perf: adaptive cloud march length

config.js

@@ -91,6 +91,18 @@ window.CONFIG = {
     // GPU bound. Read once at context creation, so a reload is needed.
     antialias: false,             // false saves GPU fill rate
 
+    // ------------------------------------------------------------------
+    // Performance
+    // ------------------------------------------------------------------
+    // Adaptive cloud raymarch: shortens the cloud march when the debug FPS
+    // drops, and lengthens it again when the scene stays comfortably fast.
+    performance: {
+        adaptiveCloudMarch: true,
+        lowFps: 24,               // reduce march below this FPS
+        highFps: 35,              // restore march above this FPS
+        minCloudMarchUnits: 45    // never shorten below this raymarch length
+    },
+
     // ------------------------------------------------------------------
     // Location
     // ------------------------------------------------------------------