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

Options

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,
    5780261.830, 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,
    segments: 128,
});

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>
  <meta charset="UTF-8">
  <title>Giro3D - No-data elimination after reprojection</title>
  <link href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.2/dist/css/bootstrap.min.css" rel="stylesheet" integrity="sha384-T3c6CoIi6uLrA9TneNEoa7RxnatzjcDSCmG1MXxSR1GAsXEV/Dwwykc2MPK8M2HN" crossorigin="anonymous">
  <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap-icons@1.11.3/font/bootstrap-icons.min.css">
  <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.2/dist/js/bootstrap.bundle.min.js" integrity="sha384-C6RzsynM9kWDrMNeT87bh95OGNyZPhcTNXj1NW7RuBCsyN/o0jlpcV8Qyq46cDfL" crossorigin="anonymous"></script>
  <style>
    body {
      padding: 0;
      margin: 0;
      width: 100vw;
      height: 100vh;
    }

    #viewerDiv {
      width: 100%;
      height: 100%;
    }

    #panelDiv {
      position: absolute;
      top: 0;
      left: 0;
    }
    
  </style>
</head>

<body>
  <div id="viewerDiv"></div>
  <div id="panelDiv"></div>
  <div class="m-2 position-absolute top-0 end-0">

    <div class="card m-1">
        <div class="card-header">Options</div>

        <fieldset class="container m-1" id="options">

            <div class="mb-3">
                <div class="form-check form-switch">
                    <input class="form-check-input" type="checkbox" checked="true" role="switch" id="enableFillNoData">
                    <label class="form-check-label" for="enableFillNoData">Hide no-data pixels</label>
                </div>
            </div>

        </fieldset>
    </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": {
    "@giro3d/giro3d": "0.33.1"
  },
  "devDependencies": {
    "vite": "^3.2.3"
  },
  "scripts": {
    "start": "vite",
    "build": "vite build"
  }
}