cesium禁止地形穿透

      viewer.clock.onTick.addEventListener(function () {
        if (viewer.camera.pitch > 0) {
          viewer.scene.screenSpaceCameraController.enableTilt = false;
        }
      });
      var mousePosition, startMousePosition;
      var handler = new Cesium.ScreenSpaceEventHandler(viewer.canvas);
      handler.setInputAction(function (movement) {
        mousePosition = startMousePosition = Cesium.Cartesian3.clone(movement.position);
        handler.setInputAction(function (movement) {
          mousePosition = movement.endPosition;
          var y = mousePosition.y - startMousePosition.y;
          if (y > 0) {
            viewer.scene.screenSpaceCameraController.enableTilt = true;
          }
        }, Cesium.ScreenSpaceEventType.MOUSE_MOVE);
      }, Cesium.ScreenSpaceEventType.MIDDLE_DOWN);

此方法禁止cesium地形穿透