ClassificationPrimitive — Cesium API reference

new Cesium.ClassificationPrimitive(options)

A classification primitive represents a volume enclosing geometry in the Scene to be highlighted.

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. Only PerInstanceColorAppearance with the same color across all instances is supported at this time when using ClassificationPrimitive directly. For full Appearance support when classifying terrain or 3D Tiles use GroundPrimitive instead.

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 BoxGeometry, CylinderGeometry, EllipsoidGeometry, PolylineVolumeGeometry, and SphereGeometry.

Geometries that follow the surface of the ellipsoid, such as CircleGeometry, CorridorGeometry, EllipseGeometry, PolygonGeometry, and RectangleGeometry, are also valid if they are extruded volumes; otherwise, they will not be rendered.

Name Type Description

options

object

optional Object with the following properties:

Name	Type	Default	Description
`geometryInstances`	Array \| GeometryInstance		optional The geometry instances to render. This can either be a single instance or an array of length one.
`appearance`	Appearance		optional The appearance used to render the primitive. Defaults to 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`.

See:

Primitive
GroundPrimitive
GeometryInstance
Appearance

Members

readonly allowPicking : boolean

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

Default Value: true

readonly asynchronous : boolean

Determines if the geometry instances will be created and batched on a web worker.

Default Value: true

classificationType : ClassificationType

Determines whether terrain, 3D Tiles or both will be classified.

Default Value: ClassificationType.BOTH

readonly compressVertices : boolean

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

Default Value: true

debugShowBoundingVolume : boolean

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

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

The geometry instance 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.

Because of the rendering technique used, all geometry instances must be the same color. If there is an instance with a differing color, a DeveloperError will be thrown on the first attempt to render.

Default Value: undefined

readonly interleave : boolean

Determines if geometry vertex attributes are interleaved, which can slightly improve rendering performance.

Default Value: false

readonly ready : boolean

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

readonly releaseGeometryInstances : boolean

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

Default Value: true

show : boolean

Determines if the primitive will be shown. This affects all geometry instances in the primitive.

Default Value: true

readonly vertexCacheOptimize : boolean

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

Default Value: true

Methods

static Cesium.ClassificationPrimitive.isSupported(scene) → boolean

Determines if ClassificationPrimitive rendering is supported.

Name	Type	Description
`scene`	Scene	The scene.

Returns:

true if ClassificationPrimitives are supported; otherwise, returns false

destroy()

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:

ClassificationPrimitive#isDestroyed

getGeometryInstanceAttributes(id) → object

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

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:

ClassificationPrimitive#destroy

update()

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 : All instance geometries must have the same primitiveType.
DeveloperError : Appearance and material have a uniform with the same name.
DeveloperError : Not all of the geometry instances have the same color attribute.