ParticleLayer: an example
index.html
<!DOCTYPE html>
<html>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Layer - ParticleLayer: an example</title>
  <style type="text/css">
    html,body{margin:0px;height:100%;width:100%}
    .container{width:100%;height:100%}
  </style>
  <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/[email protected]/dist/maptalks.css">
  <script type="text/javascript" src="https://cdn.jsdelivr.net/npm/[email protected]/dist/maptalks.min.js"></script>
  <body>
    <div id="map" class="container"></div>

    <script>
      var map = new maptalks.Map('map', {
        center: [-0.113049,51.498568],
        zoom: 14,
        baseLayer: new maptalks.TileLayer('base', {
          urlTemplate: 'http://{s}.basemaps.cartocdn.com/light_all/{z}/{x}/{y}.png',
          subdomains: ['a','b','c','d'],
          attribution: '&copy; <a href="http://osm.org">OpenStreetMap</a> contributors, &copy; <a href="https://carto.com/">CARTO</a>'
        }),
        layers : [
          new maptalks.VectorLayer('v')
        ]
      });

      // An animated particle circle
      var particles = new maptalks.ParticleLayer('c', {
        'forceRenderOnMoving' : true
      });

      var center = map.getCenter();
      // circle's radius in meters
      var radius = 1000;

      particles.getParticles = function (t) {
        var point = map.coordinateToContainerPoint(center);
        // particle's angle at current time
        var angle = (t / 16 % 360) * Math.PI / 180;
        // convert distance in meter to pixel length
        var pxLen = map.distanceToPixel(radius, radius);
        var r = pxLen.width;
        // caculate pixel offset from circle's center
        var x = r * Math.cos(angle),
          y = r * Math.sin(angle);
        return [
          {
            point : point.add(x, y),
            r : 4,
            color : 'rgb(135,196,240)'
          }
        ];
      };

      map.addLayer(particles);

      new maptalks.Marker(center, {
        symbol : {
          markerType : 'cross',
          markerWidth : 10,
          markerHeight : 10,
          markerLineWidth : 2
        }
      })
      .addTo(map.getLayer('v'));

      new maptalks.Circle(center, 1000, {
        symbol : {
          lineColor : '#fff',
          lineWidth : 6,
          lineOpacity : 0.2,
          polygonOpacity : 0
        }
      })
      .addTo(map.getLayer('v'));

    </script>
  </body>
</html>
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