Merge claude/wind-particles-movement-eNrTx: fix wind particles not moving

https://claude.ai/code/session_017TwkSjhzhmTcHKmVG5MWUa

1 files changed, 6 insertions, 4 deletions

diff --git a/android-app/app/src/main/kotlin/org/terst/nav/ui/map/ParticleWindView.kt b/android-app/app/src/main/kotlin/org/terst/nav/ui/map/ParticleWindView.kt
index 26d9ea2..746efb5 100644
--- a/android-app/app/src/main/kotlin/org/terst/nav/ui/map/ParticleWindView.kt
+++ b/android-app/app/src/main/kotlin/org/terst/nav/ui/map/ParticleWindView.kt
@@ -21,7 +21,7 @@ import kotlin.random.Random
  * tail segment, then advance the position by the wind vector.
  *
  * Speed is scaled to the visible viewport so the animation looks consistent at any
- * zoom level: a particle at reference wind (10 kt) crosses ~30% of the screen in
+ * zoom level: a particle at reference wind (10 kt) crosses ~100% of the screen in
  * MAX_AGE seconds.
  *
  * Longitude arithmetic is done in a west-relative [0, lonSpan] coordinate space
@@ -103,8 +103,8 @@ class ParticleWindView @JvmOverloads constructor(
         // Span wraps around antimeridian when lonEast < lonWest (e.g. Pacific viewport)
         val lonSpan = if (lonEast >= lonWest) lonEast - lonWest else lonEast - lonWest + 360f
 
-        // Speed scale: at 10kt a particle crosses 30% of viewport in MAX_AGE seconds.
-        val speedScale = latRange * 0.03f / MAX_AGE
+        // Speed scale: at 10kt a particle crosses 100% of viewport in MAX_AGE seconds.
+        val speedScale = latRange * 0.1f / MAX_AGE
 
         // Geographic travel direction: opposite of the FROM direction.
         val travelRad = Math.toRadians((windDirFromDeg + 180.0) % 360.0)
@@ -139,7 +139,9 @@ class ParticleWindView @JvmOverloads constructor(
                 var newLon = lonWest + Random.nextFloat() * lonSpan
                 if (newLon > 180f) newLon -= 360f
                 particleLon[i] = newLon
-                particleAge[i] = Random.nextFloat() * MAX_AGE
+                // Start fresh so each particle gets a full lifetime to drift across the viewport.
+                // A tiny stagger (0–2 s) desynchronises bursts of simultaneous respawns.
+                particleAge[i] = Random.nextFloat() * 2f
                 continue
             }