恢复国家/城市标签距离限制，城市小圆保持常显

src/scene/CesiumGlobe.js

@@ -447,6 +447,9 @@ export class CesiumGlobe {
             style: Cesium.LabelStyle.FILL,
             heightReference: Cesium.HeightReference.CLAMP_TO_GROUND,
             disableDepthTestDistance: 1000, // 1km 内不深度测试（近处不消失），远处仍遮挡背面
+            distanceDisplayCondition: new Cesium.DistanceDisplayCondition(0, 1e7),
+            scaleByDistance: new Cesium.NearFarScalar(1e4, 20 / 15, 6e6, 1.0),
+            translucencyByDistance: new Cesium.NearFarScalar(9e6, 1.0, 1e7, 0.0),
           });
         }
 
@@ -485,6 +488,8 @@ export class CesiumGlobe {
     const scene = this.viewer.scene;
     const textGold = Cesium.Color.fromCssColorString('#e0c46a');
     const black = Cesium.Color.fromCssColorString('#14100d');
+    const ddc = new Cesium.DistanceDisplayCondition(0, 4e6);
+    const tdc = new Cesium.NearFarScalar(2e6, 1.0, 4e6, 0.0);
 
     let cities = [];
     try {
@@ -522,6 +527,8 @@ export class CesiumGlobe {
         pixelOffset: new Cesium.Cartesian2(0, -6),
         heightReference: Cesium.HeightReference.CLAMP_TO_GROUND,
         disableDepthTestDistance: 1000, // 1km 内不深度测试（近处不消失），远处仍遮挡背面
+        distanceDisplayCondition: ddc,
+        translucencyByDistance: tdc,
       });
     }
     this._dataReady();