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WebGL Vector Layer

vector79 geojson9 webgl17

 

Example of a vector layer rendered using WebGL

The ecoregions are loaded from a GeoJSON file.

main.js
import GeoJSON from 'ol/format/GeoJSON.js';
import Layer from 'ol/layer/Layer.js';
import Map from 'ol/Map.js';
import OSM from 'ol/source/OSM.js';
import TileLayer from 'ol/layer/WebGLTile.js';
import VectorSource from 'ol/source/Vector.js';
import View from 'ol/View.js';
import WebGLVectorLayerRenderer from 'ol/renderer/webgl/VectorLayer.js';

/** @type {import('ol/style/webgl.js').WebGLStyle} */
const style = {
  'stroke-color': ['*', ['get', 'COLOR'], [220, 220, 220]],
  'stroke-width': 2,
  'stroke-offset': -1,
  'fill-color': ['*', ['get', 'COLOR'], [255, 255, 255, 0.6]],
};

class WebGLLayer extends Layer {
  createRenderer() {
    return new WebGLVectorLayerRenderer(this, {
      style,
    });
  }
}

const osm = new TileLayer({
  source: new OSM(),
});

const vectorLayer = new WebGLLayer({
  source: new VectorSource({
    url: 'https://openlayers.org/data/vector/ecoregions.json',
    format: new GeoJSON(),
  }),
});

const map = new Map({
  layers: [osm, vectorLayer],
  target: 'map',
  view: new View({
    center: [0, 0],
    zoom: 1,
  }),
});

const featureOverlay = new WebGLLayer({
  source: new VectorSource(),
  map: map,
  style: {
    'stroke-color': 'rgba(255, 255, 255, 0.7)',
    'stroke-width': 1,
  },
});

let highlight;
const displayFeatureInfo = function (pixel) {
  const feature = map.forEachFeatureAtPixel(pixel, function (feature) {
    return feature;
  });

  const info = document.getElementById('info');
  if (feature) {
    info.innerHTML = feature.get('ECO_NAME') || ' ';
  } else {
    info.innerHTML = ' ';
  }

  if (feature !== highlight) {
    if (highlight) {
      featureOverlay.getSource().removeFeature(highlight);
    }
    if (feature) {
      featureOverlay.getSource().addFeature(feature);
    }
    highlight = feature;
  }
};

map.on('pointermove', function (evt) {
  if (evt.dragging) {
    return;
  }
  const pixel = map.getEventPixel(evt.originalEvent);
  displayFeatureInfo(pixel);
});

map.on('click', function (evt) {
  displayFeatureInfo(evt.pixel);
});
index.html
<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>WebGL Vector Layer</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>
    <div id="info">&nbsp;</div>

    <script type="module" src="main.js"></script>
  </body>
</html>
package.json
{
  "name": "webgl-vector-layer",
  "dependencies": {
    "ol": "9.2.2"
  },
  "devDependencies": {
    "vite": "^3.2.3"
  },
  "scripts": {
    "start": "vite",
    "build": "vite build"
  }
}