使用 3D 卡片渲染程序

仿真 3D 图块采用 OGC 标准 glTF 格式,这意味着您可以使用任何支持 OGC 3D 图块规范的渲染器来构建 3D 可视化效果。例如,Cesium 是一个基础的开源库,用于渲染 3D 可视化。

使用 CesiumJS

CesiumJS 是一个用于在网络上实现 3D 可视化的开源 JavaScript 库。如需详细了解如何使用 CesiumJS,请参阅了解 CesiumJS

用户控制功能

CesiumJS 功能块渲染程序具有一组标准的用户控件。

操作 说明
平移视图 左键点击并拖动
缩放视图 右键点击并拖动,或滚动鼠标滚轮
旋转视图 Ctrl + 左/右点击并拖动,或中键点击并拖动

最佳实践

您可以通过多种方法来缩短 CesiumJS 3D 加载时间。例如:

  • 将以下语句添加到呈现 HTML 中,即可启用并发请求:

    Cesium.RequestScheduler.requestsByServer["tile.googleapis.com:443"] = <REQUEST_COUNT>
    

    REQUEST_COUNT 越高,功能块加载速度越快。但是,在 REQUEST_COUNT 大于 10 且停用缓存的 Chrome 浏览器中加载时,您可能会遇到已知的 Chrome 问题。对于大多数使用场景,我们建议将 REQUEST_COUNT 设为 18,以实现最佳性能。

  • 启用跳过详细级别。如需了解详情,请参阅此 Cesium 问题

通过启用 showCreditsOnScreen: true,确保正确显示数据提供方说明。如需了解详情,请参阅政策

呈现指标

如需确定帧速率,请查看每秒调用 requestAnimationFrame 方法的次数。

如需了解帧延迟时间的计算方式,请查看 PerformanceDisplay 类。

CesiumJS 渲染程序示例

只需提供根图块集网址,您就可以将 CesiumJS 渲染程序与 Map Tiles API 的 3D 图块搭配使用。

简单示例

以下示例会初始化 CesiumJS 渲染程序,然后加载根图块集。

<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <title>CesiumJS 3D Tiles Simple Demo</title>
  <script src="https://ajax.googleapis.com/ajax/libs/cesiumjs/1.105/Build/Cesium/Cesium.js"></script>
  <link href="https://ajax.googleapis.com/ajax/libs/cesiumjs/1.105/Build/Cesium/Widgets/widgets.css" rel="stylesheet">
</head>
<body>
  <div id="cesiumContainer"></div>
  <script>

    // Enable simultaneous requests.
    Cesium.RequestScheduler.requestsByServer["tile.googleapis.com:443"] = 18;

    // Create the viewer.
    const viewer = new Cesium.Viewer('cesiumContainer', {
      imageryProvider: false,
      baseLayerPicker: false,
      geocoder: false,
      globe: false,
      // https://cesium.com/blog/2018/01/24/cesium-scene-rendering-performance/#enabling-request-render-mode
      requestRenderMode: true,
    });

    // Add 3D Tiles tileset.
    const tileset = viewer.scene.primitives.add(new Cesium.Cesium3DTileset({
      url: "https://tile.googleapis.com/v1/3dtiles/root.json?key=YOUR_API_KEY",
      // This property is needed to appropriately display attributions
      // as required.
      showCreditsOnScreen: true,
    }));
  </script>
</body>

如需了解 requestRenderMode,请参阅启用请求渲染模式

HTML 网页会如此处所示地呈现。

Places API 集成

您可以将 CesiumJS 与 Places API 搭配使用,以检索更多信息。您可以使用 Autocomplete widget 前往地点的视口。此示例使用了 Places Autocomplete API(通过按照这些说明启用)和 Maps JavaScript API(通过按照这些说明启用)。

<!DOCTYPE html>
<head>
 <meta charset="utf-8" />
 <title>CesiumJS 3D Tiles Places API Integration Demo</title>
 <script src="https://ajax.googleapis.com/ajax/libs/cesiumjs/1.105/Build/Cesium/Cesium.js"></script>
 <link href="https://ajax.googleapis.com/ajax/libs/cesiumjs/1.105/Build/Cesium/Widgets/widgets.css" rel="stylesheet">
</head>
<body>
 <label for="pacViewPlace">Go to a place: </label>
 <input
   type="text"
   id="pacViewPlace"
   name="pacViewPlace"
   placeholder="Enter a location..."
   style="width: 300px"
 />
 <div id="cesiumContainer"></div>
 <script>
   // Enable simultaneous requests.
   Cesium.RequestScheduler.requestsByServer["tile.googleapis.com:443"] = 18;

   // Create the viewer.
   const viewer = new Cesium.Viewer("cesiumContainer", {
     imageryProvider: false,
     baseLayerPicker: false,
     requestRenderMode: true,
     geocoder: false,
     globe: false,
   });

   // Add 3D Tiles tileset.
   const tileset = viewer.scene.primitives.add(
     new Cesium.Cesium3DTileset({
       url: "https://tile.googleapis.com/v1/3dtiles/root.json?key=YOUR_API_KEY",
       // This property is required to display attributions as required.
       showCreditsOnScreen: true,
     })
   );

   const zoomToViewport = (viewport) => {
     viewer.entities.add({
       polyline: {
         positions: Cesium.Cartesian3.fromDegreesArray([
           viewport.getNorthEast().lng(), viewport.getNorthEast().lat(),
           viewport.getSouthWest().lng(), viewport.getNorthEast().lat(),
           viewport.getSouthWest().lng(), viewport.getSouthWest().lat(),
           viewport.getNorthEast().lng(), viewport.getSouthWest().lat(),
           viewport.getNorthEast().lng(), viewport.getNorthEast().lat(),
         ]),
         width: 10,
         clampToGround: true,
         material: Cesium.Color.RED,
       },
     });
     viewer.flyTo(viewer.entities);
   };

   function initAutocomplete() {
     const autocomplete = new google.maps.places.Autocomplete(
       document.getElementById("pacViewPlace"),
       {
         fields: [
           "geometry",
           "name",
         ],
       }
     );
     autocomplete.addListener("place_changed", () => {
       viewer.entities.removeAll();
       const place = autocomplete.getPlace();
       if (!place.geometry || !place.geometry.viewport) {
         window.alert("No viewport for input: " + place.name);
         return;
       }
       zoomToViewport(place.geometry.viewport);
     });
   }
 </script>
 <script
   async=""
   src="https://maps.googleapis.com/maps/api/js?key=YOUR_API_KEY&libraries=places&callback=initAutocomplete"
 ></script>
</body>

无人机旋转视图

您可以控制镜头,以便在图块集内以动画方式呈现。与 Places API 和 Elevation API 结合使用时,此动画可以模拟任何地图注点的交互式无人机飞行。

此代码示例可带您前往您在 Autocomplete widget 中选择的地点。

<!DOCTYPE html>
<head>
  <meta charset="utf-8" />
  <title>CesiumJS 3D Tiles Rotating Drone View Demo</title>
  <script src="https://ajax.googleapis.com/ajax/libs/cesiumjs/1.105/Build/Cesium/Cesium.js"></script>
  <link href="https://ajax.googleapis.com/ajax/libs/cesiumjs/1.105/Build/Cesium/Widgets/widgets.css" rel="stylesheet">
</head>
<body>
  <label for="pacViewPlace">Go to a place: </label>
  <input type="text" id="pacViewPlace" name="pacViewPlace" placeholder="Enter a location..." style="width: 300px" />
  <div id="cesiumContainer"></div>
  <script>
    // Enable simultaneous requests.
    Cesium.RequestScheduler.requestsByServer["tile.googleapis.com:443"] = 18;

    // Create the viewer and remove unneeded options.
    const viewer = new Cesium.Viewer("cesiumContainer", {
      imageryProvider: false,
      baseLayerPicker: false,
      homeButton: false,
      fullscreenButton: false,
      navigationHelpButton: false,
      vrButton: false,
      sceneModePicker: false,
      geocoder: false,
      globe: false,
      infobox: false,
      selectionIndicator: false,
      timeline: false,
      projectionPicker: false,
      clockViewModel: null,
      animation: false,
      requestRenderMode: true,
    });

    // Add 3D Tile set.
    const tileset = viewer.scene.primitives.add(
      new Cesium.Cesium3DTileset({
        url: "https://tile.googleapis.com/v1/3dtiles/root.json?key=YOUR_API_KEY",
        // This property is required to display attributions.
        showCreditsOnScreen: true,
      })
    );

    // Point the camera at a location and elevation, at a viewport-appropriate distance.
    function pointCameraAt(location, viewport, elevation) {
      const distance = Cesium.Cartesian3.distance(
        Cesium.Cartesian3.fromDegrees(
          viewport.getSouthWest().lng(), viewport.getSouthWest().lat(), elevation),
        Cesium.Cartesian3.fromDegrees(
          viewport.getNorthEast().lng(), viewport.getNorthEast().lat(), elevation)
      ) / 2;
      const target = new Cesium.Cartesian3.fromDegrees(location.lng(), location.lat(), elevation);
      const pitch = -Math.PI / 4;
      const heading = 0;
      viewer.camera.lookAt(target, new Cesium.HeadingPitchRange(heading, pitch, distance));
    }

    // Rotate the camera around a location and elevation, at a viewport-appropriate distance.
    let unsubscribe = null;
    function rotateCameraAround(location, viewport, elevation) {
      if(unsubscribe) unsubscribe();
      pointCameraAt(location, viewport, elevation);
      unsubscribe = viewer.clock.onTick.addEventListener(() => {
        viewer.camera.rotate(Cesium.Cartesian3.UNIT_Z);
      });
    }

    function initAutocomplete() {
      const autocomplete = new google.maps.places.Autocomplete(
        document.getElementById("pacViewPlace"), {
          fields: [
            "geometry",
            "name",
          ],
        }
      );
      
      autocomplete.addListener("place_changed", async () => {
        const place = autocomplete.getPlace();
        
        if (!(place.geometry && place.geometry.viewport && place.geometry.location)) {
          window.alert(`Insufficient geometry data for place: ${place.name}`);
          return;
        }
        // Get place elevation using the ElevationService.
        const elevatorService = new google.maps.ElevationService();
        const elevationResponse =  await elevatorService.getElevationForLocations({
          locations: [place.geometry.location],
        });

        if(!(elevationResponse.results && elevationResponse.results.length)){
          window.alert(`Insufficient elevation data for place: ${place.name}`);
          return;
        }
        const elevation = elevationResponse.results[0].elevation || 10;

        rotateCameraAround(
          place.geometry.location,
          place.geometry.viewport,
          elevation
        );
      });
    }
  </script>
  <script async src="https://maps.googleapis.com/maps/api/js?key=YOUR_API_KEY&libraries=places&callback=initAutocomplete"></script>
</body>

绘制多段线和标签

此代码示例演示了如何向地图添加多段线和标签。您可以向地图添加多段线,以显示行车路线和步行路线、显示属性边界,或计算驾车和步行时长。您还可以在不实际渲染场景的情况下获取属性。

您可以引导用户游览街区,或者显示正在出售的邻近房产,然后向场景中添加广告牌等 3D 对象。

您可以总结行程,列出您查看过的属性,在虚拟对象中显示这些详细信息。

<!DOCTYPE html>
<head>
  <meta charset="utf-8" />
  <title>CesiumJS 3D Tiles Polyline and Label Demo</title>
  <script src="https://ajax.googleapis.com/ajax/libs/cesiumjs/1.105/Build/Cesium/Cesium.js"></script>
  <link 
    href="https://ajax.googleapis.com/ajax/libs/cesiumjs/1.105/Build/Cesium/Widgets/widgets.css"
    rel="stylesheet"
  />
</head>
<body>
  <div id="cesiumContainer"></div>
  <script>
    // Enable simultaneous requests.
    Cesium.RequestScheduler.requestsByServer["tile.googleapis.com:443"] = 18;

    // Create the viewer.
    const viewer = new Cesium.Viewer("cesiumContainer", {
      imageryProvider: false,
      baseLayerPicker: false,
      requestRenderMode: true,
      geocoder: false,
      globe: false,
    });

    // Add 3D Tiles tileset.
    const tileset = viewer.scene.primitives.add(
      new Cesium.Cesium3DTileset({
        url: "https://tile.googleapis.com/v1/3dtiles/root.json?key=YOUR_API_KEY",

        // This property is required to display attributions as required.
        showCreditsOnScreen: true,
      })
    );

    // Draws a circle at the position, and a line from the previous position.
    const drawPointAndLine = (position, prevPosition) => {
      viewer.entities.removeAll();
      if (prevPosition) {
        viewer.entities.add({
          polyline: {
            positions: [prevPosition, position],
            width: 3,
            material: Cesium.Color.WHITE,
            clampToGround: true,
            classificationType: Cesium.ClassificationType.CESIUM_3D_TILE,
          },
        });
      }
      viewer.entities.add({
        position: position,
        ellipsoid: {
          radii: new Cesium.Cartesian3(1, 1, 1),
          material: Cesium.Color.RED,
        },
      });
    };

    // Compute, draw, and display the position's height relative to the previous position.
    var prevPosition;
    const processHeights = (newPosition) => {
      drawPointAndLine(newPosition, prevPosition);

      const newHeight = Cesium.Cartographic.fromCartesian(newPosition).height;
      let labelText = "Current altitude (meters above sea level):\n\t" + newHeight;
      if (prevPosition) {
        const prevHeight =
          Cesium.Cartographic.fromCartesian(prevPosition).height;
        labelText += "\nHeight from previous point (meters):\n\t" + Math.abs(newHeight - prevHeight);
      }
      viewer.entities.add({
        position: newPosition,
        label: {
          text: labelText,
          disableDepthTestDistance: Number.POSITIVE_INFINITY,
          pixelOffset: new Cesium.Cartesian2(0, -10),
          showBackground: true,
          verticalOrigin: Cesium.VerticalOrigin.BOTTOM,
        }
      });

      prevPosition = newPosition;
    };

    const handler = new Cesium.ScreenSpaceEventHandler(viewer.canvas);
    handler.setInputAction(function (event) {
      const earthPosition = viewer.scene.pickPosition(event.position);
      if (Cesium.defined(earthPosition)) {
        processHeights(earthPosition);
      }
    }, Cesium.ScreenSpaceEventType.LEFT_CLICK);
  </script>
</body>

相机轨道

在 Cesium 中,您可以让相机围绕地图注点运行,以避免与建筑物发生碰撞。或者,您也可以在镜头移动时将建筑物设为透明。

首先,将镜头锁定在一个点上,然后可以创建镜头轨道,以展示您的作品。为此,您可以将相机的 lookAtTransform 函数与事件监听器结合使用,如以下代码示例所示。

// Lock the camera onto a point.
const center = Cesium.Cartesian3.fromRadians(
  2.4213211833389243,
  0.6171926869414084,
  3626.0426275055174
);

const transform = Cesium.Transforms.eastNorthUpToFixedFrame(center);

viewer.scene.camera.lookAtTransform(
  transform,
  new Cesium.HeadingPitchRange(0, -Math.PI / 8, 2900)
);

// Orbit around this point.
viewer.clock.onTick.addEventListener(function (clock) {
  viewer.scene.camera.rotateRight(0.005);
});

如需详细了解如何控制摄像头,请参阅控制摄像头

与 Cesium for Unreal 合作

如需将 Cesium for Unreal 插件与 3D Tiles API 搭配使用,请按以下步骤操作。

  1. 安装 Cesium for Unreal 插件。

  2. 创建一个新的 Unreal 项目。

  3. 连接到 Google Photorealistic 3D Tiles API。

    1. 从菜单中依次选择 Cesium > Cesium,打开 Cesium 窗口。

    2. 选择 Blank 3D Tiles Tileset

    3. World Outliner 中,选择此 Cesium3DTileset 即可打开 Details 面板。

    4. 来源From Cesium Ion 更改为 From 网址

    5. 将网址设置为 Google 3D Tiles 网址。

    https://tile.googleapis.com/v1/3dtiles/root.json?key=YOUR_API_KEY
    
    1. 启用在屏幕上显示功劳,以正确显示提供方说明。
  4. 整个世界都很加载了。若要移动到任何 LatLng,请在大纲面板中选择 CesiumGeoreference 项,然后在详细信息面板中修改出发地纬度/经度/高度

使用适用于 Unity 的 Cesium

如需在 Cesium for Unity 中使用仿真图块,请按以下步骤操作。

  1. 创建一个新的 Unity 项目。

  2. 在 Package Manager 部分中添加新的作用域注册表(通过 Editor > Project Settings)。

    • 名称:Cesium

    • 网址:https://unity.pkg.cesium.com

    • 范围:com.cesium.unity

  3. 安装适用于 Unity 的 Cesium 软件包。

  4. 连接到 Google Photorealistic 3D Tiles API。

    1. 从菜单中依次选择 Cesium > Cesium,打开 Cesium 窗口。

    2. 点击 Blank 3D Tiles Tileset

    3. 在左侧面板的 Source 下的 Tileset Source 选项中,选择 From 网址(从网址),而不是“From Cesium Ion”。

    4. 将网址设置为 Google 3D Tiles 网址。

    https://tile.googleapis.com/v1/3dtiles/root.json?key=YOUR_API_KEY
    
    1. 启用在屏幕上显示功劳,以正确显示提供方说明。
  5. 整个世界都很加载了。若要移动到任何 LatLng,请在 Scene Hierarchy 中选择 CesiumGeoreference 项,然后在 Inspector 中修改原点纬度/经度/高度。

使用 deck.gl

deck.gl 由 WebGL 提供支持,是一个开源 JavaScript 框架,用于高性能、大规模的数据可视化。

归因

从图块 gltf asset 中提取 copyright 字段,然后在渲染的视图中显示该字段,以确保正确显示数据提供方说明。如需了解详情,请参阅显示数据归因

deck.gl 渲染程序示例

简单示例

以下示例初始化 deck.gl 渲染程序,然后加载 3D 地点。请务必将代码中的 YOUR_API_KEY 替换为您的实际 API 密钥。

<!DOCTYPE html>
<html>
 <head>
   <title>deck.gl Photorealistic 3D Tiles example</title>
   <script src="https://unpkg.com/deck.gl@latest/dist.min.js"></script>
   <style>
     body { margin: 0; padding: 0;}
     #map { position: absolute; top: 0;bottom: 0;width: 100%;}
     #credits { position: absolute; bottom: 0; right: 0; padding: 2px; font-size: 15px; color: white;
        text-shadow: -1px 0 black, 0 1px black, 1px 0 black, 0 -1px black;}
   </style>
 </head>

 <body>
   <div id="map"></div>
   <div id="credits"></div>
   <script>
     const GOOGLE_API_KEY = YOUR_API_KEY;
     const TILESET_URL = `https://tile.googleapis.com/v1/3dtiles/root.json`;
     const creditsElement = document.getElementById('credits');
     new deck.DeckGL({
       container: 'map',
       initialViewState: {
         latitude: 50.0890,
         longitude: 14.4196,
         zoom: 16,
         bearing: 90,
         pitch: 60,
         height: 200
       },
       controller: {minZoom: 8},
       layers: [
         new deck.Tile3DLayer({
           id: 'google-3d-tiles',
           data: TILESET_URL,
           loadOptions: {
            fetch: {
              headers: {
                'X-GOOG-API-KEY': GOOGLE_API_KEY
              }
            }
          },
           onTilesetLoad: tileset3d => {
             tileset3d.options.onTraversalComplete = selectedTiles => {
               const credits = new Set();
               selectedTiles.forEach(tile => {
                 const {copyright} = tile.content.gltf.asset;
                 copyright.split(';').forEach(credits.add, credits);
                 creditsElement.innerHTML = [...credits].join('; ');
               });
               return selectedTiles;
             }
           }
         })
       ]
     });
   </script>
 </body>
</html>

在 Google 仿真 3D 图块上直观呈现 2D 图层

deck.gl TerrainExtension 可将 2D 数据渲染到 3D 表面上。例如,您可以在仿真 3D 图块几何图形之上叠加建筑物平面图的 GeoJSON。

在以下示例中,我们使用适应仿真 3D 图块表面的多边形直观呈现了一层建筑物。

<!DOCTYPE html>
<html>
 <head>
   <title>Google 3D tiles example</title>
   <script src="https://unpkg.com/deck.gl@latest/dist.min.js"></script>
   <style>
     body { margin: 0; padding: 0;}
     #map { position: absolute; top: 0;bottom: 0;width: 100%;}
     #credits { position: absolute; bottom: 0; right: 0; padding: 2px; font-size: 15px; color: white;
        text-shadow: -1px 0 black, 0 1px black, 1px 0 black, 0 -1px black;}
   </style>
 </head>

 <body>
   <div id="map"></div>
   <div id="credits"></div>
   <script>
     const GOOGLE_API_KEY = YOUR_API_KEY;
     const TILESET_URL = `https://tile.googleapis.com/v1/3dtiles/root.json`;
     const BUILDINGS_URL = 'https://raw.githubusercontent.com/visgl/deck.gl-data/master/examples/google-3d-tiles/buildings.geojson'
     const creditsElement = document.getElementById('credits');
     const deckgl = new deck.DeckGL({
       container: 'map',
       initialViewState: {
         latitude: 50.0890,
         longitude: 14.4196,
         zoom: 16,
         bearing: 90,
         pitch: 60,
         height: 200
       },
       controller: true,
       layers: [
         new deck.Tile3DLayer({
           id: 'google-3d-tiles',
           data: TILESET_URL,
           loadOptions: {
            fetch: {
              headers: {
                'X-GOOG-API-KEY': GOOGLE_API_KEY
              }
            }
          },
          onTilesetLoad: tileset3d => {
             tileset3d.options.onTraversalComplete = selectedTiles => {
               const credits = new Set();
               selectedTiles.forEach(tile => {
                 const {copyright} = tile.content.gltf.asset;
                 copyright.split(';').forEach(credits.add, credits);
                 creditsElement.innerHTML = [...credits].join('; ');
               });
               return selectedTiles;
             }
           },
           operation: 'terrain+draw'
         }),
         new deck.GeoJsonLayer({
           id: 'buildings',
           // This dataset is created by CARTO, using other Open Datasets available. More info at: https://3dtiles.carto.com/#about.
           data: 'https://raw.githubusercontent.com/visgl/deck.gl-data/master/examples/google-3d-tiles/buildings.geojson',
           stroked: false,
           filled: true,
           getFillColor: ({properties}) => {
             const {tpp} = properties;
             // quantiles break
             if (tpp < 0.6249)
               return [254, 246, 181]
             else if (tpp < 0.6780)
               return [255, 194, 133]
             else if (tpp < 0.8594)
               return [250, 138, 118]
             return [225, 83, 131]
           },
           opacity: 0.2,
           extensions: [new deck._TerrainExtension()]
         })
       ]
     });
   </script>
 </body>
</html>