javascript - 如何在 d3 js 中的曲线上绘制 svg 圆圈？

Question

我正在编写一个软件，我在其中绘制了一些并排放置的 svg 圆圈，用户可以调整位置，更改线坐标。想要的结果是这样的

现在圆圈设置了一个不正确的空间，使圆圈向左移动

代码

function curve(val){
        var w = d3.select("#new_row_1").attr("width");

        var 
        numLines = 1,
        lineSpacing = 18,
        parabDepth = -30;

        var row_spacing = 18;

        if(val == 0){
            parabDepth = -18;
        }
        else if(val == 1){
            parabDepth = 0;
        }
        else if(val == 2){
            parabDepth = 20;
        }
        else if(val == 3){
            parabDepth = 30;
        }
        else if(val == 4){
            parabDepth = 40;
        }
        else if(val == 5){
            parabDepth = 50;
            // row_spacing = 18.41;
        }
        else if(val == 6){
            // row_spacing = 18.5;
            parabDepth = 60;
        }
        else if(val == 7){
            // row_spacing = 18.6;
            parabDepth = 70;
        }
        else if(val == 8){
            // row_spacing = 18.62;
            parabDepth = 80;
        }
        else if(val == 9){
            parabDepth = 90;
        }
        else if(val == 10){
            parabDepth = 100;
        }
        else if(val == 11){
            parabDepth = 110;
        }
        else if(val == 12){
            parabDepth = 120;
        }
        else if(val == 13){
            parabDepth = 130;
        }
        else if(val == 14){
            parabDepth = 140;
        }
        else if(val == 15){
            parabDepth = 150;
            row_spacing = 20;
        }

        width = w ;
        
        var curveData = [];

        curveData.push([0,0]);
        curveData.push([width/3 * 1, lineSpacing + parabDepth ]);
        curveData.push([width/3 * 2, lineSpacing + parabDepth ]);
        curveData.push([width/3 * 3, 1]);

        var line = d3.line()
            .x(function(d) {
              return d[0];
            })
            .y(function(d) {
              return d[1] + 8;
            })
            .curve(d3.curveCardinal);

        var svg = d3.select("#new_row_1").attr("height", (numLines * lineSpacing) + lineSpacing + parabDepth + row_spacing).attr("width", width);

        var g = svg.selectAll(".line")
            .data(d3.range(numLines))
            .enter()
            .append("g")
            .attr("class", "line")
            .attr("transform", function(d){
              return "translate(7," + (d*lineSpacing) + ")";
            });
        
        var path = g.append("path")
            .attr("d", line(curveData))
            .style("fill", "none")
            .style("stroke", "pink")
            .style("stroke-width","4")
            .each(function(){
                var g = d3.select(this.parentNode),
                    self = d3.select(this),
                    pathLength = width;
                  
                g.selectAll("circle")
                    .data(d3.range(1, width, row_spacing))
                    .enter()
                    .append("circle")
                    .attr("transform", (d,i) => {
                        var p = this.getPointAtLength(d);
                        return "translate(" + p.x + "," + p.y + ")";
                    })
                    .attr("r", 7)
                    .style("fill", function(d,i){
                        if(i == quant_col2 - 1){
                            return "red";
                        }else if(i == quant_col2/2){
                            return "yellow";
                        }
                        else if(i == quant_col2 - 2){
                            return "green";
                        }
                        else{
                            return "white";
                        }
                    })
                    .attr("stroke","black")
                    .attr("stroke-width","1");
            });
}

setTimeout(function(){
    curve(1)
},2000)

<script src="https://d3js.org/d3.v4.min.js"></script>

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<svg width="252" height="18" id="new_row_1" class="new_row" style="top: 150px; left: 302px; -webkit-tap-highlight-color: rgba(0, 0, 0, 0);"><g><circle cx="8" cy="8" r="7" style="fill: white; stroke: black; stroke-width: 1;"></circle><text dx="3" dy="11" class="label" style="font-size: 10px; font-weight: 500; display: none;">1</text></g><g><circle cx="26" cy="8" r="7" style="fill: white; stroke: black; stroke-width: 1;"></circle><text dx="21" dy="11" class="label" style="font-size: 10px; font-weight: 500; display: none;">2</text></g><g><circle cx="44" cy="8" r="7" style="fill: white; stroke: black; stroke-width: 1;"></circle><text dx="39" dy="11" class="label" style="font-size: 10px; font-weight: 500; display: none;">3</text></g><g><circle cx="62" cy="8" r="7" style="fill: white; stroke: black; stroke-width: 1;"></circle><text dx="57" dy="11" class="label" style="font-size: 10px; font-weight: 500; display: none;">4</text></g><g><circle cx="80" cy="8" r="7" style="fill: white; stroke: black; stroke-width: 1;"></circle><text dx="75" dy="11" class="label" style="font-size: 10px; font-weight: 500; display: none;">5</text></g><g><circle cx="98" cy="8" r="7" style="fill: white; stroke: black; stroke-width: 1;"></circle><text dx="93" dy="11" class="label" style="font-size: 10px; font-weight: 500; display: none;">6</text></g><g><circle cx="116" cy="8" r="7" style="fill: white; stroke: black; stroke-width: 1;"></circle><text dx="111" dy="11" class="label" style="font-size: 10px; font-weight: 500; display: none;">7</text></g><g><circle cx="134" cy="8" r="7" style="fill: white; stroke: black; stroke-width: 1;"></circle><text dx="129" dy="11" class="label" style="font-size: 10px; font-weight: 500; display: none;">8</text></g><g><circle cx="152" cy="8" r="7" style="fill: white; stroke: black; stroke-width: 1;"></circle><text dx="147" dy="11" class="label" style="font-size: 10px; font-weight: 500; display: none;">9</text></g><g><circle cx="170" cy="8" r="7" style="fill: white; stroke: black; stroke-width: 1;"></circle><text dx="165" dy="11" class="label" style="font-size: 10px; font-weight: 500; display: none;">10</text></g><g><circle cx="188" cy="8" r="7" style="fill: white; stroke: black; stroke-width: 1;"></circle><text dx="183" dy="11" class="label" style="font-size: 10px; font-weight: 500; display: none;">11</text></g><g><circle cx="206" cy="8" r="7" style="fill: white; stroke: black; stroke-width: 1;"></circle><text dx="201" dy="11" class="label" style="font-size: 10px; font-weight: 500; display: none;">12</text></g><g><circle cx="224" cy="8" r="7" style="fill: white; stroke: black; stroke-width: 1;"></circle><text dx="219" dy="11" class="label" style="font-size: 10px; font-weight: 500; display: none;">13</text></g><g><circle cx="242" cy="8" r="7" style="fill: white; stroke: black; stroke-width: 1;"></circle><text dx="237" dy="11" class="label" style="font-size: 10px; font-weight: 500; display: none;">14</text><g class="label" style="display: none;"><rect x="126" y="1" width="14" height="14" style="fill: black;"></rect><text dx="130" dy="11" style="font-size: 9px; font-weight: 400; fill: white;">A</text></g></g></svg>

该值将由用户控制，这意味着它会动态变化。我想通过生产线均匀地处理它们。怎么做到的？

Answer 1

您正在使用 getPointAtLength() 查找沿曲线一定距离处的点的 X、Y 坐标。显然这是错误的。您想找到给定 X 的 Y 坐标。

没有内置的 SVG 功能。你将不得不自己计算。为此，您需要贝塞尔方程的多项式形式，这并不简单。

由于您只制作抛物线，因此最好完全避免使用贝塞尔曲线，而只需使用普通的简单二次方程 (ax^2 + bx + c) 计算您的曲线.

另外:如果您决定坚持使用贝塞尔曲线，那么您真的应该使用二次贝塞尔曲线，而不是 cbic 曲线。二次贝塞尔曲线的特性是它们总是形成一条抛物线。