SVG 无限动画无法正常工作

Question

我创建了 SVG 无限动画，但它运行不流畅，它卡在中间然后流出。在 SVG 的 Illustrator 中解决了节点，但之后我遇到了同样的问题。有人可以查看代码并帮助我吗？

.svg-main {
    width: 700px;
    margin: 30px auto;
    position: relative;
}
svg#svga {
    position: absolute;
    top: 0;
    left: auto;
    bottom: auto;
    right: auto;
}

.sd1{fill:none;stroke:#000000; stroke-width:6;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:10;}
.circ{fill:#000000; }
.st0{fill:#cccccc;}
.st1{fill:#cccccc;}
.st2{fill:none;stroke:#cccccc;stroke-width:6;stroke-miterlimit:10;}

<div class="svg-main">
<svg version="1.1" id="svga" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px"
  width="300px" height="200px" viewBox="0 0 685 310" style="enable-background:new 0 0 671.1 304.4;" xml:space="preserve"
 >
<g class="svg-col">
 <path class="sd1" id="loop-normal" d="M343.6,156.5c11,15.9,104.6,147.2,181.9,147.6c0.1,0,0.8,0,1,0c82.1-0.3,148.6-67,148.6-149.2
 c0-82.4-66.8-149.2-149.2-149.2c-77.2,0-170.8,131-182.2,147.5c-0.8,1.1-1.6,2.3-2.1,3.1c-10.6,15.3-104.8,147.8-182.4,147.8
 C76.7,304.2,9.9,237.4,9.9,155S76.7,5.8,159.1,5.8c77.2,0,170.7,130.9,182.2,147.5C342.1,154.4,342.9,155.6,343.6,156.5z"/>
  <animate attributeName="stroke-dasharray" attributeType="XML"
       from="1900, 1700"  to="200 1700"
       begin="0s" dur="3s"
       repeatCount="indefinite"/>
  <animate attributeName="stroke-dashoffset" attributeType="XML"
      from="-1700"  to="-3600"
      begin="0s" dur="3s"
      repeatCount="indefinite"/>  
 </path>

 <circle id="plug" class="circ" cx="0" cy="0" r="7"/> 
 <animateMotion
  xlink:href="#plug"
    dur="3s"
  rotate="auto"
  repeatCount="indefinite"
  calcMode="linear"
  keyTimes="0;1"    
  keySplines="0.42, 0, 0.58, 1">
  <mpath xlink:href="#loop-normal"/>
 </animateMotion> 
</g> 
</svg>
 
<!-- Generator: Adobe Illustrator 22.1.0, SVG Export Plug-In . SVG Version: 6.00 Build 0)  -->
<svg version="1.1" id="svg-bg" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px"
  width="300px" height="200px" viewBox="0 0 685 310" style="enable-background:new 0 0 685 310;" xml:space="preserve"> 
<path class="st2" d="M159.1,5.8C76.7,5.8,9.9,72.6,9.9,155s66.8,149.2,149.2,149.2S342.5,155,342.5,155S241.5,5.8,159.1,5.8z
  M525.9,5.8C443.5,5.8,342.5,155,342.5,155s101,149.2,183.4,149.2S675.1,237.4,675.1,155S608.3,5.8,525.9,5.8z"/>
</svg>
</div>

Answer 1

使用 stroke-dashoffset 动画获得流畅运动的第一个前提是知道适当精度的路径长度：

document.querySelector('#loop-normal').getTotalLength() // approx. 1910

省略stroke-dasharray的动画。而是将路径的总长度静态地分成一个破折号和一个间隙：stroke-dasharray="200 1710"。（任何其他比例都可以，只要总和等于 1910。）
您的 <animateMotion> 缺少 keyPoints 属性。将其设置为“0;1”
只要您不设置 calcMode="spline"，定义 keySplines 就没有任何效果。留着吧。

剩下的有点简化：只定义一次路径，并将背景和动画使用放在同一个 SVG 中；在 stroke-dashoffset 动画中命名正确的路径长度以确保平滑移动；删除未使用的 CSS.

.svg-main {
    width: 700px;
    margin: 30px auto;
    position: relative;
}
svg#svga {
    position: absolute;
    top: 0;
    left: auto;
    bottom: auto;
    right: auto;
}

.st2{fill:none;stroke:#cccccc;stroke-width:6;}
.sd1{fill:none;stroke:#000000; stroke-width:6;stroke-linecap:round;}
.circ{fill:#000000; }

<div class="svg-main">
<svg id="svga" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"
  width="300px" height="200px" viewBox="0 0 685 310">
  <g class="st2">
 <path id="loop-normal" d="M343.6,156.5c11,15.9,104.6,147.2,181.9,147.6c0.1,0,0.8,0,1,0c82.1-0.3,148.6-67,148.6-149.2
 c0-82.4-66.8-149.2-149.2-149.2c-77.2,0-170.8,131-182.2,147.5c-0.8,1.1-1.6,2.3-2.1,3.1c-10.6,15.3-104.8,147.8-182.4,147.8
 C76.7,304.2,9.9,237.4,9.9,155S76.7,5.8,159.1,5.8c77.2,0,170.7,130.9,182.2,147.5C342.1,154.4,342.9,155.6,343.6,156.5z"/>
  </g>
 <use class="sd1" stroke-dasharray="200 1710" xlink:href="#loop-normal">
  <animate attributeName="stroke-dashoffset"
      from="200"  to="-1710"
      begin="0s" dur="3s"
      repeatCount="indefinite"/>  
 </use>

 <circle id="plug" class="circ" cx="0" cy="0" r="7"/> 
 <animateMotion
  xlink:href="#plug"
    dur="3s"
  rotate="auto"
  repeatCount="indefinite"
  calcMode="linear"
  keyTimes="0;1"    
  keyPoints="0;1">
  <mpath xlink:href="#loop-normal"/>
 </animateMotion> 
</svg>
</div>

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