Geometry
查阅Mars3D API

new Cesium.Geometry(options)
engine/Source/Core/Geometry.js 67

A geometry representation with attributes forming vertices and optional index data defining primitives. Geometries and an Appearance, which describes the shading, can be assigned to a Primitive for visualization. A Primitive can be created from many heterogeneous - in many cases - geometries for performance.

Geometries can be transformed and optimized using functions in GeometryPipeline.

参数名称 类型 描述信息
options object Object with the following properties:
参数名称 类型 默认值 描述信息
attributes GeometryAttributes Attributes, which make up the geometry's vertices.
primitiveType PrimitiveType PrimitiveType.TRIANGLES 可选 The type of primitives in the geometry.
indices Uint16Array | Uint32Array 可选 Optional index data that determines the primitives in the geometry.
boundingSphere BoundingSphere 可选 An optional bounding sphere that fully enclosed the geometry.
使用示例:
// Create geometry with a position attribute and indexed lines.
const positions = new Float64Array([
  0.0, 0.0, 0.0,
  7500000.0, 0.0, 0.0,
  0.0, 7500000.0, 0.0
]);

const geometry = new Cesium.Geometry({
  attributes : {
    position : new Cesium.GeometryAttribute({
      componentDatatype : Cesium.ComponentDatatype.DOUBLE,
      componentsPerAttribute : 3,
      values : positions
    })
  },
  indices : new Uint16Array([0, 1, 1, 2, 2, 0]),
  primitiveType : Cesium.PrimitiveType.LINES,
  boundingSphere : Cesium.BoundingSphere.fromVertices(positions)
});
Demo:
参考:

成员(属性)

attributes : GeometryAttributes
engine/Source/Core/Geometry.js 118

Attributes, which make up the geometry's vertices. Each property in this object corresponds to a GeometryAttribute containing the attribute's data.

Attributes are always stored non-interleaved in a Geometry.

There are reserved attribute names with well-known semantics. The following attributes are created by a Geometry (depending on the provided VertexFormat.

  • position - 3D vertex position. 64-bit floating-point (for precision). 3 components per attribute. See VertexFormat#position.
  • normal - Normal (normalized), commonly used for lighting. 32-bit floating-point. 3 components per attribute. See VertexFormat#normal.
  • st - 2D texture coordinate. 32-bit floating-point. 2 components per attribute. See VertexFormat#st.
  • bitangent - Bitangent (normalized), used for tangent-space effects like bump mapping. 32-bit floating-point. 3 components per attribute. See VertexFormat#bitangent.
  • tangent - Tangent (normalized), used for tangent-space effects like bump mapping. 32-bit floating-point. 3 components per attribute. See VertexFormat#tangent.

The following attribute names are generally not created by a Geometry, but are added to a Geometry by a Primitive or GeometryPipeline functions to prepare the geometry for rendering.

  • position3DHigh - High 32 bits for encoded 64-bit position computed with GeometryPipeline.encodeAttribute. 32-bit floating-point. 4 components per attribute.
  • position3DLow - Low 32 bits for encoded 64-bit position computed with GeometryPipeline.encodeAttribute. 32-bit floating-point. 4 components per attribute.
  • position2DHigh - High 32 bits for encoded 64-bit 2D (Columbus view) position computed with GeometryPipeline.encodeAttribute. 32-bit floating-point. 4 components per attribute.
  • position2DLow - Low 32 bits for encoded 64-bit 2D (Columbus view) position computed with GeometryPipeline.encodeAttribute. 32-bit floating-point. 4 components per attribute.
  • color - RGBA color (normalized) usually from GeometryInstance#color. 32-bit floating-point. 4 components per attribute.
  • pickColor - RGBA color used for picking. 32-bit floating-point. 4 components per attribute.

使用示例:
geometry.attributes.position = new Cesium.GeometryAttribute({
  componentDatatype : Cesium.ComponentDatatype.FLOAT,
  componentsPerAttribute : 3,
  values : new Float32Array(0)
});
参考:

boundingSphere : BoundingSphere|undefined
engine/Source/Core/Geometry.js 148

An optional bounding sphere that fully encloses the geometry. This is commonly used for culling.
默认值: undefined

indices : Array|undefined
engine/Source/Core/Geometry.js 128

Optional index data that - along with Geometry#primitiveType - determines the primitives in the geometry.
默认值: undefined

primitiveType : PrimitiveType|undefined
engine/Source/Core/Geometry.js 138

The type of primitives in the geometry. This is most often PrimitiveType.TRIANGLES, but can varying based on the specific geometry.
默认值: PrimitiveType.TRIANGLES

方法

static Cesium.Geometry.computeNumberOfVertices(geometry) → number
engine/Source/Core/Geometry.js 177

Computes the number of vertices in a geometry. The runtime is linear with respect to the number of attributes in a vertex, not the number of vertices.
参数名称 类型 描述信息
geometry Geometry The geometry.
返回值:
The number of vertices in the geometry.
使用示例:
const numVertices = Cesium.Geometry.computeNumberOfVertices(geometry);
CtrlK
packages/engine
packages/widgets