cesiumjs-viewer-setup

# CesiumJS Viewer & Scene Setup

Reference for bootstrapping CesiumJS applications: Viewer, CesiumWidget, Ion/GoogleMaps/ITwinPlatform configuration, widgets, factory helpers, geocoder services, viewer mixins, Credits, and related enums.

## Quick Start

```js
import { Ion, Viewer, Terrain } from "cesium";
import "cesium/Build/Cesium/Widgets/widgets.css";

// Always set your Ion token before any other Cesium calls
Ion.defaultAccessToken = "YOUR_CESIUM_ION_ACCESS_TOKEN";

const viewer = new Viewer("cesiumContainer", {
  terrain: Terrain.fromWorldTerrain(),
});
```

Required HTML: `<div id="cesiumContainer" style="width:100%;height:100vh"></div>`

## Ion & Platform Configuration

### Cesium Ion

```js
import { Ion } from "cesium";

Ion.defaultAccessToken = "YOUR_TOKEN";  // required for ion assets
Ion.defaultServer = "https://your-ion-server.example.com/"; // optional: self-hosted
```

### IonResource

```js
import { IonResource, Cesium3DTileset } from "cesium";

const resource = await IonResource.fromAssetId(96188);
const tileset = await Cesium3DTileset.fromUrl(resource);
viewer.scene.primitives.add(tileset);
```

### Google Maps Platform

```js
import { GoogleMaps, createGooglePhotorealistic3DTileset, Viewer, IonGeocodeProviderType } from "cesium";

GoogleMaps.defaultApiKey = "YOUR_GOOGLE_MAPS_API_KEY"; // optional: without key, served via ion

const viewer = new Viewer("cesiumContainer", {
  geocoder: IonGeocodeProviderType.GOOGLE, // required with Google 3D Tiles
});

const tileset = await createGooglePhotorealistic3DTileset({
  onlyUsingWithGoogleGeocoder: true,
});
viewer.scene.primitives.add(tileset);
```

### iTwin Platform (experimental)

```js
import { ITwinPlatform, ITwinData } from "cesium";

ITwinPlatform.defaultAccessToken = "YOUR_ITWIN_TOKEN";
const tileset = await ITwinData.createTilesetForIModel(viewer, "imodel-id");

// 1.140+ (#13208): Reality Data of type GaussianSplat3DTiles is now supported
const splats = await ITwinData.createTilesetForRealityDataId(
  iTwinId,
  realityDataId,
  ITwinPlatform.RealityDataType.GaussianSplat3DTiles,
);
viewer.scene.primitives.add(splats);
```

## Viewer Constructor Options

`new Viewer(container, options?)` -- `container` is a DOM element or its string ID.

### Widget Toggles

| Option | Default | Purpose |
|--------|---------|---------|
| `animation` | `true` | Playback controls |
| `baseLayerPicker` | `true` | Imagery/terrain switcher |
| `fullscreenButton` | `true` | Fullscreen toggle |
| `vrButton` | `false` | WebVR toggle |
| `geocoder` | `IonGeocodeProviderType.DEFAULT` | Search bar (`false` to hide) |
| `homeButton` | `true` | Reset to home view |
| `infoBox` | `true` | Entity info popup |
| `sceneModePicker` | `true` | 2D/3D/Columbus toggle |
| `selectionIndicator` | `true` | Selection reticle |
| `timeline` | `true` | Time scrubber |
| `navigationHelpButton` | `true` | Mouse/touch help |
| `projectionPicker` | `false` | Perspective/ortho toggle |

### Scene & Rendering

| Option | Default | Purpose |
|--------|---------|---------|
| `sceneMode` | `SceneMode.SCENE3D` | Initial scene mode |
| `scene3DOnly` | `false` | Lock to 3D, saves GPU memory |
| `shadows` | `false` | Shadow casting |
| `terrainShadows` | `ShadowMode.RECEIVE_ONLY` | Terrain shadow mode |
| `requestRenderMode` | `false` | Render only on changes |
| `maximumRenderTimeChange` | `0.0` | Max sim-time delta for render |
| `msaaSamples` | `4` | MSAA (1 to disable) |
| `orderIndependentTranslucency` | `true` | Translucent ordering |
| `mapMode2D` | `MapMode2D.INFINITE_SCROLL` | 2D scroll behavior |

### Layers & Terrain

| Option | Default | Purpose |
|--------|---------|---------|
| `baseLayer` | `ImageryLayer.fromWorldImagery()` | Base imagery (`false` for none; needs `baseLayerPicker: false`) |
| `terrain` | none | Async terrain helper (cannot combine with `terrainProvider`) |
| `terrainProvider` | `EllipsoidTerrainProvider` | Sync terrain provider |
| `globe` | `new Globe()` | `false` for no globe (space scenes) |
| `skyBox` | auto (WGS84) | `false` disables sky/sun/moon |
| `skyAtmosphere` | auto (WGS84) | `false` disables limb glow |

### Minimal Viewer (No Widgets)

```js
import { Viewer, Ion, Terrain } from "cesium";
Ion.defaultAccessToken = "YOUR_TOKEN";

const viewer = new Viewer("cesiumContainer", {
  animation: false, baseLayerPicker: false, fullscreenButton: false,
  geocoder: false, homeButton: false, infoBox: false,
  sceneModePicker: false, selectionIndicator: false,
  timeline: false, navigationHelpButton: false,
  terrain: Terrain.fromWorldTerrain(),
});
```

## CesiumWidget (Lightweight Alternative)

No UI widgets, no Knockout dependency. Suitable for custom UIs or embedding.

```js
import { CesiumWidget, Ion } from "cesium";
Ion.defaultAccessToken = "YOUR_TOKEN";

const widget = new CesiumWidget("cesiumContainer", { shouldAnimate: true });
// Exposes: widget.scene, widget.camera, widget.entities
```

## SceneMode Enum

| Value | Description |
|-------|-------------|
| `SceneMode.SCENE3D` | Standard 3D globe (default) |
| `SceneMode.SCENE2D` | Top-down orthographic map |
| `SceneMode.COLUMBUS_VIEW` | 2.5D flat map with height |
| `SceneMode.MORPHING` | Transitioning between modes |

```js
import { Viewer, SceneMode } from "cesium";

const viewer = new Viewer("cesiumContainer", { sceneMode: SceneMode.SCENE2D });
viewer.scene.morphTo3D(2.0);          // animated transition
viewer.scene.morphToColumbusView(2.0);
```

## Scene Configuration

```js
const scene = viewer.scene;
scene.globe.depthTestAgainstTerrain = true; // entities interact with terrain
scene.globe.enableLighting = true;          // sun-based lighting

// Key sub-objects
scene.camera;           // Camera
scene.primitives;       // PrimitiveCollection
scene.groundPrimitives; // PrimitiveCollection (ground-clamped)
scene.imageryLayers;    // ImageryLayerCollection
scene.postProcessStages;

scene.requestRender();  // trigger frame in requestRenderMode
```

## Factory Helpers

### createOs