# GroundPrimitive

#### new Cesium.GroundPrimitive(options)
Scene/GroundPrimitive.js 113

  A ground primitive represents geometry draped over the terrain in the `Scene`. The geometry must be from a single `GeometryInstance`. Batching multiple geometries is not yet supported.

  A primitive combines the geometry instance 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 the `PerInstanceColorAppearance` is supported at this time.

  Valid geometries are `CircleGeometry`, `CorridorGeometry`, `EllipseGeometry`, `PolygonGeometry`, and `RectangleGeometry`.

  Name | Type | Description
  --- | --- | ---
  `options` | Object | optional Object with the following properties:
  Name | Type | Default | Description
  --- | --- | --- | ---
  `geometryInstance` | GeometryInstance |  | optional A single geometry instance to render.
  `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.
  `debugShowBoundingVolume` | Boolean | `false` | optional For debugging only. Determines if this primitive's commands' bounding spheres are shown.

  ##### Example:

      var rectangleInstance = new Cesium.GeometryInstance({
        geometry : new Cesium.RectangleGeometry({
          rectangle : Cesium.Rectangle.fromDegrees(-140.0, 30.0, -100.0, 40.0)
        }),
        id : 'rectangle',
        attributes : {
          color : new Cesium.ColorGeometryInstanceAttribute(0.0, 1.0, 1.0, 0.5)
        }
      });
      scene.primitives.add(new Cesium.GroundPrimitive({
        geometryInstance : rectangleInstance
      }));

  ##### See:

  - Primitive
  - GeometryInstance
  - Appearance

### Members

#### readonlyallowPicking : Boolean
Scene/GroundPrimitive.js 244

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

#### readonlyasynchronous : Boolean
Scene/GroundPrimitive.js 260

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

#### readonlycompressVertices : Boolean
Scene/GroundPrimitive.js 276

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

#### debugShowBoundingVolume : Boolean
Scene/GroundPrimitive.js 148

  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`

#### geometryInstance : Array
Scene/GroundPrimitive.js 128

  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.

  Default Value: `undefined`

#### readonlyinterleave : Boolean
Scene/GroundPrimitive.js 212

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

#### readonlyready : Boolean
Scene/GroundPrimitive.js 292

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

#### readonlyreadyPromise : Promise.<GroundPrimitive>
Scene/GroundPrimitive.js 304

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

#### readonlyreleaseGeometryInstances : Boolean
Scene/GroundPrimitive.js 228

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

#### show : Boolean
Scene/GroundPrimitive.js 137

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

#### readonlyvertexCacheOptimize : Boolean
Scene/GroundPrimitive.js 196

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

### Methods

#### staticCesium.GroundPrimitive.isSupported(scene) → Boolean
Scene/GroundPrimitive.js 317

  Determines if GroundPrimitive rendering is supported.

  Name | Type | Description
  --- | --- | ---
  `scene` | Scene | The scene.

  ##### Returns:

  `true` if GroundPrimitives are supported; otherwise, returns `false`

#### destroy() → undefined
Scene/GroundPrimitive.js 802

  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:

  - GroundPrimitive#isDestroyed

#### getGeometryInstanceAttributes(id) → Object
Scene/GroundPrimitive.js 759

  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);

#### isDestroyed() → Boolean
Scene/GroundPrimitive.js 779

  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:

  - GroundPrimitive#destroy

#### update()
Scene/GroundPrimitive.js 677

  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.