Illustrates the use of mask layers.

Mask layer
100% © Mapbox

A MaskLayer can be used to mask part of a map. By default, the transparent part of the mask makes the map transparent. By inverting the mask, the transparent part of the mask makes the map opaque.

index.js
import XYZ from 'ol/source/XYZ.js';
import { Fill, Stroke, Style } from 'ol/style.js';
import { GeoJSON } from 'ol/format.js';

import { MapControls } from 'three/examples/jsm/controls/MapControls.js';

import Extent from '@giro3d/giro3d/core/geographic/Extent.js';
import Instance from '@giro3d/giro3d/core/Instance.js';
import TiledImageSource from '@giro3d/giro3d/sources/TiledImageSource.js';
import ColorLayer from '@giro3d/giro3d/core/layer/ColorLayer.js';
import Map from '@giro3d/giro3d/entities/Map.js';
import Inspector from '@giro3d/giro3d/gui/Inspector.js';
import MaskLayer, { MaskMode } from '@giro3d/giro3d/core/layer/MaskLayer.js';
import VectorSource from '@giro3d/giro3d/sources/VectorSource.js';

// Defines geographic extent: CRS, min/max X, min/max Y
const extent = Extent.fromCenterAndSize('EPSG:3857', { x: 260000, y: 6251379 }, 32000, 32000);

// `viewerDiv` will contain Giro3D' rendering area (the canvas element)
const viewerDiv = document.getElementById('viewerDiv');

// Creates a Giro3D instance
const instance = new Instance(viewerDiv, {
    crs: extent.crs(),
    renderer: {
        clearColor: false,
    },
});

const apiKey =
    'pk.eyJ1IjoidG11Z3VldCIsImEiOiJjbGJ4dTNkOW0wYWx4M25ybWZ5YnpicHV6In0.KhDJ7W5N3d1z3ArrsDjX_A';

// Adds the map that will contain the layers.
const map = new Map('Paris', { extent });

instance.add(map);

// Adds a satellite basemap
const basemap = new ColorLayer({
    name: 'basemap',
    extent,
    source: new TiledImageSource({
        source: new XYZ({
            url: `https://api.mapbox.com/v4/mapbox.satellite/{z}/{x}/{y}.webp?access_token=${apiKey}`,
            projection: extent.crs(),
            crossOrigin: 'anonymous',
        }),
    }),
});
map.addLayer(basemap);

const outlineStyle = new Style({
    stroke: new Stroke({ color: 'red', width: 2 }),
});

// Display the footprint using a red outline. This layer is not necessary for the mask to work,
// and is only present for illustration purposes.
const outline = new ColorLayer({
    name: 'outline',
    source: new VectorSource({
        format: new GeoJSON(),
        data: 'https://3d.oslandia.com/giro3d/vectors/paris.geojson',
        style: outlineStyle,
    }),
});

map.addLayer(outline);

// The mask layer uses an opaque fill style.
const maskStyle = new Style({
    fill: new Fill({ color: 'white' }),
});

// Create the actual mask layer with the same source as the outline.
const mask = new MaskLayer({
    name: 'mask',
    source: new VectorSource({
        format: new GeoJSON(),
        data: 'https://3d.oslandia.com/giro3d/vectors/paris.geojson',
        style: maskStyle,
    }),
});

map.addLayer(mask);

// Sets the camera position
const center = extent.centerAsVector3();
instance.camera.camera3D.position.set(center.x, center.y - 1, 40000);

// Creates controls
const controls = new MapControls(instance.camera.camera3D, viewerDiv);

// Then looks at extent's center
controls.target = center;
controls.saveState();

controls.enableDamping = true;
controls.dampingFactor = 0.2;
controls.maxPolarAngle = Math.PI / 2.3;

instance.useTHREEControls(controls);

Inspector.attach(document.getElementById('panelDiv'), instance);

// Bind events

document.getElementById('layerState').addEventListener('change', e => {
    const newMode = parseInt(e.target.value, 10);

    switch (newMode) {
        case 1:
            mask.visible = true;
            mask.maskMode = MaskMode.Normal;
            break;
        case 2:
            mask.visible = true;
            mask.maskMode = MaskMode.Inverted;
            break;
        default:
            mask.visible = false;
            break;
    }

    instance.notifyChange(map);
});
index.html
<!doctype html>
<html lang="en">
    <head>
        <title>Mask layers</title>
        <meta charset="UTF-8" />
        <meta name="name" content="mask_layer" />
        <meta name="description" content="Illustrates the use of mask layers." />
        <meta name="viewport" content="width=device-width, initial-scale=1.0" />

        <link rel="icon" href="https://giro3d.org/images/favicon.svg" />
        <link href="https://giro3d.org/assets/bootstrap-custom.css" rel="stylesheet" />
        <script src="https://giro3d.org/assets/bootstrap.bundle.min.js"></script>
        <link
            rel="stylesheet"
            type="text/css"
            href="https://giro3d.org/latest/css/example.css"
        />

        <style>
        #viewerDiv canvas {
          background-image: linear-gradient(45deg, #aaaaaa 25%, transparent 25%),
            linear-gradient(-45deg, #aaaaaa 25%, transparent 25%),
            linear-gradient(45deg, transparent 75%, #aaaaaa 75%),
            linear-gradient(-45deg, transparent 75%, #aaaaaa 75%);
          background-size: 20px 20px;
          background-position:
            0 0,
            0 10px,
            10px -10px,
            -10px 0px;
        }
        </style>
    </head>

    <body>
        <div id="viewerDiv" class="m-0 p-0 w-100 h-100"></div>
        <div id="panelDiv" class="position-absolute top-0 start-0 mh-100 overflow-auto"></div>

        <div class="side-pane-with-status-bar">
            <div class="card">
                <h5 class="card-header">Mask layer</h5>

                <div class="card-body">
                    <form>
                        <div class="row">
                            <div class="dropdown">
                                <select
                                    class="btn btn-primary dropdown-toggle"
                                    id="layerState"
                                    autocomplete="off"
                                >
                                    <option value="0">Disabled</option>
                                    <option value="1" selected>Enabled</option>
                                    <option value="2">Enabled (invert mask)</option>
                                </select>
                            </div>
                        </div>
                    </form>
                </div>
            </div>
        </div>

        <script type="module" src="index.js"></script>
        <script>
            /* activate popovers */
            const popoverTriggerList = [].slice.call(
                document.querySelectorAll('[data-bs-toggle="popover"]'),
            );
            popoverTriggerList.map(
                // bootstrap is used as script in the template, disable warning about undef
                // eslint-disable-next-line no-undef
                popoverTriggerEl =>
                    new bootstrap.Popover(popoverTriggerEl, {
                        trigger: 'hover',
                        placement: 'left',
                        content: document.getElementById(
                            popoverTriggerEl.getAttribute('data-bs-content'),
                        ).innerHTML,
                        html: true,
                    }),
            );
        </script>
    </body>
</html>
package.json
{
    "name": "mask_layer",
    "dependencies": {
        "@giro3d/giro3d": "0.37.2"
    },
    "devDependencies": {
        "vite": "^3.2.3"
    },
    "scripts": {
        "start": "vite",
        "build": "vite build"
    }
}