Illustrates no-data elimination at the edges of a dataset after reprojection.

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100% © U.S. Geological Survey

The shown dataset does not have any no-data pixels. However, reprojecting it to a different CRS leaves empty areas at the edge, which become no-data areas. This example checks that those new no-data areas are correctly handled by the no-data filling algorithm.

index.js
import colormap from 'colormap';

import { Box3Helper, Color } from 'three';
import { MapControls } from 'three/examples/jsm/controls/MapControls.js';

import Extent from '@giro3d/giro3d/core/geographic/Extent.js';
import CogSource from '@giro3d/giro3d/sources/CogSource.js';
import Instance from '@giro3d/giro3d/core/Instance.js';
import ElevationLayer from '@giro3d/giro3d/core/layer/ElevationLayer';
import Map from '@giro3d/giro3d/entities/Map';
import Inspector from '@giro3d/giro3d/gui/Inspector.js';
import ColorMap, { ColorMapMode } from '@giro3d/giro3d/core/layer/ColorMap.js';

// Define projection that we will use (taken from https://epsg.io/26910, Proj4js section)
Instance.registerCRS(
    'EPSG:32742',
    '+proj=utm +zone=42 +south +datum=WGS84 +units=m +no_defs +type=crs',
);

const datasetExtent = new Extent(
    'EPSG:3857',
    -13581040.085,
    -13469591.026,
    5780261.83,
    5942165.048,
);

const extent = datasetExtent.clone().as('EPSG:32742');

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

// Instantiate Giro3D
const instance = new Instance(viewerDiv, {
    crs: extent.crs(),
});

// Instantiate the camera
instance.camera.camera3D.position.set(1305865, 24791965, 243407);

// Instantiate the controls
const controls = new MapControls(instance.camera.camera3D, instance.domElement);
controls.enableDamping = true;
controls.dampingFactor = 0.2;
controls.target.set(1305865, 24791964, 1000);
instance.useTHREEControls(controls);

// Use an elevation COG with nodata values
const source = new CogSource({
    // https://pubs.er.usgs.gov/publication/ds904
    url: 'https://3d.oslandia.com/cog_data/COG_EPSG3857_USGS_13_n47w122_20220919.tif',
    crs: 'EPSG:3857',
});

const values = colormap({ colormap: 'viridis', nshades: 256 });
const colors = values.map(v => new Color(v));

const min = 263;
const max = 4347;

const colorMap = new ColorMap(colors, min, max, ColorMapMode.Elevation);

const noDataOptions = {
    alpha: 0,
    maxSearchDistance: Infinity,
    replaceNoData: true,
};

const elevationLayer = new ElevationLayer({
    name: 'elevation',
    extent,
    source,
    noDataOptions,
    colorMap,
    minmax: { min, max },
});

const map = new Map('map', {
    extent,
    doubleSided: true,
    backgroundOpacity: 0,
    hillshading: true,
    discardNoData: true,
});

instance.add(map);

map.addLayer(elevationLayer);

const box = extent.toBox3(min, min);
const boxHelper = new Box3Helper(box, new Color('yellow'));
instance.add(boxHelper);
boxHelper.updateMatrixWorld();

// Attach the inspector
Inspector.attach(document.getElementById('panelDiv'), instance);

// Bind events

const enableFillNoDataCheckbox = document.getElementById('enableFillNoData');
enableFillNoDataCheckbox.oninput = function oninput() {
    const state = enableFillNoDataCheckbox.checked;
    map.materialOptions.discardNoData = state;
    instance.notifyChange(map);
};
index.html
<!doctype html>
<html lang="en">
    <head>
        <title>No-data elimination after reprojection</title>
        <meta charset="UTF-8" />
        <meta name="name" content="cog_nodata_reprojection" />
        <meta name="description" content="Illustrates no-data elimination at the edges of a dataset after reprojection." />
        <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/next/css/example.css"
        />

        
    </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">
                <div class="card-header">Options</div>

                <div class="card-body" id="options">
                    <div class="form-check form-switch">
                        <input
                            class="form-check-input"
                            type="checkbox"
                            checked="true"
                            role="switch"
                            id="enableFillNoData"
                            autocomplete="off"
                        />
                        <label class="form-check-label" for="enableFillNoData">Hide no-data pixels</label>
                    </div>
                </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": "cog_nodata_reprojection",
    "dependencies": {
        "colormap": "^2.3.2",
        "@giro3d/giro3d": "git+https://gitlab.com/giro3d/giro3d.git"
    },
    "devDependencies": {
        "vite": "^3.2.3"
    },
    "scripts": {
        "start": "vite",
        "build": "vite build"
    }
}