# BillboardCollection

#### new Cesium.BillboardCollection(options)
Scene/BillboardCollection.js 153

  A renderable collection of billboards. Billboards are viewport-aligned images positioned in the 3D scene.
  Example billboards
  Billboards are added and removed from the collection using `BillboardCollection#add` and `BillboardCollection#remove`. Billboards in a collection automatically share textures for images with the same identifier.

  ##### Performance:

  For best performance, prefer a few collections, each with many billboards, to many collections with only a few billboards each. Organize collections so that billboards with the same update frequency are in the same collection, i.e., billboards that do not change should be in one collection; billboards that change every frame should be in another collection; and so on.

  Name | Type | Description
  --- | --- | ---
  `options` | Object | optional Object with the following properties:
  Name | Type | Default | Description
  --- | --- | --- | ---
  `modelMatrix` | Matrix4 | `Matrix4.IDENTITY` | optional The 4x4 transformation matrix that transforms each billboard from model to world coordinates.
  `debugShowBoundingVolume` | Boolean | `false` | optional For debugging only. Determines if this primitive's commands' bounding spheres are shown.
  `scene` | Scene |  | optional Must be passed in for billboards that use the height reference property or will be depth tested against the globe.

  ##### Example:

      // Create a billboard collection with two billboards
      var billboards = scene.primitives.add(new Cesium.BillboardCollection());
      billboards.add({
        position : new Cesium.Cartesian3(1.0, 2.0, 3.0),
        image : 'url/to/image'
      });
      billboards.add({
        position : new Cesium.Cartesian3(4.0, 5.0, 6.0),
        image : 'url/to/another/image'
      });

  ##### Demo:

  - Cesium Sandcastle Billboard Demo

  ##### See:

  - BillboardCollection#add
  - BillboardCollection#remove
  - Billboard
  - LabelCollection

### Members

#### debugShowBoundingVolume : Boolean
Scene/BillboardCollection.js 256

  This property is for debugging only; it is not for production use nor is it optimized.

  Draws the bounding sphere for each draw command in the primitive.

  Default Value: `false`

#### length : Number
Scene/BillboardCollection.js 294

  Returns the number of billboards in this collection. This is commonly used with `BillboardCollection#get` to iterate over all the billboards in the collection.

#### modelMatrix : Matrix4
Scene/BillboardCollection.js 243

  The 4x4 transformation matrix that transforms each billboard in this collection from model to world coordinates. When this is the identity matrix, the billboards are drawn in world coordinates, i.e., Earth's WGS84 coordinates. Local reference frames can be used by providing a different transformation matrix, like that returned by `Transforms.eastNorthUpToFixedFrame`.
  Default Value: ``Matrix4.IDENTITY``

  ##### Example:

      var center = Cesium.Cartesian3.fromDegrees(-75.59777, 40.03883);
      billboards.modelMatrix = Cesium.Transforms.eastNorthUpToFixedFrame(center);
      billboards.add({
        image : 'url/to/image',
        position : new Cesium.Cartesian3(0.0, 0.0, 0.0) // center
      });
      billboards.add({
        image : 'url/to/image',
        position : new Cesium.Cartesian3(1000000.0, 0.0, 0.0) // east
      });
      billboards.add({
        image : 'url/to/image',
        position : new Cesium.Cartesian3(0.0, 1000000.0, 0.0) // north
      });
      billboards.add({
        image : 'url/to/image',
        position : new Cesium.Cartesian3(0.0, 0.0, 1000000.0) // up
      });

  ##### See:

  - Transforms.eastNorthUpToFixedFrame

### Methods

#### add(billboard) → Billboard
Scene/BillboardCollection.js 401

  Creates and adds a billboard with the specified initial properties to the collection. The added billboard is returned so it can be modified or removed from the collection later.

  ##### Performance:

  Calling `add` is expected constant time. However, the collection's vertex buffer is rewritten - an `O(n)` operation that also incurs CPU to GPU overhead. For best performance, add as many billboards as possible before calling `update`.

  Name | Type | Description
  --- | --- | ---
  `billboard` | Object | optional A template describing the billboard's properties as shown in Example 1.

  ##### Returns:

  The billboard that was added to the collection.

  ##### Throws:

  - DeveloperError : This object was destroyed, i.e., destroy() was called.

  ##### Examples:

      // Example 1:  Add a billboard, specifying all the default values.
      var b = billboards.add({
        show : true,
        position : Cesium.Cartesian3.ZERO,
        pixelOffset : Cesium.Cartesian2.ZERO,
        eyeOffset : Cesium.Cartesian3.ZERO,
        horizontalOrigin : Cesium.HorizontalOrigin.CENTER,
        verticalOrigin : Cesium.VerticalOrigin.CENTER,
        scale : 1.0,
        image : 'url/to/image',
        color : Cesium.Color.WHITE,
        id : undefined
      });

      // Example 2:  Specify only the billboard's cartographic position.
      var b = billboards.add({
        position : Cesium.Cartesian3.fromDegrees(longitude, latitude, height)
      });

  ##### See:

  - BillboardCollection#remove
  - BillboardCollection#removeAll

#### contains(billboard) → Boolean
Scene/BillboardCollection.js 508

  Check whether this collection contains a given billboard.

  Name | Type | Description
  --- | --- | ---
  `billboard` | Billboard | optional The billboard to check for.

  ##### Returns:

  true if this collection contains the billboard, false otherwise.

  ##### See:

  - BillboardCollection#get

#### destroy() → undefined
Scene/BillboardCollection.js 1562

  Destroys the WebGL resources held by this object. Destroying an object allows for deterministic release of WebGL resources, instead of relying on the garbage collector to destroy this object.
  Once an object is destroyed, it should not be used; calling any function other than `isDestroyed` will result in a `DeveloperError` exception. Therefore, assign the return value (`undefined`) to the object as done in the example.

  ##### Returns:

  ##### Throws:

  - DeveloperError : This object was destroyed, i.e., destroy() was called.

  ##### Example:

      billboards = billboards && billboards.destroy();

  ##### See:

  - BillboardCollection#isDestroyed

#### get(index) → Billboard
Scene/BillboardCollection.js 539

  Returns the billboard in the collection at the specified index. Indices are zero-based and increase as billboards are added. Removing a billboard shifts all billboards after it to the left, changing their indices. This function is commonly used with `BillboardCollection#length` to iterate over all the billboards in the collection.

  ##### Performance:

  Expected constant time. If billboards were removed from the collection and `BillboardCollection#update` was not called, an implicit `O(n)` operation is performed.

  Name | Type | Description
  --- | --- | ---
  `index` | Number | The zero-based index of the billboard.

  ##### Returns:

  The billboard at the specified index.

  ##### Throws:

  - DeveloperError : This object was destroyed, i.e., destroy() was called.

  ##### Example:

      // Toggle the show property of every billboard in the collection
      var len = billboards.length;
      for (var i = 0; i < len; ++i) {
        var b = billboards.get(i);
        b.show = !b.show;
      }

  ##### See:

  - BillboardCollection#length

#### isDestroyed() → Boolean
Scene/BillboardCollection.js 1540

  Returns true if this object was destroyed; otherwise, false.
  If this object was destroyed, it should not be used; calling any function other than `isDestroyed` will result in a `DeveloperError` exception.

  ##### Returns:

  `true` if this object was destroyed; otherwise, `false`.

  ##### See:

  - BillboardCollection#destroy

#### remove(billboard) → Boolean
Scene/BillboardCollection.js 434

  Removes a billboard from the collection.

  ##### Performance:

  Calling `remove` is expected constant time. However, the collection's vertex buffer is rewritten - an `O(n)` operation that also incurs CPU to GPU overhead. For best performance, remove as many billboards as possible before calling `update`. If you intend to temporarily hide a billboard, it is usually more efficient to call `Billboard#show` instead of removing and re-adding the billboard.

  Name | Type | Description
  --- | --- | ---
  `billboard` | Billboard | The billboard to remove.

  ##### Returns:

  `true` if the billboard was removed; `false` if the billboard was not found in the collection.

  ##### Throws:

  - DeveloperError : This object was destroyed, i.e., destroy() was called.

  ##### Example:

      var b = billboards.add(...);
      billboards.remove(b);  // Returns true

  ##### See:

  - BillboardCollection#add
  - BillboardCollection#removeAll
  - Billboard#show

#### removeAll()
Scene/BillboardCollection.js 463

  Removes all billboards from the collection.

  ##### Performance:

  `O(n)`. It is more efficient to remove all the billboards from a collection and then add new ones than to create a new collection entirely.

  ##### Throws:

  - DeveloperError : This object was destroyed, i.e., destroy() was called.

  ##### Example:

      billboards.add(...);
      billboards.add(...);
      billboards.removeAll();

  ##### See:

  - BillboardCollection#add
  - BillboardCollection#remove

#### update()
Scene/BillboardCollection.js 1170

  Called when `Viewer` or `CesiumWidget` render the scene to get the draw commands needed to render this primitive.

  Do not call this function directly. This is documented just to list the exceptions that may be propagated when the scene is rendered:

  ##### Throws:

  - RuntimeError : image with id must be in the atlas.