性能优化：精简便签每帧计算、地理视图跳过 Three.js 每帧逻辑

src/scene/CesiumGlobe.js

@@ -275,7 +275,13 @@ export class CesiumGlobe {
       const position = Cesium.Cartesian3.fromDegrees(entry.lng, entry.lat);
       const noteNormal = makeStickyNote(entry.name, 16, false);
       const noteSelected = makeStickyNote(entry.name, 16, true);
-      this.markers.push({ position, noteNormal, noteSelected, index: i });
+      this.markers.push({
+        position,
+        r2: Cesium.Cartesian3.magnitudeSquared(position),
+        noteNormal,
+        noteSelected,
+        index: i,
+      });
     });
     this._initMarkerLayer();
   }
@@ -313,6 +319,7 @@ export class CesiumGlobe {
   _updateMarkerLayer() {
     const scene = this.viewer.scene;
     const camera = scene.camera;
+    const camPos = camera.positionWC; // 每帧只取一次相机位置
 
     for (const m of this.markers) {
       const el = m.el;
@@ -321,16 +328,10 @@ export class CesiumGlobe {
       const win = Cesium.SceneTransforms.worldToWindowCoordinates(scene, m.position);
       if (!win) { el.style.display = 'none'; continue; }
 
-      // 前/后半球判断 + 地平线附近渐变淡出（固定 ~3° 渐变带，避免拖拽时闪烁/突隐）
-      const dotPC = Cesium.Cartesian3.dot(m.position, camera.positionWC);
-      const pMag = Math.sqrt(Cesium.Cartesian3.magnitudeSquared(m.position));
-      const cMag = Cesium.Cartesian3.magnitude(camera.positionWC);
-      const cosPhi = dotPC / (pMag * cMag);
-      const phi = Math.acos(Math.max(-1, Math.min(1, cosPhi)));
-      const phiHorizon = Math.acos(Math.max(-1, Math.min(1, pMag / cMag)));
-      const margin = phiHorizon - phi; // > 0 为前半球
-      if (margin <= 0) { el.style.display = 'none'; continue; }
-      const opacity = Math.min(1, margin / 0.05); // 0.05 rad ≈ 3°
+      // 前/后半球：dot(P, C) > |P|²；地平线附近用 frontness 渐变淡出（避免 acos）
+      const frontness = Cesium.Cartesian3.dot(m.position, camPos) - m.r2;
+      if (frontness <= 0) { el.style.display = 'none'; continue; }
+      const opacity = Math.min(1, frontness / (m.r2 * 0.02));
 
       el.style.display = 'block';
       el.style.opacity = String(opacity);