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GroundPrimitive

new Cesium.GroundPrimitive(options)
engine/Source/Scene/GroundPrimitive.js 114

A ground primitive represents geometry draped over terrain or 3D Tiles in the Scene.

A primitive combines geometry instances with an Appearance that describes the full shading, including Material and RenderState. Roughly, the geometry instance defines the structure and placement, and the appearance defines the visual characteristics. Decoupling geometry and appearance allows us to mix and match most of them and add a new geometry or appearance independently of each other.

Support for the WEBGL_depth_texture extension is required to use GeometryInstances with different PerInstanceColors or materials besides PerInstanceColorAppearance.

Textured GroundPrimitives were designed for notional patterns and are not meant for precisely mapping textures to terrain - for that use case, use SingleTileImageryProvider.

For correct rendering, this feature requires the EXT_frag_depth WebGL extension. For hardware that do not support this extension, there will be rendering artifacts for some viewing angles.

Valid geometries are CircleGeometry, CorridorGeometry, EllipseGeometry, PolygonGeometry, and RectangleGeometry.

Name Type Description
options object optional Object with the following properties:
Name Type Default Description
geometryInstances Array | GeometryInstance optional The geometry instances to render.
appearance Appearance optional The appearance used to render the primitive. Defaults to a flat PerInstanceColorAppearance when GeometryInstances have a color attribute.
show boolean true optional Determines if this primitive will be shown.
vertexCacheOptimize boolean false optional When true, geometry vertices are optimized for the pre and post-vertex-shader caches.
interleave boolean false optional When true, geometry vertex attributes are interleaved, which can slightly improve rendering performance but increases load time.
compressVertices boolean true optional When true, the geometry vertices are compressed, which will save memory.
releaseGeometryInstances boolean true optional When true, the primitive does not keep a reference to the input geometryInstances to save memory.
allowPicking boolean true optional When true, each geometry instance will only be pickable with Scene#pick. When false, GPU memory is saved.
asynchronous boolean true optional Determines if the primitive will be created asynchronously or block until ready. If false initializeTerrainHeights() must be called first.
classificationType ClassificationType ClassificationType.BOTH optional Determines whether terrain, 3D Tiles or both will be classified.
debugShowBoundingVolume boolean false optional For debugging only. Determines if this primitive's commands' bounding spheres are shown.
debugShowShadowVolume boolean false optional For debugging only. Determines if the shadow volume for each geometry in the primitive is drawn. Must be true on creation for the volumes to be created before the geometry is released or options.releaseGeometryInstance must be false.
Example:
// Example 1: Create primitive with a single instance
const rectangleInstance = new Cesium.GeometryInstance({
  geometry : new Cesium.RectangleGeometry({
    rectangle : Cesium.Rectangle.fromDegrees(-140.0, 30.0, -100.0, 40.0)
  }),
  id : 'rectangle',
  attributes : {
    color : new Cesium.ColorGeometryInstanceAttribute(0.0, 1.0, 1.0, 0.5)
  }
});
scene.primitives.add(new Cesium.GroundPrimitive({
  geometryInstances : rectangleInstance
}));

// Example 2: Batch instances
const color = new Cesium.ColorGeometryInstanceAttribute(0.0, 1.0, 1.0, 0.5); // Both instances must have the same color.
const rectangleInstance = new Cesium.GeometryInstance({
  geometry : new Cesium.RectangleGeometry({
    rectangle : Cesium.Rectangle.fromDegrees(-140.0, 30.0, -100.0, 40.0)
  }),
  id : 'rectangle',
  attributes : {
    color : color
  }
});
const ellipseInstance = new Cesium.GeometryInstance({
    geometry : new Cesium.EllipseGeometry({
        center : Cesium.Cartesian3.fromDegrees(-105.0, 40.0),
        semiMinorAxis : 300000.0,
        semiMajorAxis : 400000.0
    }),
    id : 'ellipse',
    attributes : {
        color : color
    }
});
scene.primitives.add(new Cesium.GroundPrimitive({
  geometryInstances : [rectangleInstance, ellipseInstance]
}));
See:

Members

readonly allowPicking : boolean
engine/Source/Scene/GroundPrimitive.js 309

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

appearance : Appearance
engine/Source/Scene/GroundPrimitive.js 144

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

readonly asynchronous : boolean
engine/Source/Scene/GroundPrimitive.js 325

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

classificationType : ClassificationType
engine/Source/Scene/GroundPrimitive.js 176

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

readonly compressVertices : boolean
engine/Source/Scene/GroundPrimitive.js 341

When true, geometry vertices are compressed, which will save memory.
Default Value: true

debugShowBoundingVolume : boolean
engine/Source/Scene/GroundPrimitive.js 190

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

debugShowShadowVolume : boolean
engine/Source/Scene/GroundPrimitive.js 205

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

Draws the shadow volume for each geometry in the primitive.

Default Value: false

readonly geometryInstances : Array|GeometryInstance
engine/Source/Scene/GroundPrimitive.js 159

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.

Default Value: undefined

readonly interleave : boolean
engine/Source/Scene/GroundPrimitive.js 277

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

readonly ready : boolean
engine/Source/Scene/GroundPrimitive.js 357

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

readonly releaseGeometryInstances : boolean
engine/Source/Scene/GroundPrimitive.js 293

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

show : boolean
engine/Source/Scene/GroundPrimitive.js 168

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

readonly vertexCacheOptimize : boolean
engine/Source/Scene/GroundPrimitive.js 261

When true, geometry vertices are optimized for the pre and post-vertex-shader caches.
Default Value: true

Methods

static Cesium.GroundPrimitive.initializeTerrainHeights() → Promise.<void>
engine/Source/Scene/GroundPrimitive.js 682

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

static Cesium.GroundPrimitive.isSupported(scene) → boolean
engine/Source/Scene/GroundPrimitive.js 371

Determines if GroundPrimitive rendering is supported.
Name Type Description
scene Scene The scene.
Returns:
true if GroundPrimitives are supported; otherwise, returns false

static Cesium.GroundPrimitive.supportsMaterials(scene) → boolean
engine/Source/Scene/GroundPrimitive.js 1002

Checks if the given Scene supports materials on GroundPrimitives. Materials on GroundPrimitives require support for the WEBGL_depth_texture extension.
Name Type Description
scene Scene The current scene.
Returns:
Whether or not the current scene supports materials on GroundPrimitives.

destroy()
engine/Source/Scene/GroundPrimitive.js 979

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.
Example:
e = e && e.destroy();
See:

getGeometryInstanceAttributes(id) → object
engine/Source/Scene/GroundPrimitive.js 937

Returns the modifiable per-instance attributes for a GeometryInstance.
Name Type Description
id * The id of the GeometryInstance.
Returns:
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.
Example:
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/GroundPrimitive.js 959

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:

update()
engine/Source/Scene/GroundPrimitive.js 698

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 GroundPrimitive, you must call GroundPrimitive.initializeTerrainHeights() and wait for the returned promise to resolve.
  • DeveloperError : All instance geometries must have the same primitiveType.
  • DeveloperError : Appearance and material have a uniform with the same name.
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