Assign various blending modes to a color layer.

Parameters
100% © Mapbox, © OpenStreetMap contributors, © NASA

Color layers can have different blending modes depending on the desired effect. The default blending mode (

BlendingMode.Normal
) is alpha blending, where the transparency of the pixels is used to blend the layer with the previous layer (or the background).

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

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

import Extent from "@giro3d/giro3d/core/geographic/Extent.js";
import Instance from "@giro3d/giro3d/core/Instance.js";
import Map from "@giro3d/giro3d/entities/Map.js";
import ColorLayer from "@giro3d/giro3d/core/layer/ColorLayer.js";
import BlendingMode from "@giro3d/giro3d/core/layer/BlendingMode.js";
import TiledImageSource from "@giro3d/giro3d/sources/TiledImageSource.js";
import Inspector from "@giro3d/giro3d/gui/Inspector.js";
import StaticImageSource from "@giro3d/giro3d/sources/StaticImageSource.js";
import VectorSource from "@giro3d/giro3d/sources/VectorSource.js";

function bindNumericalDropDown(id, onChange) {
  const element = document.getElementById(id);
  if (!(element instanceof HTMLSelectElement)) {
    throw new Error(
      "invalid binding element: expected HTMLSelectElement, got: " +
        element.constructor.name,
    );
  }

  element.onchange = () => {
    onChange(parseInt(element.value));
  };

  const callback = (v) => {
    element.value = v.toString();
    onChange(parseInt(element.value));
  };

  return [callback, parseInt(element.value), element];
}

function bindButton(id, onClick) {
  const element = document.getElementById(id);
  if (!(element instanceof HTMLButtonElement)) {
    throw new Error(
      "invalid binding element: expected HTMLButtonElement, got: " +
        element.constructor.name,
    );
  }

  element.onclick = () => {
    onClick(element);
  };

  return element;
}

function bindColorPicker(id, onChange) {
  const element = document.getElementById(id);
  if (!(element instanceof HTMLInputElement)) {
    throw new Error(
      "invalid binding element: expected HTMLInputElement, got: " +
        element.constructor.name,
    );
  }

  element.oninput = function oninput() {
    // Let's change the classification color with the color picker value
    const hexColor = element.value;
    onChange(new Color(hexColor));
  };

  const externalFunction = (v) => {
    element.value = `#${new Color(v).getHexString()}`;
    onChange(element.value);
  };

  return [externalFunction, new Color(element.value), element];
}

function bindToggle(id, onChange) {
  const element = document.getElementById(id);
  if (!(element instanceof HTMLInputElement)) {
    throw new Error(
      "invalid binding element: expected HTMLButtonElement, got: " +
        element.constructor.name,
    );
  }

  element.oninput = function oninput() {
    onChange(element.checked);
  };

  const callback = (v) => {
    element.checked = v;
    onChange(element.checked);
  };

  return [callback, element.checked, element];
}

const instance = new Instance({
  target: "view",
  crs: "EPSG:4326",
});

const extent = new Extent("EPSG:4326", -180, 180, -90, 90);

const map = new Map({ extent, backgroundColor: "blue" });

instance.add(map);

const key =
  "pk.eyJ1IjoidG11Z3VldCIsImEiOiJjbGJ4dTNkOW0wYWx4M25ybWZ5YnpicHV6In0.KhDJ7W5N3d1z3ArrsDjX_A";

// Create a satellite layer with no blending at all (layer is completely opaque)
const satellite = new ColorLayer({
  name: "satellite",
  blendingMode: BlendingMode.None,
  source: new TiledImageSource({
    source: new XYZ({
      url: `https://api.mapbox.com/v4/mapbox.satellite/{z}/{x}/{y}.webp?access_token=${key}`,
      crossOrigin: "anonymous",
    }),
  }),
});
map.addLayer(satellite).catch((e) => console.error(e));

// Create a vector layer with normal blending mode.
const vector = new ColorLayer({
  name: "boundaries",
  blendingMode: BlendingMode.Normal,
  source: new VectorSource({
    data: {
      url: "https://3d.oslandia.com/giro3d/vectors/countries.geojson",
      format: new GeoJSON(),
    },
    style: new Style({
      stroke: new Stroke({ color: "red", width: 2 }),
    }),
    dataProjection: "EPSG:4326",
  }),
});
map.addLayer(vector).catch((e) => console.error(e));

// Create a cloud coverage layer with an additive blending mode
const cloud = new ColorLayer({
  name: "clouds",
  blendingMode: BlendingMode.Add,
  source: new StaticImageSource({
    source: "https://3d.oslandia.com/giro3d/images/cloud_cover.webp",
    extent,
  }),
});
map.addLayer(cloud).catch((e) => console.error(e));

instance.view.camera.position.set(0, 0, 230);

const controls = new MapControls(instance.view.camera, instance.domElement);

instance.view.setControls(controls);

// Example GUI

const [setBackground] = bindColorPicker("color", (v) => {
  map.backgroundColor = v;
  instance.notifyChange(map);
});
const setMode = (layer, mode) => {
  layer.blendingMode = mode;
  instance.notifyChange(layer);
};
const [setCloudMode] = bindNumericalDropDown("cloud", (v) => setMode(cloud, v));
const [setVectorMode] = bindNumericalDropDown("vector", (v) =>
  setMode(vector, v),
);
const [setSatelliteMode] = bindNumericalDropDown("satellite", (v) =>
  setMode(satellite, v),
);

const show = (layer, v) => {
  layer.visible = v;
  instance.notifyChange(layer);
};
const [showClouds] = bindToggle("show-cloud", (v) => show(cloud, v));
const [showSatellite] = bindToggle("show-satellite", (v) => show(satellite, v));
const [showVector] = bindToggle("show-vector", (v) => show(vector, v));
const [showBackground] = bindToggle("show-background", (v) => {
  map.backgroundOpacity = v ? 1 : 0;
  instance.notifyChange(map);
});

const reset = () => {
  setCloudMode(BlendingMode.Add);
  setVectorMode(BlendingMode.Normal);
  setSatelliteMode(BlendingMode.None);

  showClouds(true);
  showVector(true);
  showSatellite(true);

  setBackground("blue");

  showBackground(true);
};

bindButton("reset", reset);

reset();

Inspector.attach("inspector", instance);
index.html
<!doctype html>
<html lang="en">
  <head>
    <title>Blending modes</title>
    <meta charset="UTF-8" />
    <meta name="name" content="layer_blending_modes" />
    <meta
      name="description"
      content="Assign various blending modes to a color layer."
    />
    <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"
    />
  </head>

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

    <div class="side-pane-with-status-bar">
      <!--Parameters -->
      <div class="card">
        <div class="card-header">
          Parameters
          <button
            type="button"
            id="reset"
            class="btn btn-sm btn-primary rounded float-end"
          >
            reset
          </button>
        </div>

        <div class="card-body">
          <!-- Cloud layer -->
          <div class="input-group mb-3">
            <div class="input-group-text">
              <input
                class="form-check-input"
                type="checkbox"
                checked="true"
                role="switch"
                id="show-cloud"
                autocomplete="off"
              />
            </div>
            <label class="input-group-text" style="width: 8rem" for="cloud"
              >Cloud layer</label
            >
            <select class="form-select" id="cloud" autocomplete="off">
              <option value="0">None</option>
              <option value="1">Normal</option>
              <option value="2" selected>Add</option>
              <option value="3">Multiply</option>
            </select>
          </div>

          <!-- Vector layer -->
          <div class="input-group mb-3">
            <div class="input-group-text">
              <input
                class="form-check-input"
                type="checkbox"
                checked="true"
                role="switch"
                id="show-vector"
                autocomplete="off"
              />
            </div>
            <label class="input-group-text" style="width: 8rem" for="vector"
              >Vector layer</label
            >
            <select class="form-select" id="vector" autocomplete="off">
              <option value="0">None</option>
              <option value="1" selected>Normal</option>
              <option value="2">Add</option>
              <option value="3">Multiply</option>
            </select>
          </div>

          <!-- Satellite layer -->
          <div class="input-group mb-3">
            <div class="input-group-text">
              <input
                class="form-check-input"
                type="checkbox"
                checked="true"
                role="switch"
                id="show-satellite"
                autocomplete="off"
              />
            </div>
            <label class="input-group-text" style="width: 8rem" for="satellite"
              >Satellite layer</label
            >
            <select class="form-select" id="satellite" autocomplete="off">
              <option value="0" selected>None</option>
              <option value="1">Normal</option>
              <option value="2">Add</option>
              <option value="3">Multiply</option>
            </select>
          </div>

          <!-- Background color -->
          <div class="input-group">
            <div class="input-group-text">
              <input
                class="form-check-input"
                type="checkbox"
                checked="true"
                role="switch"
                id="show-background"
                autocomplete="off"
              />
            </div>
            <label class="input-group-text" style="width: 8rem" for="color"
              >Background</label
            >
            <input
              type="color"
              class="form-control form-control-color"
              id="color"
              value="#2978b4"
              title="color"
            />
          </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": "layer_blending_modes",
    "dependencies": {
        "@giro3d/giro3d": "0.39.0"
    },
    "devDependencies": {
        "vite": "^3.2.3"
    },
    "scripts": {
        "start": "vite",
        "build": "vite build"
    }
}