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:
|
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
-
When
true
, each geometry instance will only be pickable withScene#pick
. Whenfalse
, 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, likePerInstanceColorAppearance
allow giving each instance unique properties.-
Default Value:
undefined
-
Determines if the geometry instances will be created and batched on a web worker.
-
Default Value:
true
-
When
true
, geometry vertices are compressed, which will save memory.-
Default Value:
true
-
When
true
, the renderer frustum culls and horizon culls the primitive's commands based on their bounding volume. Set this tofalse
for a small performance gain if you are manually culling the primitive.-
Default Value:
true
-
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, likePerInstanceColorAppearance
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
-
readonlygeometryInstances : Array.<GeometryInstance>|GeometryInstance
-
The geometry instances rendered with this primitive. This may be
undefined
ifoptions.releaseGeometryInstances
istrue
when the primitive is constructed.Changing this property after the primitive is rendered has no effect.
-
Default Value:
undefined
-
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);
-
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.
-
When
true
, the primitive does not keep a reference to the inputgeometryInstances
to save memory.-
Default Value:
true
-
shadows : ShadowMode
-
Determines whether this primitive casts or receives shadows from each light source.
-
Default Value:
ShadowMode.DISABLED
-
Determines if the primitive will be shown. This affects all geometry instances in the primitive.
-
Default Value:
true
-
When
true
, geometry vertices are optimized for the pre and post-vertex-shader caches.-
Default Value:
true
Methods
-
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 aDeveloperError
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:
-
-
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);
-
-
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 aDeveloperError
exception.Returns:
true
if this object was destroyed; otherwise,false
.See:
-
Called when
Viewer
orCesiumWidget
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.
-