new Cesium.Primitive(options)

A primitive represents geometry in the Scene. The geometry can be from a single GeometryInstance 如下文例1所示,或从一系列实例来看,即使几何不同 几何类型, e.g .,一个 RectangleGeometry ,一个 EllipsoidGeometry ,如代码例2所示.

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, 而外观则定义了视觉特征. 调和几何和外观,让我们可以混合 并匹配其中的大部分,并添加一个新的几何或外观,彼此独立.

将多个实例合并成一个原始的,叫做批量,大大改善了静态数据的性能. 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 可以创建并分批在网络工人上或主线上. 前两个例子 显示将使用几何描述在网络工作者上创建的几何。 第三个实例 通过明确调用 NT 0 createGeometry NT 1 方法来显示如何在主线上创建几何.

Name Type Description
options object optional 下列属性的对象 :
Name Type Default Description
geometryInstances Array.<GeometryInstance> | GeometryInstance optional 几何实例- 或单一几何实例- 要渲染 .
appearance Appearance optional 用来制造原始的外表.
depthFailAppearance Appearance optional 用来遮蔽这个原始物的外观 当它失败的深度测试.
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 light sources.
Examples:
// 1. Draw a translucent ellipse on the surface with a checkerboard pattern
const 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
const 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)
  }
});
const 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(),
  asynchronous : false
}));
See:

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

appearance : Appearance

The Appearance used to shade this primitive. Each geometry 实例以相同的外观遮蔽。 一些外表,比如说 PerInstanceColorAppearance allow giving each instance unique properties.
Default Value: undefined

readonly asynchronous : boolean

确定是否创建几何实例并在网络工人上进行分批.
Default Value: true

readonly compressVertices : boolean

当 NT 0 real NT 1 时,几何顶点被压缩,这将保存内存.
Default Value: true

cull : boolean

When true, the renderer frustum culls and horizon culls the primitive's commands 依据其范围。 设定为 NT 0 false NT 1 ,以获得小的性能收益 如果你手动抚摸原始人.
Default Value: true

debugShowBoundingVolume : boolean

此属性仅用于调试;不用于生产,也不优化.

绘制原始中每个绘图命令的边框.

Default Value: false

depthFailAppearance : Appearance

Appearance 在深度测试失败时用来遮蔽这个原始的. 每个几何 实例以相同的外观遮蔽。 一些外表,比如说 PerInstanceColorAppearance allow giving each instance unique properties.

当使用一个需要色彩属性的外观时,比如PerInstance ColorAppearance, 添加深度FailColor / 内置属性.

需要 EXT frag 深度 WebGL 扩展以正确渲染 。 如果不支持扩展, 可能还有文物.

Default Value: undefined

readonly geometryInstances : Array.<GeometryInstance>|GeometryInstance

用这个原始的几何学实例。 这可能 如果 NT 0 未定义 NT 1 如果 NT 4 is true when the primitive is constructed.

原始化后改变这个属性没有效果.

Default Value: undefined

readonly interleave : boolean

确定几何顶点属性是否互换,这可以略微改善渲染性能.
Default Value: false

modelMatrix : Matrix4

将原始(所有几何实例)从模型转化为世界坐标的4x4变换矩阵. 当这是身份矩阵时, 原始的被绘制在世界坐标中, i.e . 地球的 WGS84 坐标. 本地参考框架可以通过提供不同的变换矩阵来使用, 如返回的变换矩阵 by Transforms.eastNorthUpToFixedFrame.

此属性仅以3D 模式支持 .

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

readonly ready : boolean

确定原始的是否完整,是否准备制成. 如果这是 true, the primitive will be rendered the next time that Primitive#update is called.
Example:
// Wait for a primitive to become ready before accessing attributes
const removeListener = scene.postRender.addEventListener(() => {
  if (!frustumPrimitive.ready) {
    return;
  }

  const attributes = primitive.getGeometryInstanceAttributes('an id');
  attributes.color = Cesium.ColorGeometryInstanceAttribute.toValue(Cesium.Color.AQUA);

  removeListener();
});

readonly releaseGeometryInstances : boolean

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

shadows : ShadowMode

确定这种原始的铸造或接收来自光源的阴影.
Default Value: ShadowMode.DISABLED

show : boolean

确定是否将显示原始文件 。 这影响到所有几何 原始中的例子.
Default Value: true

readonly vertexCacheOptimize : boolean

当 NT 0 true NT 1 时,几何顶点被优化为前端和后端阴影缓存.
Default Value: true

Methods

destroy()

Destroys the WebGL resources held by this object. Destroying an object allows for deterministic 释放 WebGL 资源,而不是依赖垃圾收集器来摧毁此对象.

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

Returns the modifiable per-instance attributes for a GeometryInstance.
Name Type Description
id * The id of the GeometryInstance.
Returns:
在属性格式中键入的数组, 如果无 id 实例, 则未定义 .
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);
attributes.distanceDisplayCondition = Cesium.DistanceDisplayConditionGeometryInstanceAttribute.toValue(100.0, 10000.0);
attributes.offset = Cesium.OffsetGeometryInstanceAttribute.toValue(Cartesian3.IDENTITY);

isDestroyed() → boolean

如果此对象被销毁, 返回真实; 否则, 错误 .

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()

Called when Viewer or CesiumWidget render the scene to 获得使这个原始化所需的绘图命令.

不要直接调用此函数 。 记录下来的只是 列出场景拍摄时可能宣传的例外情况:

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.
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