revert(viewer): drop distance-based LOD switching from GLB scene

Reverts the LOD switching (0469b256). Rendering lod1/lod2 on zoom-out produced
WebGPU validation errors (invalid bindGroup_object) on real-GPU browsers — not
caught earlier because headless Chromium falls back to the WebGL2 backend, so
the WebGPU path was never exercised. The viewer returns to loading the baked
KTX2 lod0 (still the 22MB->12MB win). LOD switching to revisit with a real-GPU
test loop and on-demand loading instead of preload-all.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/viewer/src/components/viewer/glb-scene.tsx

@@ -13,7 +13,6 @@ import useViewer from '../../store/use-viewer'
 
 /** Vertical gap added per floor in `exploded` level mode (matches LevelSystem). */
 const EXPLODED_GAP = 5
-const LOD_FALLBACK_RADIUS = 10
 
 /** A building floor discovered in the baked GLB, ordered bottom-to-top. */
 export type GlbLevel = { id: `level_${string}`; label: string }
@@ -49,10 +48,6 @@ type PascalExtras = {
 /** The resolved drill target for a raycast hit, given the current selection. */
 type Target = { object: THREE.Object3D; id: string; kind: string; label: string }
 type HitCandidate = { object: THREE.Object3D; point?: THREE.Vector3 }
-type GlbLoadResult = {
-  scene: THREE.Group
-  animations: THREE.AnimationClip[]
-}
 
 function findIdentityAncestor(object: THREE.Object3D): THREE.Object3D | null {
   let current: THREE.Object3D | null = object
@@ -233,49 +228,19 @@ function createZoneWallGeometry(polygon: [number, number][]): THREE.BufferGeomet
  */
 export function GlbScene({
   url,
-  lodUrls,
   onLevelsChange,
   onIdentityChange,
   onHoverChange,
 }: {
   url: string
-  lodUrls?: string[]
   onLevelsChange?: (levels: GlbLevel[]) => void
   onIdentityChange?: (identity: GlbIdentity) => void
   onHoverChange?: (hover: GlbHover) => void
 }) {
-  const urls = useMemo(() => (lodUrls && lodUrls.length > 1 ? lodUrls : [url]), [lodUrls, url])
-  const loadedGltfs = useGLTFKTX2(urls) as unknown as GlbLoadResult | GlbLoadResult[]
-  const gltfs = Array.isArray(loadedGltfs) ? loadedGltfs : [loadedGltfs]
-  const gltf = gltfs[0]!
-  const lodScenes = useMemo(() => gltfs.map((g) => g.scene), [gltfs])
-  // Distance-based LOD. We toggle scene visibility by camera distance to the
-  // building's world-space CENTER — `THREE.LOD` measures distance to its own
-  // origin (0,0,0), which mis-selects levels when the baked scene is offset
-  // from the origin. Interaction stays bound to lod0 only; the simpler levels
-  // are visual-only and appear when the camera pulls well past the building
-  // (so normal + building-view distances keep the interactive lod0).
-  const lodInfo = useMemo(() => {
-    if (lodScenes.length <= 1) return null
-    const box = new THREE.Box3().setFromObject(lodScenes[0]!)
-    const center = box.getCenter(new THREE.Vector3())
-    const radius = box.getBoundingSphere(new THREE.Sphere()).radius
-    const r = Number.isFinite(radius) && radius > 0 ? radius : LOD_FALLBACK_RADIUS
-    return { center, dist1: r * 2.5, dist2: r * 8, maxLevel: lodScenes.length - 1 }
-  }, [lodScenes])
-  useEffect(() => {
-    lodScenes.forEach((scene, i) => {
-      scene.visible = i === 0
-    })
-  }, [lodScenes])
-  useFrame(({ camera }) => {
-    if (!lodInfo) return
-    const d = camera.position.distanceTo(lodInfo.center)
-    const level = Math.min(d >= lodInfo.dist2 ? 2 : d >= lodInfo.dist1 ? 1 : 0, lodInfo.maxLevel)
-    for (let i = 0; i < lodScenes.length; i++) {
-      lodScenes[i]!.visible = i === level
-    }
-  })
+  const gltf = useGLTFKTX2(url) as unknown as {
+    scene: THREE.Group
+    animations: THREE.AnimationClip[]
+  }
   const rootRef = useRef<THREE.Group>(null!)
   const { actions } = useAnimations(gltf.animations, rootRef)
   const camera = useThree((state) => state.camera)
@@ -380,10 +345,7 @@ export function GlbScene({
     const built: ZoneFill[] = []
     for (const entry of zoneEntries) {
       const shape = new THREE.Shape()
-      entry.polygon.forEach(([x, z], i) => {
-        if (i === 0) shape.moveTo(x, -z)
-        else shape.lineTo(x, -z)
-      })
+      entry.polygon.forEach(([x, z], i) => (i === 0 ? shape.moveTo(x, -z) : shape.lineTo(x, -z)))
       shape.closePath()
 
       const floorMaterial = createZoneFloorMaterial(entry.color)
@@ -706,7 +668,6 @@ export function GlbScene({
 
   return (
     <group ref={rootRef}>
-      {/* lod0: the interactive level (identity/selection/zones all bind here). */}
       <primitive
         object={gltf.scene}
         onClick={handleClick}
@@ -714,11 +675,6 @@ export function GlbScene({
         onPointerMove={handlePointerMove}
         onPointerOut={handlePointerOut}
       />
-      {/* Simpler LODs are visual-only; the useFrame above toggles their
-          visibility by camera distance. They carry no interaction handlers. */}
-      {gltfs.slice(1).map((g, i) => (
-        <primitive key={lodScenes[i + 1]?.uuid ?? i} object={g.scene} />
-      ))}
       {/* Floating room labels. Each group's matrix is synced to its zone node
           every frame (above) so the label rides level stacking; the div fades
           with the room fill via a CSS transition. */}

packages/viewer/src/hooks/use-gltf-ktx2.tsx

@@ -1,15 +1,9 @@
 import { useGLTF } from '@react-three/drei'
-import { type ObjectMap, useThree } from '@react-three/fiber'
+import { useThree } from '@react-three/fiber'
 import { MeshoptDecoder } from 'three/examples/jsm/libs/meshopt_decoder.module.js'
-import type { GLTF } from 'three/examples/jsm/loaders/GLTFLoader.js'
 import { ensureKtx2Support, ktx2Loader } from '../lib/ktx2-loader'
 
-type GLTFKTX2Path = string | string[]
-type GLTFKTX2Result<T extends GLTFKTX2Path> = T extends string[]
-  ? Array<GLTF & ObjectMap>
-  : GLTF & ObjectMap
-
-const useGLTFKTX2 = <T extends GLTFKTX2Path>(path: T): GLTFKTX2Result<T> => {
+const useGLTFKTX2 = (path: string): ReturnType<typeof useGLTF> => {
   const gl = useThree((state) => state.gl)
 
   return useGLTF(path, true, true, (loader) => {
@@ -18,7 +12,7 @@ const useGLTFKTX2 = <T extends GLTFKTX2Path>(path: T): GLTFKTX2Result<T> => {
       loader.setKTX2Loader(ktx2Loader as any)
     }
     loader.setMeshoptDecoder(MeshoptDecoder)
-  }) as unknown as GLTFKTX2Result<T>
+  })
 }
 
 export { useGLTFKTX2 }