# Viewer

#### new Cesium.Viewer(container, options)
Widgets/Viewer/Viewer.js 364

A base widget for building applications. It composites all of the standard Cesium widgets into one reusable package. The widget can always be extended by using mixins, which add functionality useful for a variety of applications.

Name | Type | Description
--- | --- | ---
`container` | Element | String | The DOM element or ID that will contain the widget.

`options`

Object

optional Object with the following properties:

Name | Type | Default | Description
--- | --- | --- | ---
`animation` | Boolean | `true` | optional If set to false, the Animation widget will not be created.
`baseLayerPicker` | Boolean | `true` | optional If set to false, the BaseLayerPicker widget will not be created.
`fullscreenButton` | Boolean | `true` | optional If set to false, the FullscreenButton widget will not be created.
`vrButton` | Boolean | `false` | optional If set to true, the VRButton widget will be created.
`geocoder` | Boolean | Array.<GeocoderService> | `true` | optional If set to false, the Geocoder widget will not be created.
`homeButton` | Boolean | `true` | optional If set to false, the HomeButton widget will not be created.
`infoBox` | Boolean | `true` | optional If set to false, the InfoBox widget will not be created.
`sceneModePicker` | Boolean | `true` | optional If set to false, the SceneModePicker widget will not be created.
`selectionIndicator` | Boolean | `true` | optional If set to false, the SelectionIndicator widget will not be created.
`timeline` | Boolean | `true` | optional If set to false, the Timeline widget will not be created.
`navigationHelpButton` | Boolean | `true` | optional If set to false, the navigation help button will not be created.
`navigationInstructionsInitiallyVisible` | Boolean | `true` | optional True if the navigation instructions should initially be visible, or false if the should not be shown until the user explicitly clicks the button.
`scene3DOnly` | Boolean | `false` | optional When `true`, each geometry instance will only be rendered in 3D to save GPU memory.
`shouldAnimate` | Boolean | `false` | optional `true` if the clock should attempt to advance simulation time by default, `false` otherwise. This option takes precedence over setting `Viewer#clockViewModel`.
`clockViewModel` | ClockViewModel | `new ClockViewModel(options.clock)` | optional The clock view model to use to control current time.
`selectedImageryProviderViewModel` | ProviderViewModel |  | optional The view model for the current base imagery layer, if not supplied the first available base layer is used. This value is only valid if options.baseLayerPicker is set to true.
`imageryProviderViewModels` | Array.<ProviderViewModel> | `createDefaultImageryProviderViewModels()` | optional The array of ProviderViewModels to be selectable from the BaseLayerPicker. This value is only valid if options.baseLayerPicker is set to true.
`selectedTerrainProviderViewModel` | ProviderViewModel |  | optional The view model for the current base terrain layer, if not supplied the first available base layer is used. This value is only valid if options.baseLayerPicker is set to true.
`terrainProviderViewModels` | Array.<ProviderViewModel> | `createDefaultTerrainProviderViewModels()` | optional The array of ProviderViewModels to be selectable from the BaseLayerPicker. This value is only valid if options.baseLayerPicker is set to true.
`imageryProvider` | ImageryProvider | `createWorldImagery()` | optional The imagery provider to use. This value is only valid if options.baseLayerPicker is set to false.
`terrainProvider` | TerrainProvider | `new EllipsoidTerrainProvider()` | optional The terrain provider to use
`skyBox` | SkyBox |  | optional The skybox used to render the stars. When `undefined`, the default stars are used.
`skyAtmosphere` | SkyAtmosphere |  | optional Blue sky, and the glow around the Earth's limb. Set to `false` to turn it off.
`fullscreenElement` | Element | String | `document.body` | optional The element or id to be placed into fullscreen mode when the full screen button is pressed.
`useDefaultRenderLoop` | Boolean | `true` | optional True if this widget should control the render loop, false otherwise.
`targetFrameRate` | Number |  | optional The target frame rate when using the default render loop.
`showRenderLoopErrors` | Boolean | `true` | optional If true, this widget will automatically display an HTML panel to the user containing the error, if a render loop error occurs.
`automaticallyTrackDataSourceClocks` | Boolean | `true` | optional If true, this widget will automatically track the clock settings of newly added DataSources, updating if the DataSource's clock changes. Set this to false if you want to configure the clock independently.
`contextOptions` | Object |  | optional Context and WebGL creation properties corresponding to `options` passed to `Scene`.
`sceneMode` | SceneMode | `SceneMode.SCENE3D` | optional The initial scene mode.
`mapProjection` | MapProjection | `new GeographicProjection()` | optional The map projection to use in 2D and Columbus View modes.
`globe` | Globe | `new Globe(mapProjection.ellipsoid)` | optional The globe to use in the scene. If set to `false`, no globe will be added.
`orderIndependentTranslucency` | Boolean | `true` | optional If true and the configuration supports it, use order independent translucency.
`creditContainer` | Element | String |  | optional The DOM element or ID that will contain the `CreditDisplay`. If not specified, the credits are added to the bottom of the widget itself.
`creditViewport` | Element | String |  | optional The DOM element or ID that will contain the credit pop up created by the `CreditDisplay`. If not specified, it will appear over the widget itself.
`dataSources` | DataSourceCollection | `new DataSourceCollection()` | optional The collection of data sources visualized by the widget. If this parameter is provided, the instance is assumed to be owned by the caller and will not be destroyed when the viewer is destroyed.
`terrainExaggeration` | Number | `1.0` | optional A scalar used to exaggerate the terrain. Note that terrain exaggeration will not modify any other primitive as they are positioned relative to the ellipsoid.
`terrainShowSkirt` | Boolean | `true` | optional 是否显示裙边
`shadows` | Boolean | `false` | optional Determines if shadows are cast by the sun.
`terrainShadows` | ShadowMode | `ShadowMode.RECEIVE_ONLY` | optional Determines if the terrain casts or receives shadows from the sun.
`mapMode2D` | MapMode2D | `MapMode2D.INFINITE_SCROLL` | optional Determines if the 2D map is rotatable or can be scrolled infinitely in the horizontal direction.
`projectionPicker` | Boolean | `false` | optional If set to true, the ProjectionPicker widget will be created.

`requestRenderMode`

Boolean

`false`

optional If true, rendering a frame will only occur when needed as determined by changes within the scene. Enabling improves performance of the application, but requires using `Scene#requestRender` to render a new frame explicitly in this mode. This will be necessary in many cases after making changes to the scene in other parts of the API. See Improving Performance with Explicit Rendering.

`maximumRenderTimeChange` | Number | `0.0` | optional If requestRenderMode is true, this value defines the maximum change in simulation time allowed before a render is requested. See Improving Performance with Explicit Rendering.

##### Throws:

- DeveloperError : Element with id "container" does not exist in the document.
- DeveloperError : options.selectedImageryProviderViewModel is not available when not using the BaseLayerPicker widget, specify options.imageryProvider instead.
- DeveloperError : options.selectedTerrainProviderViewModel is not available when not using the BaseLayerPicker widget, specify options.terrainProvider instead.

##### Example:

    //Initialize the viewer widget with several custom options and mixins.
    var viewer = new Cesium.Viewer('cesiumContainer', {
        //Start in Columbus Viewer
        sceneMode : Cesium.SceneMode.COLUMBUS_VIEW,
        //Use Cesium World Terrain
        terrainProvider : Cesium.createWorldTerrain(),
        //Hide the base layer picker
        baseLayerPicker : false,
        //Use OpenStreetMaps
        imageryProvider : Cesium.createOpenStreetMapImageryProvider({
            url : 'https://a.tile.openstreetmap.org/'
        }),
        // Use high-res stars downloaded from https://github.com/AnalyticalGraphicsInc/cesium-assets
        skyBox : new Cesium.SkyBox({
            sources : {
              positiveX : 'stars/TychoSkymapII.t3_08192x04096_80_px.jpg',
              negativeX : 'stars/TychoSkymapII.t3_08192x04096_80_mx.jpg',
              positiveY : 'stars/TychoSkymapII.t3_08192x04096_80_py.jpg',
              negativeY : 'stars/TychoSkymapII.t3_08192x04096_80_my.jpg',
              positiveZ : 'stars/TychoSkymapII.t3_08192x04096_80_pz.jpg',
              negativeZ : 'stars/TychoSkymapII.t3_08192x04096_80_mz.jpg'
            }
        }),
        // Show Columbus View map with Web Mercator projection
        mapProjection : new Cesium.WebMercatorProjection()
    });

    //Add basic drag and drop functionality
    viewer.extend(Cesium.viewerDragDropMixin);

    //Show a pop-up alert if we encounter an error when processing a dropped file
    viewer.dropError.addEventListener(function(dropHandler, name, error) {
        console.log(error);
        window.alert(error);
    });

##### Demo:

- Cesium Sandcastle Hello World Demo

##### See:

- Animation
- BaseLayerPicker
- CesiumWidget
- FullscreenButton
- HomeButton
- SceneModePicker
- Timeline
- viewerDragDropMixin

### Members

#### allowDataSourcesToSuspendAnimation : Boolean
Widgets/Viewer/Viewer.js 1276

Gets or sets whether or not data sources can temporarily pause animation in order to avoid showing an incomplete picture to the user. For example, if asynchronous primitives are being processed in the background, the clock will not advance until the geometry is ready.

#### readonlyanimation : Animation
Widgets/Viewer/Viewer.js 970

Gets the Animation widget.

#### readonlybaseLayerPicker : BaseLayerPicker
Widgets/Viewer/Viewer.js 946

Gets the BaseLayerPicker.

#### readonlybottomContainer : Element
Widgets/Viewer/Viewer.js 850

Gets the DOM element for the area at the bottom of the window containing the `CreditDisplay` and potentially other things.

#### readonlycamera : Camera
Widgets/Viewer/Viewer.js 1148

Gets the camera.

#### readonlycanvas : Canvas
Widgets/Viewer/Viewer.js 1055

Gets the canvas.

#### readonlycesiumWidget : CesiumWidget
Widgets/Viewer/Viewer.js 862

Gets the CesiumWidget.

#### readonlyclock : Clock
Widgets/Viewer/Viewer.js 1173

Gets the clock.

#### clockTrackedDataSource : DataSource
Widgets/Viewer/Viewer.js 1380

Gets or sets the data source to track with the viewer's clock.

#### readonlyclockViewModel : ClockViewModel
Widgets/Viewer/Viewer.js 1185

Gets the clock view model.

#### readonlycontainer : Element
Widgets/Viewer/Viewer.js 837

Gets the parent container.

#### readonlydataSourceDisplay : DataSourceDisplay
Widgets/Viewer/Viewer.js 1018

Gets the display used for `DataSource` visualization.

#### readonlydataSources : DataSourceCollection
Widgets/Viewer/Viewer.js 1043

Gets the set of `DataSource` instances to be visualized.

#### readonlyentities : EntityCollection
Widgets/Viewer/Viewer.js 1031

Gets the collection of entities not tied to a particular data source. This is a shortcut to `dataSourceDisplay.defaultDataSource.entities`.

#### readonlyfullscreenButton : FullscreenButton
Widgets/Viewer/Viewer.js 994

Gets the FullscreenButton.

#### readonlygeocoder : Geocoder
Widgets/Viewer/Viewer.js 898

Gets the Geocoder.

#### readonlyhomeButton : HomeButton
Widgets/Viewer/Viewer.js 910

Gets the HomeButton.

#### readonlyimageryLayers : ImageryLayerCollection
Widgets/Viewer/Viewer.js 1120

Gets the collection of image layers that will be rendered on the globe.

#### readonlyinfoBox : InfoBox
Widgets/Viewer/Viewer.js 886

Gets the info box.

#### readonlynavigationHelpButton : NavigationHelpButton
Widgets/Viewer/Viewer.js 958

Gets the NavigationHelpButton.

#### readonlypostProcessStages : PostProcessStageCollection
Widgets/Viewer/Viewer.js 1161

Gets the post-process stages.

#### readonlyprojectionPicker : ProjectionPicker
Widgets/Viewer/Viewer.js 934

Gets the ProjectionPicker.

#### resolutionScale : Number
Widgets/Viewer/Viewer.js 1256

Gets or sets a scaling factor for rendering resolution. Values less than 1.0 can improve performance on less powerful devices while values greater than 1.0 will render at a higher resolution and then scale down, resulting in improved visual fidelity. For example, if the widget is laid out at a size of 640x480, setting this value to 0.5 will cause the scene to be rendered at 320x240 and then scaled up while setting it to 2.0 will cause the scene to be rendered at 1280x960 and then scaled down.

Default Value: `1.0`

#### readonlyscene : Scene
Widgets/Viewer/Viewer.js 1067

Gets the scene.

#### readonlysceneModePicker : SceneModePicker
Widgets/Viewer/Viewer.js 922

Gets the SceneModePicker.

#### readonlyscreenSpaceEventHandler : ScreenSpaceEventHandler
Widgets/Viewer/Viewer.js 1197

Gets the screen space event handler.

#### selectedEntity : Entity
Widgets/Viewer/Viewer.js 1333

Gets or sets the object instance for which to display a selection indicator.

#### readonlyselectedEntityChanged : Event
Widgets/Viewer/Viewer.js 1359

Gets the event that is raised when the selected entity changes.

#### readonlyselectionIndicator : SelectionIndicator
Widgets/Viewer/Viewer.js 874

Gets the selection indicator.

#### readonlyshadowMap : ShadowMap
Widgets/Viewer/Viewer.js 1107

Get the scene's shadow map

#### shadows : Boolean
Widgets/Viewer/Viewer.js 1078

Determines if shadows are cast by the sun.

#### targetFrameRate : Number
Widgets/Viewer/Viewer.js 1212

Gets or sets the target frame rate of the widget when `useDefaultRenderLoop` is true. If undefined, the browser's `requestAnimationFrame` implementation determines the frame rate. If defined, this value must be greater than 0. A value higher than the underlying requestAnimationFrame implementation will have no effect.

#### terrainProvider : TerrainProvider
Widgets/Viewer/Viewer.js 1132

The terrain provider providing surface geometry for the globe.

#### terrainShadows : ShadowMode
Widgets/Viewer/Viewer.js 1092

Determines if the terrain casts or shadows from the sun.

#### readonlytimeline : Timeline
Widgets/Viewer/Viewer.js 982

Gets the Timeline widget.

#### trackedEntity : Entity
Widgets/Viewer/Viewer.js 1290

Gets or sets the Entity instance currently being tracked by the camera.

#### readonlytrackedEntityChanged : Event
Widgets/Viewer/Viewer.js 1370

Gets the event that is raised when the tracked entity changes.

#### useDefaultRenderLoop : Boolean
Widgets/Viewer/Viewer.js 1235

Gets or sets whether or not this widget should control the render loop. If set to true the widget will use `requestAnimationFrame` to perform rendering and resizing of the widget, as well as drive the simulation clock. If set to false, you must manually call the `resize`, `render` methods as part of a custom render loop. If an error occurs during rendering, `Scene`'s `renderError` event will be raised and this property will be set to false. It must be set back to true to continue rendering after the error.

#### readonlyvrButton : VRButton
Widgets/Viewer/Viewer.js 1006

Gets the VRButton.

### Methods

#### destroy()
Widgets/Viewer/Viewer.js 1538

Destroys the widget. Should be called if permanently removing the widget from layout.

#### extend(mixin, options)
Widgets/Viewer/Viewer.js 1403

Extends the base viewer functionality with the provided mixin. A mixin may add additional properties, functions, or other behavior to the provided viewer instance.

Name | Type | Description
--- | --- | ---
`mixin` | Viewer~ViewerMixin | The Viewer mixin to add to this instance.
`options` | Object | optional The options object to be passed to the mixin function.

##### See:

- viewerDragDropMixin

#### flyTo(target, options) → Promise.<Boolean>
Widgets/Viewer/Viewer.js 1869

Flies the camera to the provided entity, entities, or data source. If the data source is still in the process of loading or the visualization is otherwise still loading, this method waits for the data to be ready before performing the flight.

The offset is heading/pitch/range in the local east-north-up reference frame centered at the center of the bounding sphere. The heading and the pitch angles are defined in the local east-north-up reference frame. The heading is the angle from y axis and increasing towards the x axis. Pitch is the rotation from the xy-plane. Positive pitch angles are above the plane. Negative pitch angles are below the plane. The range is the distance from the center. If the range is zero, a range will be computed such that the whole bounding sphere is visible.

In 2D, there must be a top down view. The camera will be placed above the target looking down. The height above the target will be the range. The heading will be determined from the offset. If the heading cannot be determined from the offset, the heading will be north.

Name | Type | Description
--- | --- | ---

`target`

Entity | Array.<Entity> | EntityCollection | DataSource | ImageryLayer | Cesium3DTileset | TimeDynamicPointCloud | Promise.<(Entity|Array.<Entity>|EntityCollection|DataSource|ImageryLayer|Cesium3DTileset|TimeDynamicPointCloud)>

The entity, array of entities, entity collection, data source, Cesium3DTileset, point cloud, or imagery layer to view. You can also pass a promise that resolves to one of the previously mentioned types.

`options`

Object

optional Object with the following properties:

Name | Type | Default | Description
--- | --- | --- | ---
`duration` | Number | `3.0` | optional The duration of the flight in seconds.
`maximumHeight` | Number |  | optional The maximum height at the peak of the flight.
`offset` | HeadingPitchRange |  | optional The offset from the target in the local east-north-up reference frame centered at the target.

##### Returns:

A Promise that resolves to true if the flight was successful or false if the target is not currently visualized in the scene or the flight was cancelled. //TODO: Cleanup entity mentions

#### forceResize()
Widgets/Viewer/Viewer.js 1514

This forces the widget to re-think its layout, including widget sizes and credit placement.

#### getCartesian3Position(screePosition, position) → Cartesian3
Widgets/Viewer/Viewer.js 1990

根据 场景模式得到拾取坐标

Name | Type | Description
--- | --- | ---
`screePosition` | Cartesian2 | 屏幕坐标
`position` | Cartesian3 | 返回的世界坐标

##### Returns:

返回的世界坐标 (注意检查返回值是否为undefined 因为拾取在天空背景上是undefined)

Author:
  - hys

#### isDestroyed() → Boolean
Widgets/Viewer/Viewer.js 1530

##### Returns:

true if the object has been destroyed, false otherwise.

#### render()
Widgets/Viewer/Viewer.js 1523

Renders the scene. This function is called automatically unless `useDefaultRenderLoop` is set to false;

#### resize()
Widgets/Viewer/Viewer.js 1418

Resizes the widget to match the container size. This function is called automatically as needed unless `useDefaultRenderLoop` is set to false.

#### zoomTo(target, offset) → Promise.<Boolean>
Widgets/Viewer/Viewer.js 1840

Asynchronously sets the camera to view the provided entity, entities, or data source. If the data source is still in the process of loading or the visualization is otherwise still loading, this method waits for the data to be ready before performing the zoom.

The offset is heading/pitch/range in the local east-north-up reference frame centered at the center of the bounding sphere. The heading and the pitch angles are defined in the local east-north-up reference frame. The heading is the angle from y axis and increasing towards the x axis. Pitch is the rotation from the xy-plane. Positive pitch angles are above the plane. Negative pitch angles are below the plane. The range is the distance from the center. If the range is zero, a range will be computed such that the whole bounding sphere is visible.

In 2D, there must be a top down view. The camera will be placed above the target looking down. The height above the target will be the range. The heading will be determined from the offset. If the heading cannot be determined from the offset, the heading will be north.

Name | Type | Description
--- | --- | ---

`target`

Entity | Array.<Entity> | EntityCollection | DataSource | ImageryLayer | Cesium3DTileset | TimeDynamicPointCloud | Promise.<(Entity|Array.<Entity>|EntityCollection|DataSource|ImageryLayer|Cesium3DTileset|TimeDynamicPointCloud)>

The entity, array of entities, entity collection, data source, Cesium3DTileset, point cloud, or imagery layer to view. You can also pass a promise that resolves to one of the previously mentioned types.

`offset` | HeadingPitchRange | optional The offset from the center of the entity in the local east-north-up reference frame.

##### Returns:

A Promise that resolves to true if the zoom was successful or false if the target is not currently visualized in the scene or the zoom was cancelled.

### Type Definitions

#### ViewerMixin(viewer, options)
Widgets/Viewer/Viewer.js 2223

A function that augments a Viewer instance with additional functionality.

Name | Type | Description
--- | --- | ---
`viewer` | Viewer | The viewer instance.
`options` | Object | Options object to be passed to the mixin function.

##### See:

- Viewer#extend