GroundPolylinePrimitive
查阅Mars3D API

new Cesium.GroundPolylinePrimitive(options)
engine/Source/Scene/GroundPolylinePrimitive.js 96

A GroundPolylinePrimitive represents a polyline draped over the terrain or 3D Tiles in the Scene.

Only to be used with GeometryInstances containing GroundPolylineGeometry.

参数名称 类型 描述信息
options object 可选 Object with the following properties:
参数名称 类型 默认值 描述信息
geometryInstances Array | GeometryInstance 可选 GeometryInstances containing GroundPolylineGeometry
appearance Appearance 可选 The Appearance used to render the polyline. Defaults to a white color Material on a PolylineMaterialAppearance.
show boolean true 可选 Determines if this primitive will be shown.
interleave boolean false 可选 When true, geometry vertex attributes are interleaved, which can slightly improve rendering performance but increases load time.
releaseGeometryInstances boolean true 可选 When true, the primitive does not keep a reference to the input geometryInstances to save memory.
allowPicking boolean true 可选 When true, each geometry instance will only be pickable with Scene#pick. When false, GPU memory is saved.
asynchronous boolean true 可选 Determines if the primitive will be created asynchronously or block until ready. If false initializeTerrainHeights() must be called first.
classificationType ClassificationType ClassificationType.BOTH 可选 Determines whether terrain, 3D Tiles or both will be classified.
debugShowBoundingVolume boolean false 可选 For debugging only. Determines if this primitive's commands' bounding spheres are shown.
debugShowShadowVolume boolean false 可选 For debugging only. Determines if the shadow volume for each geometry in the primitive is drawn. Must be true on creation to have effect.
使用示例:
// 1. Draw a polyline on terrain with a basic color material

const instance = new Cesium.GeometryInstance({
  geometry : new Cesium.GroundPolylineGeometry({
     positions : Cesium.Cartesian3.fromDegreesArray([
         -112.1340164450331, 36.05494287836128,
         -112.08821010582645, 36.097804071380715
     ]),
     width : 4.0
  }),
  id : 'object returned when this instance is picked and to get/set per-instance attributes'
});

scene.groundPrimitives.add(new Cesium.GroundPolylinePrimitive({
  geometryInstances : instance,
  appearance : new Cesium.PolylineMaterialAppearance()
}));

// 2. Draw a looped polyline on terrain with per-instance color and a distance display condition.
// Distance display conditions for polylines on terrain are based on an approximate terrain height
// instead of true terrain height.

const instance2 = new Cesium.GeometryInstance({
  geometry : new Cesium.GroundPolylineGeometry({
     positions : Cesium.Cartesian3.fromDegreesArray([
         -112.1340164450331, 36.05494287836128,
         -112.08821010582645, 36.097804071380715,
         -112.13296079730024, 36.168769146801104
     ]),
     loop : true,
     width : 4.0
  }),
  attributes : {
     color : Cesium.ColorGeometryInstanceAttribute.fromColor(Cesium.Color.fromCssColorString('green').withAlpha(0.7)),
     distanceDisplayCondition : new Cesium.DistanceDisplayConditionGeometryInstanceAttribute(1000, 30000)
  },
  id : 'object returned when this instance is picked and to get/set per-instance attributes'
});

scene.groundPrimitives.add(new Cesium.GroundPolylinePrimitive({
  geometryInstances : instance2,
  appearance : new Cesium.PolylineColorAppearance()
}));

成员(属性)

readonly allowPicking : boolean
engine/Source/Scene/GroundPolylinePrimitive.js 260

When true, each geometry instance will only be pickable with Scene#pick. When false, GPU memory is saved.
默认值: true

appearance : Appearance
engine/Source/Scene/GroundPolylinePrimitive.js 129

The Appearance used to shade this primitive. Each geometry instance is shaded with the same appearance. Some appearances, like PolylineColorAppearance allow giving each instance unique properties.
默认值: undefined

readonly asynchronous : boolean
engine/Source/Scene/GroundPolylinePrimitive.js 276

Determines if the geometry instances will be created and batched on a web worker.
默认值: true

classificationType : ClassificationType
engine/Source/Scene/GroundPolylinePrimitive.js 148

Determines whether terrain, 3D Tiles or both will be classified.
默认值: ClassificationType.BOTH

debugShowBoundingVolume : boolean
engine/Source/Scene/GroundPolylinePrimitive.js 163

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.

默认值: false

readonly debugShowShadowVolume : boolean
engine/Source/Scene/GroundPolylinePrimitive.js 311

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

If true, draws the shadow volume for each geometry in the primitive.

默认值: false

readonly geometryInstances : Array|GeometryInstance
engine/Source/Scene/GroundPolylinePrimitive.js 112

The geometry instances rendered with this primitive. This may be undefined if options.releaseGeometryInstances is true when the primitive is constructed.

Changing this property after the primitive is rendered has no effect.

默认值: undefined

readonly interleave : boolean
engine/Source/Scene/GroundPolylinePrimitive.js 228

Determines if geometry vertex attributes are interleaved, which can slightly improve rendering performance.
默认值: false

readonly ready : boolean
engine/Source/Scene/GroundPolylinePrimitive.js 292

Determines if the primitive is complete and ready to render. If this property is true, the primitive will be rendered the next time that GroundPolylinePrimitive#update is called.

readonly releaseGeometryInstances : boolean
engine/Source/Scene/GroundPolylinePrimitive.js 244

When true, the primitive does not keep a reference to the input geometryInstances to save memory.
默认值: true

show : boolean
engine/Source/Scene/GroundPolylinePrimitive.js 139

Determines if the primitive will be shown. This affects all geometry instances in the primitive.
默认值: true

方法

static Cesium.GroundPolylinePrimitive.initializeTerrainHeights() → Promise.<void>
engine/Source/Scene/GroundPolylinePrimitive.js 324

Initializes the minimum and maximum terrain heights. This only needs to be called if you are creating the GroundPolylinePrimitive synchronously.
返回值:
A promise that will resolve once the terrain heights have been loaded.

static Cesium.GroundPolylinePrimitive.isSupported(scene) → boolean
engine/Source/Scene/GroundPolylinePrimitive.js 856

Checks if the given Scene supports GroundPolylinePrimitives. GroundPolylinePrimitives require support for the WEBGL_depth_texture extension.
参数名称 类型 描述信息
scene Scene The current scene.
返回值:
Whether or not the current scene supports GroundPolylinePrimitives.

destroy()
engine/Source/Scene/GroundPolylinePrimitive.js 891

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.

Throws:
  • DeveloperError : This object was destroyed, i.e., destroy() was called.
使用示例:
e = e && e.destroy();
参考:

getGeometryInstanceAttributes(id) → object
engine/Source/Scene/GroundPolylinePrimitive.js 836

Returns the modifiable per-instance attributes for a GeometryInstance.
参数名称 类型 描述信息
id * The id of the GeometryInstance.
返回值:
The typed array in the attribute's format or undefined if the is no instance with id.
Throws:
  • DeveloperError : must call update before calling getGeometryInstanceAttributes.
使用示例:
const attributes = primitive.getGeometryInstanceAttributes('an id');
attributes.color = Cesium.ColorGeometryInstanceAttribute.toValue(Cesium.Color.AQUA);
attributes.show = Cesium.ShowGeometryInstanceAttribute.toValue(true);

isDestroyed() → boolean
engine/Source/Scene/GroundPolylinePrimitive.js 871

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.

返回值:
true if this object was destroyed; otherwise, false.
参考:

update()
engine/Source/Scene/GroundPolylinePrimitive.js 673

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:
  • DeveloperError : For synchronous GroundPolylinePrimitives, you must call GroundPolylinePrimitives.initializeTerrainHeights() and wait for the returned promise to resolve.
  • DeveloperError : All GeometryInstances must have color attributes to use PolylineColorAppearance with GroundPolylinePrimitive.
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