Frame rate drops to 18 with two thousand entities

• scene.debugShowFramesPerSecond shows 18 FPS.
• The profile shows EntityCluster and Property.getValue taking over 20 ms per frame while draw calls stay low.
• viewer.entities.values.length is 2000.

1. Comment out the Label and keep only Billboard to see whether labels or icons are the cost.
2. Read viewer.entities.values.length to confirm entities were not added twice.
3. Check viewer.scene.primitives.length, which should not grow by one per station.
4. Check whether each entity gets its own ConstantProperty that could be shared.

Replace the entities with one BillboardCollection using collection.add with position, image, scale 0.8 and verticalOrigin BOTTOM, plus one LabelCollection, so 2000 points become a single primitive and a single draw call. If entities must stay, pass a plain Cartesian3 instead of a Property and keep only interactive key sites as entities.

viewer.scene.debugShowFramesPerSecond = true;
// 左上角显示 18 FPS

console.log('实体数量', viewer.entities.values.length);
console.log('图元数量', viewer.scene.primitives.length);

• Adding a Label per station and expecting billboards to fix the cost, since each label is its own texture.
• Keeping CallbackProperty positions for static stations, forcing per-frame evaluation of data that never changes.