折线示例 Example polylines
使用以下命令在集合中添加和删除多段线 Polylines are added and removed from the collection using
PolylineCollection#add
and PolylineCollection#remove.
性能： Performance:
为了获得最佳性能，最好选择几个集合，每个集合都包含许多折线，而不是多个集合，每个集合仅包含几个折线。组织集合，使更新频率相同的折线位于同一个集合中，即不发生变化的折线应位于一个集合中；改变每一帧的多段线应该在另一个集合中；等等。 For best performance, prefer a few collections, each with many polylines, to many collections with only a few polylines each. Organize collections so that polylines with the same update frequency are in the same collection, i.e., polylines that do not change should be in one collection; polylines that change every frame should be in another collection; and so on.
| 名称 Name | 类型 Type | 说明 Description | ||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
options |
object |
可选 optional
具有以下属性的对象： Object with the following properties:
|
示例： Example:
// Create a polyline collection with two polylines
const polylines = new Cesium.PolylineCollection();
polylines.add({
positions : Cesium.Cartesian3.fromDegreesArray([
-75.10, 39.57,
-77.02, 38.53,
-80.50, 35.14,
-80.12, 25.46]),
width : 2
});
polylines.add({
positions : Cesium.Cartesian3.fromDegreesArray([
-73.10, 37.57,
-75.02, 36.53,
-78.50, 33.14,
-78.12, 23.46]),
width : 4
});另见： See:
成员 Members
Draws the bounding sphere for each draw command in the primitive.
-
默认值： Default Value:
false
PolylineCollection#get 迭代集合中的所有折线。 to iterate over all the polylines in the collection.
modelMatrix : Matrix4
Transforms.eastNorthUpToFixedFrame.
-
默认值： Default Value:
Matrix4.IDENTITY-
默认值： Default Value:
true
方法 Methods
add(options) → Polyline
性能： Performance:
打电话后 After calling add, PolylineCollection#update 被调用并且集合的顶点缓冲区被重写 is called and the collection's vertex buffer is rewritten - an O(n) 操作也会产生 CPU 到 GPU 的开销。为了获得最佳性能，请在调用之前添加尽可能多的折线 operation that also incurs CPU to GPU overhead. For best performance, add as many polylines as possible before calling update.
| 名称 Name | 类型 Type | 说明 Description |
|---|---|---|
options |
object | 可选 optional 描述折线属性的模板，如示例 1 所示。 A template describing the polyline's properties as shown in Example 1. |
返回： Returns:
抛出： Throws:
-
DeveloperError : This object was destroyed, i.e., destroy() was called.
示例： Example:
// Example 1: Add a polyline, specifying all the default values.
const p = polylines.add({
show : true,
positions : ellipsoid.cartographicArrayToCartesianArray([
Cesium.Cartographic.fromDegrees(-75.10, 39.57),
Cesium.Cartographic.fromDegrees(-77.02, 38.53)]),
width : 1
});另见： See:
| 名称 Name | 类型 Type | 说明 Description |
|---|---|---|
polyline |
Polyline | 要检查的折线。 The polyline to check for. |
返回： Returns:
另见： See:
一旦对象被销毁，就不应再使用；调用除 Once an object is destroyed, it should not be used; calling any function other than
isDestroyed 将导致 will result in a DeveloperError 例外。因此，分配返回值（ exception. Therefore, assign the return value (undefined) 到对象，如示例中所做的那样。 ) to the object as done in the example.
抛出： Throws:
-
DeveloperError : This object was destroyed, i.e., destroy() was called.
示例： Example:
polylines = polylines && polylines.destroy();另见： See:
get(index) → Polyline
PolylineCollection#length 迭代集合中的所有折线。 to iterate over all the polylines in the collection.
性能： Performance:
如果从集合中删除折线并且 If polylines were removed from the collection and
PolylineCollection#update 没有被调用，隐式的 was not called, an implicit O(n)
执行操作。 operation is performed.
| 名称 Name | 类型 Type | 说明 Description |
|---|---|---|
index |
number | 折线的从零开始的索引。 The zero-based index of the polyline. |
返回： Returns:
抛出： Throws:
-
DeveloperError : This object was destroyed, i.e., destroy() was called.
示例： Example:
// Toggle the show property of every polyline in the collection
const len = polylines.length;
for (let i = 0; i < len; ++i) {
const p = polylines.get(i);
p.show = !p.show;
}另见： See:
如果该对象被破坏，则不应使用它；调用除 If this object was destroyed, it should not be used; calling any function other than
isDestroyed 将导致 will result in a DeveloperError exception.
返回： Returns:
true 如果该物体被摧毁；否则， if this object was destroyed; otherwise, false.
另见： See:
性能： Performance:
打电话后 After calling remove, PolylineCollection#update 被调用并且集合的顶点缓冲区被重写 is called and the collection's vertex buffer is rewritten - an O(n) 操作也会产生 CPU 到 GPU 的开销。为了获得最佳性能，请在调用之前删除尽可能多的折线 operation that also incurs CPU to GPU overhead. For best performance, remove as many polylines as possible before calling update。如果您打算暂时隐藏多段线，通常调用更有效 . If you intend to temporarily hide a polyline, it is usually more efficient to call
Polyline#show 而不是删除并重新添加折线。 instead of removing and re-adding the polyline.
| 名称 Name | 类型 Type | 说明 Description |
|---|---|---|
polyline |
Polyline | 要删除的折线。 The polyline to remove. |
返回： Returns:
true 如果折线被删除； if the polyline was removed; false 如果在集合中未找到折线。 if the polyline was not found in the collection.
抛出： Throws:
-
DeveloperError : This object was destroyed, i.e., destroy() was called.
示例： Example:
const p = polylines.add(...);
polylines.remove(p); // Returns true另见： See:
性能： Performance:
O(n)。从集合中删除所有折线然后添加新折线比完全创建新集合更有效。 . It is more efficient to remove all the polylines from a collection and then add new ones than to create a new collection entirely.
抛出： Throws:
-
DeveloperError : This object was destroyed, i.e., destroy() was called.
示例： Example:
polylines.add(...);
polylines.add(...);
polylines.removeAll();另见： See:
Viewer or CesiumWidget 渲染场景以获取渲染此图元所需的绘制命令。 render the scene to get the draw commands needed to render this primitive.
不要直接调用该函数。记录此内容只是为了列出渲染场景时可能传播的异常： Do not call this function directly. This is documented just to list the exceptions that may be propagated when the scene is rendered:
抛出： Throws:
-
RuntimeError ：需要顶点纹理获取支持来渲染具有每个实例属性的图元。顶点纹理图像单元的最大数量必须大于零。 : 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.