Primitive

new Cesium.Primitive(options)

A primitive represents geometry in the Scene. The geometry can be from a single GeometryInstance as shown in example 1 below, or from an array of instances, even if the geometry is from different geometry types, e.g., an RectangleGeometry and an EllipsoidGeometry as shown in Code Example 2.

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.

Combining multiple instances into one primitive is called batching, and significantly improves performance for static data. Instances can be individually picked; Scene#pick returns their GeometryInstance#id. Using per-instance appearances like PerInstanceColorAppearance, each instance can also have a unique color.

Geometry can either be created and batched on a web worker or the main thread. The first two examples show geometry that will be created on a web worker by using the descriptions of the geometry. The third example shows how to create the geometry on the main thread by explicitly calling the createGeometry method.

Name Type Description
options Object optional Object with the following properties:
Name Type Default Description
geometryInstances Array.<GeometryInstance> | GeometryInstance optional The geometry instances - or a single geometry instance - to render.
appearance Appearance optional The appearance used to render the primitive.
show Boolean true optional Determines if this primitive will be shown.
modelMatrix Matrix4 Matrix4.IDENTITY optional The 4x4 transformation matrix that transforms the primitive (all geometry instances) from model to world coordinates.
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.
cull Boolean true optional When true, the renderer frustum culls and horizon culls the primitive's commands based on their bounding volume. Set this to false for a small performance gain if you are manually culling the primitive.
asynchronous Boolean true optional Determines if the primitive will be created asynchronously or block until ready.
debugShowBoundingVolume Boolean false optional For debugging only. Determines if this primitive's commands' bounding spheres are shown.
shadows ShadowMode ShadowMode.DISABLED optional Determines whether this primitive casts or receives shadows from each light source.
Examples:
// 1. Draw a translucent ellipse on the surface with a checkerboard pattern
var instance = new Cesium.GeometryInstance({
  geometry : new Cesium.EllipseGeometry({
      center : Cesium.Cartesian3.fromDegrees(-100.0, 20.0),
      semiMinorAxis : 500000.0,
      semiMajorAxis : 1000000.0,
      rotation : Cesium.Math.PI_OVER_FOUR,
      vertexFormat : Cesium.VertexFormat.POSITION_AND_ST
  }),
  id : 'object returned when this instance is picked and to get/set per-instance attributes'
});
scene.primitives.add(new Cesium.Primitive({
  geometryInstances : instance,
  appearance : new Cesium.EllipsoidSurfaceAppearance({
    material : Cesium.Material.fromType('Checkerboard')
  })
}));
// 2. Draw different instances each with a unique color
var rectangleInstance = new Cesium.GeometryInstance({
  geometry : new Cesium.RectangleGeometry({
    rectangle : Cesium.Rectangle.fromDegrees(-140.0, 30.0, -100.0, 40.0),
    vertexFormat : Cesium.PerInstanceColorAppearance.VERTEX_FORMAT
  }),
  id : 'rectangle',
  attributes : {
    color : new Cesium.ColorGeometryInstanceAttribute(0.0, 1.0, 1.0, 0.5)
  }
});
var ellipsoidInstance = new Cesium.GeometryInstance({
  geometry : new Cesium.EllipsoidGeometry({
    radii : new Cesium.Cartesian3(500000.0, 500000.0, 1000000.0),
    vertexFormat : Cesium.VertexFormat.POSITION_AND_NORMAL
  }),
  modelMatrix : Cesium.Matrix4.multiplyByTranslation(Cesium.Transforms.eastNorthUpToFixedFrame(
    Cesium.Cartesian3.fromDegrees(-95.59777, 40.03883)), new Cesium.Cartesian3(0.0, 0.0, 500000.0), new Cesium.Matrix4()),
  id : 'ellipsoid',
  attributes : {
    color : Cesium.ColorGeometryInstanceAttribute.fromColor(Cesium.Color.AQUA)
  }
});
scene.primitives.add(new Cesium.Primitive({
  geometryInstances : [rectangleInstance, ellipsoidInstance],
  appearance : new Cesium.PerInstanceColorAppearance()
}));
// 3. Create the geometry on the main thread.
scene.primitives.add(new Cesium.Primitive({
  geometryInstances : new Cesium.GeometryInstance({
      geometry : Cesium.EllipsoidGeometry.createGeometry(new Cesium.EllipsoidGeometry({
        radii : new Cesium.Cartesian3(500000.0, 500000.0, 1000000.0),
        vertexFormat : Cesium.VertexFormat.POSITION_AND_NORMAL
      })),
      modelMatrix : Cesium.Matrix4.multiplyByTranslation(Cesium.Transforms.eastNorthUpToFixedFrame(
        Cesium.Cartesian3.fromDegrees(-95.59777, 40.03883)), new Cesium.Cartesian3(0.0, 0.0, 500000.0), new Cesium.Matrix4()),
      id : 'ellipsoid',
      attributes : {
        color : Cesium.ColorGeometryInstanceAttribute.fromColor(Cesium.Color.AQUA)
      }
  }),
  appearance : new Cesium.PerInstanceColorAppearance()
}));
See:

Members

readonlyallowPicking : Boolean

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

appearance : Appearance

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

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

readonlycompressVertices : Boolean

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

cull : Boolean

When true, the renderer frustum culls and horizon culls the primitive's commands based on their bounding volume. Set this to false for a small performance gain if you are manually culling the primitive.
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

depthFailAppearance : Appearance

The Appearance used to shade this primitive when it fails the depth test. Each geometry instance is shaded with the same appearance. Some appearances, like PerInstanceColorAppearance allow giving each instance unique properties.

When using an appearance that requires a color attribute, like PerInstanceColorAppearance, add a depthFailColor per-instance attribute instead.

Requires the EXT_frag_depth WebGL extension to render properly. If the extension is not supported, there may be artifacts.

Default Value: undefined

geometryInstances : Array.<GeometryInstance>|GeometryInstance

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

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

modelMatrix : Matrix4

The 4x4 transformation matrix that transforms the primitive (all geometry instances) from model to world coordinates. When this is the identity matrix, the primitive is drawn in world coordinates, i.e., Earth's WGS84 coordinates. Local reference frames can be used by providing a different transformation matrix, like that returned by Transforms.eastNorthUpToFixedFrame.

This property is only supported in 3D mode.

Default Value: Matrix4.IDENTITY
Example:
var origin = Cesium.Cartesian3.fromDegrees(-95.0, 40.0, 200000.0);
p.modelMatrix = Cesium.Transforms.eastNorthUpToFixedFrame(origin);

readonlyready : 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 Primitive#update is called.

readonlyreadyPromise : Promise.<Primitive>

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

readonlyreleaseGeometryInstances : Boolean

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

shadows : ShadowMode

Determines whether this primitive casts or receives shadows from each light source.
Default Value: ShadowMode.DISABLED

show : Boolean

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

readonlyvertexCacheOptimize : Boolean

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

Methods

destroy() → undefined

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.

Returns:
Throws:
  • DeveloperError : This object was destroyed, i.e., destroy() was called.
Example:
e = e && e.destroy();
See:

getGeometryInstanceAttributes(id) → Object

Returns the modifiable per-instance attributes for a GeometryInstance.
Name Type Description
id Object 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);
attributes.distanceDisplayCondition = Cesium.DistanceDisplayConditionGeometryInstanceAttribute.toValue(100.0, 10000.0);

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:

setPolygonOffset(polyOffsetFactor, polyOffsetUnits)

设置primitive多边形偏移（目前仅支持面）。
Name Type Description
polyOffsetFactor Number 多边形的偏移常量。当值为正值时表示多边形朝屏幕外偏移，为负值时表示朝屏幕内测偏移
polyOffsetUnits Number 多边形缩放因子。多边形缩放因子和偏移常量共同决定了多边形对象在屏幕深度方向的偏移量，可用于解决多边形重叠时闪烁的问题。

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 : Primitive.modelMatrix is only supported in 3D mode.
  • RuntimeError : Vertex texture fetch support is required to render primitives with per-instance attributes. The maximum number of vertex texture image units must be greater than zero.