cesiumjs-3d-tiles

# CesiumJS 3D Tiles

Version baseline: CesiumJS v1.142 (ES module imports, async factory methods).

## Loading a Tileset

Always use async factory methods -- never call the constructor directly.

```js
import { Cesium3DTileset, HeadingPitchRange, Math as CesiumMath } from "cesium";

// From a URL
const tileset = await Cesium3DTileset.fromUrl(
  "https://example.com/tileset.json",
  { maximumScreenSpaceError: 16 }, // lower = higher quality
);
viewer.scene.primitives.add(tileset);
viewer.zoomTo(tileset, new HeadingPitchRange(
  0.0, CesiumMath.toRadians(-25.0), tileset.boundingSphere.radius * 2.0,
));
```

```js
// From Cesium ion
const tileset = await Cesium3DTileset.fromIonAssetId(75343);
viewer.scene.primitives.add(tileset);
```

```js
// Google Photorealistic 3D Tiles
import { createGooglePhotorealistic3DTileset } from "cesium";
const google3D = await createGooglePhotorealistic3DTileset({
  onlyUsingWithGoogleGeocoder: true,
});
viewer.scene.primitives.add(google3D);
```

```js
// OSM Buildings
import { createOsmBuildingsAsync } from "cesium";
const osmBuildings = await createOsmBuildingsAsync();
viewer.scene.primitives.add(osmBuildings);
```

## Key Constructor Options

| Option | Default | Purpose |
|--------|---------|---------|
| `maximumScreenSpaceError` | 16 | LOD quality threshold (pixels) |
| `cacheBytes` | 536870912 | Tile cache trim target (bytes) |
| `maximumCacheOverflowBytes` | 536870912 | Extra cache headroom |
| `shadows` | ShadowMode.ENABLED | Shadow casting/receiving |
| `modelMatrix` | Matrix4.IDENTITY | Root transform |
| `clippingPlanes` | undefined | ClippingPlaneCollection |
| `clippingPolygons` | undefined | ClippingPolygonCollection (WebGL 2) |
| `enableCollision` | false | Camera collision with tileset surface |
| `pointCloudShading` | undefined | Point attenuation options object |
| `classificationType` | undefined | TERRAIN, CESIUM_3D_TILE, or BOTH |
| `dynamicScreenSpaceError` | true | Horizon LOD optimization |
| `foveatedScreenSpaceError` | true | Center-screen tile priority |
| `preloadFlightDestinations` | true | Prefetch tiles at flight target |
| `featureIdLabel` | "featureId_0" | EXT_mesh_features ID set label |
| `backFaceCulling` | true | Cull back faces per glTF material |
| `edgeDisplayMode` | EdgeDisplayMode.SURFACES_ONLY | Render glTF edge-visibility data when present |

## Mapbox Vector Tiles as Runtime 3D Tiles (Experimental, 1.142+)

`MVTDataProvider` loads `{z}/{x}/{y}` Mapbox Vector Tile `.mvt`/`.pbf`
templates and converts tile payloads into runtime 3D Tiles. Use it when vector
data is naturally tiled and you want 3D Tiles styling, metadata picking, and LOD
instead of a single GeoJSON primitive.

For one in-memory or URL-backed GeoJSON object, prefer `GeoJsonPrimitive` in
`cesiumjs-primitives`. For Entity/DataSource conveniences, prefer
`GeoJsonDataSource` in `cesiumjs-entities`.

```js
import {
  Cesium3DTileStyle,
  MVTDataProvider,
  Rectangle,
} from "cesium";

const provider = await MVTDataProvider.fromUrl(
  "https://example.com/tiles/{z}/{x}/{y}.pbf",
  {
    minZoom: 4,
    maxZoom: 14,
    extent: Rectangle.fromDegrees(-125, 24, -66, 50),
    featureIdProperty: "id",
  },
);

viewer.scene.primitives.add(provider);

// The provider owns a generated Cesium3DTileset.
provider.tileset.style = new Cesium3DTileStyle({
  color: {
    conditions: [
      ["${kind} === 'park'", "color('seagreen', 0.65)"],
      ["${kind} === 'water'", "color('steelblue', 0.55)"],
      ["true", "color('white', 0.45)"],
    ],
  },
});
```

Feature properties are encoded as `EXT_structural_metadata`, so standard
3D Tiles styling and picking patterns apply:

```js
const picked = viewer.scene.pick(windowPosition);
if (picked && typeof picked.getProperty === "function") {
  console.log(picked.getProperty("name"));
}
```

Notes:
- URL templates must contain `{z}`, `{x}`, and `{y}` placeholders; tile URLs are parsed from `/z/x/y`.
- Empty 204/404 tiles are treated as missing instead of hard failures.
- `provider.show` proxies visibility to the generated tileset.
- Runtime vector glTF content uses draft `EXT_mesh_polygon` and `3DTILES_content_gltf_vector` support; treat this path as experimental.

## Tileset Events

```js
tileset.loadProgress.addEventListener((pending, processing) => {
  if (pending === 0 && processing === 0) console.log("Loaded");
});
tileset.initialTilesLoaded.addEventListener(() => { /* first view ready */ });
tileset.allTilesLoaded.addEventListener(() => { /* all visible tiles ready */ });
tileset.tileLoad.addEventListener((tile) => { /* tile content loaded */ });
tileset.tileUnload.addEventListener((tile) => { /* tile evicted from cache */ });
tileset.tileFailed.addEventListener(({ url, message }) => {
  console.error(`Tile ${url}: ${message}`);
});
// Per-frame manual styling
tileset.tileVisible.addEventListener((tile) => {
  const content = tile.content;
  for (let i = 0; i < content.featuresLength; i++) {
    content.getFeature(i).color = Cesium.Color.fromRandom();
  }
});
```

## Runtime Properties

```js
tileset.show = false;                     // toggle visibility
tileset.maximumScreenSpaceError = 8;      // increase quality
const { center, radius } = tileset.boundingSphere;

import { Matrix4, Cartesian3 } from "cesium";
tileset.modelMatrix = Matrix4.fromTranslation(new Cartesian3(0, 0, 100));
```

## Declarative Styling

Assign a `Cesium3DTileStyle` to `tileset.style`. Expressions reference feature
properties with `${PropertyName}`.

```js
import { Cesium3DTileStyle } from "cesium";

// Color by height conditions
tileset.style = new Cesium3DTileStyle({
  color: {
    conditions: [
      ["${Height} >= 100", "color('purple', 0.5)"],
      ["${Height} >= 50",  "color('red')"],
      ["true",             "color('blue')"],
    ],
  },
  show: "${Height} > 0",
});
```

```js
// Use defines to simplify repeated sub-expressions
tileset.style = new Cesium3DTileStyle({
  defines: { material: "${feature['building:material']}" },
  color: {