如何防止cesium相机视角翻转至地底下

如何防止cesium相机视角翻转至地底下，以下是方案，亲测可用

      // 禁止相机翻转到地下 start

      var minPitch = -Cesium.Math.PI_OVER_TWO

      var maxPitch = 0

      var minHeight = 200

      viewer.camera.changed.addEventListener(

        function() {

          if (viewer.camera._suspendTerrainAdjustment && viewer.scene.mode === Cesium.SceneMode.SCENE3D) {

            viewer.camera._suspendTerrainAdjustment = false

            viewer.camera._adjustHeightForTerrain()

          }

          // Keep camera in a reasonable pitch range

          var pitch = viewer.camera.pitch;

          if (pitch > maxPitch || pitch < minPitch) {

            viewer.scene.screenSpaceCameraController.enableTilt = false;

            // clamp the pitch

            if (pitch > maxPitch) {

              pitch = maxPitch

            } else if (pitch < minPitch) {

              pitch = minPitch

            }

            var destination = Cesium.Cartesian3.fromRadians(

              viewer.camera.positionCartographic.longitude,

              viewer.camera.positionCartographic.latitude,

              Math.max(viewer.camera.positionCartographic.height, minHeight))

            viewer.camera.setView({

              destination: destination,

              orientation: { pitch: pitch }

            })

            viewer.scene.screenSpaceCameraController.enableTilt = true;

          }

        }

      )

      // 禁止相机翻转到地下 end