Refactor fog handling and add reflection update timestamp

src/runtime-three/runtime-host.ts

@@ -786,18 +786,12 @@ export class RuntimeHost {
         : null;
 
     if (fogState === null) {
-      if (this.scene.fog !== null) {
-        this.scene.fog = null;
-      }
+      this.underwaterSceneFog.density = 0;
       return;
     }
 
     this.underwaterSceneFog.color.set(fogState.colorHex);
     this.underwaterSceneFog.density = fogState.density;
-
-    if (this.scene.fog !== this.underwaterSceneFog) {
-      this.scene.fog = this.underwaterSceneFog;
-    }
   }
 
   private getWaterReflectionMode() {

src/viewport-three/viewport-host.ts

@@ -190,6 +190,7 @@ interface ViewportWaterSurfaceBinding {
   reflectionMatrixUniform: { value: Matrix4 } | null;
   reflectionEnabledUniform: { value: number } | null;
   reflectionRenderTarget: WebGLRenderTarget | null;
+  lastReflectionUpdateTime: number;
 }
 
 const BRUSH_SELECTED_EDGE_COLOR = 0xf7d2aa;
@@ -253,6 +254,7 @@ const GIZMO_RENDER_ORDER = 4_000;
 const SCALE_SNAP_STEP = 0.1;
 const MIN_SCALE_COMPONENT = 0.1;
 const MIN_BOX_SIZE_COMPONENT = 0.01;
+const WATER_REFLECTION_UPDATE_INTERVAL_MS = 96;
 
 interface CachedMaterialTexture {
   signature: string;