Cesiumjs Core Utilities

CesiumJS Core Utilities & Networking

Version baseline: CesiumJS v1.139+ (ES module imports, defaultValue removed in v1.134)

Breaking Change: defaultValue Removed (v1.134)

// WRONG (removed in v1.134)
const name = defaultValue(options.name, "default");
const opts = defaultValue(options, defaultValue.EMPTY_OBJECT);

// CORRECT (v1.134+)
import { Frozen } from "cesium";
const name = options.name ?? "default";
const opts = options ?? Frozen.EMPTY_OBJECT;

Frozen.EMPTY_OBJECT is Object.freeze({}) and Frozen.EMPTY_ARRAY is Object.freeze([]). Use them as safe defaults for options objects and array parameters.

Resource: HTTP Requests and Data Fetching

Resource is the unified class for all HTTP operations. It wraps URL construction, query parameters, headers, proxying, and retry logic.

Fetching Data

import { Resource } from "cesium";

// Static shorthand: accepts a URL string or options object
const jsonData = await Resource.fetchJson({ url: "https://api.example.com/data.json" });

// Instance-based: construct once, reuse for multiple fetches
const resource = new Resource({
  url: "https://api.example.com/features",
  queryParameters: { format: "json", limit: "100" },
  headers: { "Authorization": "Bearer my-token" },
});
const features = await resource.fetchJson();
const text = await resource.fetchText();           // string
const buffer = await resource.fetchArrayBuffer();  // ArrayBuffer
const blob = await resource.fetchBlob();           // Blob
const image = await resource.fetchImage();         // HTMLImageElement or ImageBitmap

Derived Resources and Template Values

import { Resource } from "cesium";

const api = new Resource({
  url: "https://tiles.example.com/{version}/tiles/{z}/{x}/{y}.png",
  templateValues: { version: "v2" },
  headers: { "X-Api-Key": "abc123" },
});

// getDerivedResource inherits headers, proxy, and retry settings
const tile = api.getDerivedResource({
  templateValues: { z: "10", x: "512", y: "384" },
});
const tileImage = await tile.fetchImage();

// Modify query parameters on an existing resource
resource.setQueryParameters({ access_token: "new-token" });
resource.appendQueryParameters({ extra: "param" });

Retry and Proxy

import { Resource, DefaultProxy } from "cesium";

// Retry on specific HTTP status codes
const resource = new Resource({
  url: "https://api.example.com/unstable",
  retryAttempts: 3,
  retryCallback: (resource, error) => {
    if (error.statusCode === 429) {
      return new Promise((resolve) => setTimeout(() => resolve(true), 2000));
    }
    return false;
  },
});

// DefaultProxy appends the target URL as a query parameter
const proxied = new Resource({
  url: "https://external-server.com/data.json",
  proxy: new DefaultProxy("/proxy/"),
});
// Request goes to: /proxy/?https%3A%2F%2Fexternal-server.com%2Fdata.json

POST and PUT

import { Resource } from "cesium";

const resource = new Resource({ url: "https://api.example.com/upload" });
const result = await resource.post(JSON.stringify({ name: "test" }), {
  headers: { "Content-Type": "application/json" },
});
// resource.put() works the same way

Color

RGBA components as floats [0.0, 1.0]. Over 140 named constants as frozen static properties (e.g., Color.RED, Color.CORNFLOWERBLUE, Color.TRANSPARENT).

Creating Colors

import { Color } from "cesium";

const red = Color.RED;                                        // frozen constant
const custom = new Color(0.2, 0.6, 0.8, 1.0);               // float constructor
const blue = Color.fromCssColorString("#3498db");             // hex string
const semiRed = Color.fromCssColorString("rgba(255,0,0,0.5)"); // CSS rgba()
const coral = Color.fromBytes(255, 127, 80, 255);            // 0-255 bytes
const hsl = Color.fromHsl(0.58, 0.8, 0.5, 1.0);             // hue/sat/light
const bright = Color.fromRandom({                             // constrained random
  minimumRed: 0.75, minimumGreen: 0.75, minimumBlue: 0.75, alpha: 1.0,
});

Manipulation and Conversion

import { Color } from "cesium";

const base = Color.fromCssColorString("#3498db");
const translucent = base.withAlpha(0.5);                // new Color with alpha
const lighter = base.brighten(0.3, new Color());        // requires result param
const darker = base.darken(0.3, new Color());
const css = base.toCssColorString();                    // "rgb(52,152,219)"
const hex = base.toCssHexString();                      // "#3498db"
const bytes = base.toBytes();                           // [52, 152, 219, 255]
const equal = Color.RED.equals(new Color(1.0, 0.0, 0.0, 1.0)); // true

Event System

Event is the publish-subscribe mechanism used throughout CesiumJS. Classes expose Event properties like Viewer.selectedEntityChanged and Cesium3DTileset.tileLoad.

Basic Usage

import { Event } from "cesium";

const Event();

// addEventListener returns a removal function
const removeListener = onDataReceived.addEventListener((data) => {
  console.log("Received:", data);
});

onDataReceived.raiseEvent({ id: 1, value: "test" }); // invoke all listeners
removeListener(); // unsubscribe

EventHelper for Batch Cleanup

import { EventHelper } from "cesium";

const helper = new EventHelper();
helper.add(viewer.selectedEntityChanged, (entity) => {
  console.log("Selected:", entity?.name);
});
helper.add(viewer.clock.onTick, (clock) => { /* per-frame logic */ });
helper.add(viewer.scene.globe.tileLoadProgressEvent, (queueLength) => {
  console.log("Tiles loading:", queueLength);
});

// Remove all listeners at once (e.g., in a destroy method)
helper.removeAll();

RequestScheduler Configuration

RequestScheduler is a singleton that manages concurrent request limits. Request objects represent individual HTTP requests with priority and throttling (primarily internal).

import { RequestScheduler } from "cesium";

RequestScheduler.maximumRequests = 64;            // global max (default: 50)
RequestScheduler.maximumRequestsPerServer = 12;   // per-server max (default: 18)

// Override for known HTTP/2 servers
RequestScheduler.requestsByServer = {
  "api.cesium.com:443": 32,
  "assets.cesium.com:443": 32,
};

Error Handling

• DeveloperError -- bug in calling code (invalid args). Thrown only in debug builds; fix the code, do not catch.
• RuntimeError -- runtime failure (network, shader compile). Catch in production.

import { RuntimeError, formatError, Cesium3DTileset } from "cesium";

try {
  const tileset = await Cesium3DTileset.fromUrl("https://example.com/tileset.json");
  viewer.scene.primitives.add(tileset);
} catch (error) {
  if (error instanceof RuntimeError) {
    console.error("Failed to load tileset:", error.message);
  } else {
    console.error(formatError(error)); // extracts name, message, stack
  }
}

Helper Functions

defined, clone, combine

import { defined, clone, combine } from "cesium";

// defined: returns true if value is neither null nor undefined
if (defined(entity.billboard)) {
  entity.billboard.scale = 2.0;
}

// clone: shallow by default, pass true for deep
const obj = clone({ a: 1, nested: { b: 2 } }, true);

// combine: merge objects, first arg's keys take precedence
const merged = combine({ size: 20 }, { size: 10, color: "red" });
// { size: 20, color: "red" }

createGuid, buildModuleUrl

import { createGuid, buildModuleUrl } from "cesium";

const id = createGuid(); // "xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx"

// Resolve paths relative to Cesium installation
const iconUrl = buildModuleUrl("Assets/Textures/maki/marker.png");

URL Utilities

import { objectToQuery, queryToObject, getExtensionFromUri, getBaseUri } from "cesium";

const qs = objectToQuery({ key1: "value 1", key2: ["x", "y"] });
// "key1=value%201&key2=x&key2=y"

const parsed = queryToObject("key1=value%201&key2=x&key2=y");
// { key1: "value 1", key2: ["x", "y"] }

getExtensionFromUri("https://example.com/model.glb?v=2"); // "glb"
getBaseUri("https://example.com/data/model.glb");          // "https://example.com/data/"

destroyObject

Replaces all methods on an object with functions that throw DeveloperError, and sets isDestroyed() to return true. Standard cleanup pattern for objects holding native resources.

import { destroyObject } from "cesium";

class MyWidget {
  constructor(viewer) {
    this._handler = new Cesium.ScreenSpaceEventHandler(viewer.canvas);
  }
  isDestroyed() { return false; }
  destroy() {
    this._handler.destroy();
    return destroyObject(this);
  }
}

AssociativeArray

O(1) key lookup with a live values array for allocation-free iteration in render loops.

import { AssociativeArray } from "cesium";

const items = new AssociativeArray();
items.set("building-1", { height: 50 });
items.set("building-2", { height: 80 });

items.get("building-1");       // { height: 50 }
items.contains("building-1");  // true

// Iterate without per-frame allocations
const values = items.values;
for (let i = 0; i < values.length; i++) { /* process values[i] */ }

items.remove("building-1");
items.removeAll();

PinBuilder

Generates map pin canvas elements with colors, text, maki icons, or custom images.

import { PinBuilder, Color, Cartesian3, VerticalOrigin } from "cesium";

const pin = new PinBuilder();
const redPin = pin.fromColor(Color.RED, 48);                         // solid color
const textPin = pin.fromText("A", Color.BLUE, 48);                   // text label
const iconPin = await pin.fromMakiIconId("hospital", Color.GREEN, 48); // maki icon
const urlPin = await pin.fromUrl("/icons/custom.png", Color.YELLOW, 48);

viewer.entities.add({
  position: Cartesian3.fromDegrees(-75.17, 39.95),
  billboard: {
    image: pin.fromText("1", Color.ROYALBLUE, 48),
    verticalOrigin: VerticalOrigin.BOTTOM,
  },
});

DistanceDisplayCondition

Controls entity/billboard/label visibility based on camera distance.

import { DistanceDisplayCondition, Cartesian3, Color } from "cesium";

viewer.entities.add({
  position: Cartesian3.fromDegrees(-75.17, 39.95),
  billboard: {
    image: "/icons/marker.png",
    distanceDisplayCondition: new DistanceDisplayCondition(100.0, 50000.0),
  },
});

Feature Detection and Fullscreen

import { FeatureDetection, Fullscreen } from "cesium";

if (FeatureDetection.supportsWebAssembly()) { /* WASM workers OK */ }
if (FeatureDetection.supportsTypedArrays()) { /* TypedArrays OK */ }

if (Fullscreen.supportsFullscreen()) {
  Fullscreen.requestFullscreen(viewer.container);
}

TaskProcessor

Wraps Web Workers for background computation. Worker is created lazily on first scheduleTask.

import { TaskProcessor, defined } from "cesium";

const processor = new TaskProcessor("myWorkerModule");
const promise = processor.scheduleTask({ data: largeArray, op: "simplify" });

if (!defined(promise)) {
  // Too many active tasks; retry next frame
} else {
  const result = await promise;
}
processor.destroy(); // release worker when done

TrustedServers

Credentials (cookies, auth headers) are sent only to registered servers.

import { TrustedServers } from "cesium";

TrustedServers.add("secure-tiles.example.com", 443);
TrustedServers.contains("https://secure-tiles.example.com/tileset.json"); // true
TrustedServers.remove("secure-tiles.example.com", 443);

Performance Tips

1. Reuse Resource instances -- getDerivedResource inherits proxy, headers, and retry config without re-parsing the URL.
2. Tune RequestScheduler for HTTP/2 -- increase maximumRequests and per-server limits via requestsByServer for faster tile loading.
3. Use Frozen.EMPTY_OBJECT for defaults -- avoids allocating a new {} on every call in hot paths.
4. Prefer defined() over truthiness -- correctly distinguishes 0, "", and false from null/undefined.
5. Use AssociativeArray in render loops -- its values array avoids per-frame Object.keys() allocations.
6. Set retryAttempts conservatively -- gate retries on specific status codes (401, 429, 503) via retryCallback.
7. Destroy TaskProcessors when done -- idle workers still consume memory.
8. Never mutate frozen Color constants -- call .clone() or .withAlpha() first.
9. Use formatError in catch blocks -- extracts name, message, and stack from any error type.
10. Cache PinBuilder output -- store canvas references when generating many identical pins across frames.

See Also

• cesiumjs-viewer-setup -- Viewer initialization, Ion token, scene configuration
• cesiumjs-imagery -- Imagery providers that consume Resource for tile fetching
• cesiumjs-entities -- Entity API using Color, DistanceDisplayCondition, and PinBuilder