GroundPrimitive

new Cesium.GroundPrimitive(options)
Scene/GroundPrimitive.js 157

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
var 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
var color = new Cesium.ColorGeometryInstanceAttribute(0.0, 1.0, 1.0, 0.5); // Both instances must have the same color.
var 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
  }
});
var 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

readonlyallowPicking : Boolean
Scene/GroundPrimitive.js 340

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

appearance : Appearance
Scene/GroundPrimitive.js 185

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

readonlyasynchronous : Boolean
Scene/GroundPrimitive.js 356

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

classificationType : ClassificationType
Scene/GroundPrimitive.js 217

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

readonlycompressVertices : Boolean
Scene/GroundPrimitive.js 372

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

debugShowBoundingVolume : Boolean
Scene/GroundPrimitive.js 228

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
Scene/GroundPrimitive.js 240

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

readonlygeometryInstances : Array|GeometryInstance
Scene/GroundPrimitive.js 200

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

readonlyinterleave : Boolean
Scene/GroundPrimitive.js 308

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

readonlyready : Boolean
Scene/GroundPrimitive.js 388

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.

readonlyreadyPromise : Promise.<GroundPrimitive>
Scene/GroundPrimitive.js 400

Gets a promise that resolves when the primitive is ready to render.

readonlyreleaseGeometryInstances : Boolean
Scene/GroundPrimitive.js 324

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

show : Boolean
Scene/GroundPrimitive.js 209

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

readonlyvertexCacheOptimize : Boolean
Scene/GroundPrimitive.js 292

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

Methods

staticCesium.GroundPrimitive.initializeTerrainHeights() → Promise
Scene/GroundPrimitive.js 628

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.

staticCesium.GroundPrimitive.isSupported(scene) → Boolean
Scene/GroundPrimitive.js 414

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

staticCesium.GroundPrimitive.supportsMaterials(scene) → Boolean
Scene/GroundPrimitive.js 890

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()
Scene/GroundPrimitive.js 867

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
Scene/GroundPrimitive.js 827

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:
var attributes = primitive.getGeometryInstanceAttributes('an id');
attributes.color = Cesium.ColorGeometryInstanceAttribute.toValue(Cesium.Color.AQUA);
attributes.show = Cesium.ShowGeometryInstanceAttribute.toValue(true);

isDestroyed() → Boolean
Scene/GroundPrimitive.js 847

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()
Scene/GroundPrimitive.js 644

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.