From 465129eec7e8d5edb4223a5f813f662baa5e8f8f Mon Sep 17 00:00:00 2001
From: rayd1o <qiank@sbuild.cn>
Date: Mon, 23 Mar 2026 03:56:45 +0800
Subject: [PATCH] fix(satellites): use timestamp-based trail filtering to
 prevent flash

- Changed trail data structure to {pos, time} with Date.now() timestamp
- Replaced length-based filtering with time-based filtering (5 second window)
- Trail now naturally clears when page returns to foreground
- No more ugly frame-skipping or visibilitychange workarounds

Build: passes
---
 frontend/public/earth/js/satellites.js | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/frontend/public/earth/js/satellites.js b/frontend/public/earth/js/satellites.js
index 06a513dd..3420b478 100644
--- a/frontend/public/earth/js/satellites.js
+++ b/frontend/public/earth/js/satellites.js
@@ -18,6 +18,7 @@ let lockedRingSprite = null;
 const SATELLITE_API = SATELLITE_CONFIG.apiPath + '?limit=' + SATELLITE_CONFIG.maxCount;
 const MAX_SATELLITES = SATELLITE_CONFIG.maxCount;
 const TRAIL_LENGTH = SATELLITE_CONFIG.trailLength;
+const TRAIL_MAX_AGE_MS = 5000; // 5 seconds
 const DOT_TEXTURE_SIZE = 32;
 
 function createCircularDotTexture() {
@@ -244,10 +245,10 @@ export function updateSatellitePositions(deltaTime = 0) {
     
     satellitePositions[i].current.copy(pos);
     
-    satellitePositions[i].trail.push(pos.clone());
-    if (satellitePositions[i].trail.length > TRAIL_LENGTH) {
-      satellitePositions[i].trail.shift();
-    }
+    satellitePositions[i].trail.push({ pos: pos.clone(), time: Date.now() });
+    satellitePositions[i].trail = satellitePositions[i].trail.filter(
+      p => Date.now() - p.time < TRAIL_MAX_AGE_MS
+    );
     
     positions[i * 3] = pos.x;
     positions[i * 3 + 1] = pos.y;
@@ -281,7 +282,7 @@ export function updateSatellitePositions(deltaTime = 0) {
       const trailIdx = (i * TRAIL_LENGTH + j) * 3;
       
       if (j < trail.length) {
-        const t = trail[j];
+        const t = trail[j].pos;
         trailPositions[trailIdx] = t.x;
         trailPositions[trailIdx + 1] = t.y;
         trailPositions[trailIdx + 2] = t.z;