in d3.js, they should be circling around the center of the viewport (like planets around the sun).

我是 d3.js 的新手，我知道我必须使用过渡，但由于行星必须一直在旋转，而不仅仅是在进入或退出时，我不知道在哪里以及如何设置过渡.

I am new to d3.js and I know that I have to use transitions but as the planets have to circle all the time and not just on enter or exit I don't know where and how to set the transition.

这是我当前的代码:

var planets = [
    {d:100,r:2},
    {d:150,r:4}
];

var w = 500, h = 400, svg, circle;

function init(){

    svg = d3.select("#drawArea").append("svg").attr({width: w, height: h});

    var center = {
        x: Math.floor(w/2),
        y: Math.floor(h/2)
    };

    svg.append('circle').attr({
        'cx': center.x,
        'cy': center.y,
        'r': 10,
        'class': 'sun'
    });

    circle = svg.selectAll(".planet")
        .data(planets)
        .enter()
            .append("circle")
                .attr("class", "planet")
                .attr("r", function(s){return s.r});

    circle.attr({
        // distance from the center
        'cx': function(s){ return center.x - s.d; },
        // center of the screen
        'cy': function(s){ return center.y; }
    });

}

这里有一个 jsfiddle 可以玩.

And here is a jsfiddle to play around.

推荐答案

您需要:

1. 将您的行星放在以您的太阳为中心的 g 组中的 g 组
2. 创建一个 d3.timer，您可以在其中旋转团体.

对于 d3.timer 的使用示例，请参见 Mike Bostocks Epicyclic Gearing 示例.使用那个例子，我把类似于你问的东西放在一起:http://bl.ocks.org/4953593

For, example of the use of d3.timer see Mike Bostocks Epicyclic Gearing example. Using that example, I put together something similar to what you asked: http://bl.ocks.org/4953593

示例核心:

  var w = 800, h = 800;
  var t0 = Date.now();

  var planets = [
    { R: 300, r:  5, speed: 5, phi0: 90},
    { R: 150, r: 10, speed: 2, phi0: 190}
  ];


  var svg = d3.select("#planetarium").insert("svg")
    .attr("width", w).attr("height", h);

  svg.append("circle").attr("r", 20).attr("cx", w/2)
    .attr("cy", h/2).attr("class", "sun")

  var container = svg.append("g")
    .attr("transform", "translate(" + w/2 + "," + h/2 + ")")

  container.selectAll("g.planet").data(planets).enter().append("g")
    .attr("class", "planet").each(function(d, i) {
      d3.select(this).append("circle").attr("class", "orbit")
        .attr("r", d.R);
      d3.select(this).append("circle").attr("r", d.r).attr("cx",d.R)
        .attr("cy", 0).attr("class", "planet");
    });

  d3.timer(function() {
    var delta = (Date.now() - t0);
    svg.selectAll(".planet").attr("transform", function(d) {
      return "rotate(" + d.phi0 + delta * d.speed/200 + ")";
    });
  });

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