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Custom Animation

animation5 vector80 feature12 flash1

Demonstrates how to animate features.

This example shows how to use postrender and vectorContext to animate features. Here we choose to do a flash animation each time a feature is added to the layer.

main.js
import Feature from 'ol/Feature.js';
import Map from 'ol/Map.js';
import Point from 'ol/geom/Point.js';
import View from 'ol/View.js';
import {Circle as CircleStyle, Stroke, Style} from 'ol/style.js';
import {OSM, Vector as VectorSource} from 'ol/source.js';
import {Tile as TileLayer, Vector as VectorLayer} from 'ol/layer.js';
import {easeOut} from 'ol/easing.js';
import {fromLonLat} from 'ol/proj.js';
import {getVectorContext} from 'ol/render.js';
import {unByKey} from 'ol/Observable.js';

const tileLayer = new TileLayer({
  source: new OSM({
    wrapX: false,
  }),
});

const source = new VectorSource({
  wrapX: false,
});
const vector = new VectorLayer({
  source: source,
});

const map = new Map({
  layers: [tileLayer, vector],
  target: 'map',
  view: new View({
    center: [0, 0],
    zoom: 1,
    multiWorld: true,
  }),
});

function addRandomFeature() {
  const x = Math.random() * 360 - 180;
  const y = Math.random() * 170 - 85;
  const geom = new Point(fromLonLat([x, y]));
  const feature = new Feature(geom);
  source.addFeature(feature);
}

const duration = 3000;
function flash(feature) {
  const start = Date.now();
  const flashGeom = feature.getGeometry().clone();
  const listenerKey = tileLayer.on('postrender', animate);

  function animate(event) {
    const frameState = event.frameState;
    const elapsed = frameState.time - start;
    if (elapsed >= duration) {
      unByKey(listenerKey);
      return;
    }
    const vectorContext = getVectorContext(event);
    const elapsedRatio = elapsed / duration;
    // radius will be 5 at start and 30 at end.
    const radius = easeOut(elapsedRatio) * 25 + 5;
    const opacity = easeOut(1 - elapsedRatio);

    const style = new Style({
      image: new CircleStyle({
        radius: radius,
        stroke: new Stroke({
          color: 'rgba(255, 0, 0, ' + opacity + ')',
          width: 0.25 + opacity,
        }),
      }),
    });

    vectorContext.setStyle(style);
    vectorContext.drawGeometry(flashGeom);
    // tell OpenLayers to continue postrender animation
    map.render();
  }
}

source.on('addfeature', function (e) {
  flash(e.feature);
});

window.setInterval(addRandomFeature, 1000);
index.html
<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>Custom Animation</title>
    <link rel="stylesheet" href="node_modules/ol/ol.css">
    <style>
      .map {
        width: 100%;
        height: 400px;
      }
    </style>
  </head>
  <body>
    <div id="map" class="map"></div>

    <script type="module" src="main.js"></script>
  </body>
</html>
package.json
{
  "name": "feature-animation",
  "dependencies": {
    "ol": "10.3.1"
  },
  "devDependencies": {
    "vite": "^3.2.3"
  },
  "scripts": {
    "start": "vite",
    "build": "vite build"
  }
}