new model viewer fix 3

src/client/viewer/main.ts

@@ -20,6 +20,7 @@ let renderer: THREE.WebGLRenderer
 let scene:    THREE.Scene
 let camera:   THREE.PerspectiveCamera
 let controls: OrbitControls
+let keyLight: THREE.DirectionalLight
 
 // ---- UI helpers ----------------------------------------------------------
 
@@ -80,13 +81,12 @@ function buildScene(canvas: HTMLCanvasElement) {
   const ambient = new THREE.AmbientLight(0xffffff, 0.5)
   scene.add(ambient)
 
-  const key = new THREE.DirectionalLight(0xffffff, 2.0)
-  key.position.set(10, 20, 10)
-  key.castShadow = true
-  key.shadow.mapSize.set(2048, 2048)
-  key.shadow.camera.near = 0.1
-  key.shadow.camera.far  = 500
-  scene.add(key)
+  keyLight = new THREE.DirectionalLight(0xffffff, 2.0)
+  keyLight.position.set(10, 20, 10)
+  keyLight.castShadow = true
+  keyLight.shadow.mapSize.set(2048, 2048)
+  scene.add(keyLight)
+  scene.add(keyLight.target)
 
   const fill = new THREE.DirectionalLight(0x8899cc, 0.4)
   fill.position.set(-10, 5, -10)
@@ -150,6 +150,31 @@ function fitCamera(object: THREE.Object3D) {
   camera.lookAt(center)
   controls.target.copy(center)
   controls.update()
+
+  // Scale fog so it stays subtle at any model size.
+  // density = 0.19/dist keeps fog-factor ≈ 0.95 at the viewing distance.
+  if (scene.fog instanceof THREE.FogExp2) {
+    scene.fog.density = 0.19 / dist
+  }
+
+  // Aim key light at the model center and fit its shadow frustum around
+  // the model so shadows are correct regardless of scale.
+  const lightDist = maxDim * 2
+  keyLight.position.set(
+    center.x + lightDist * 0.5,
+    center.y + lightDist,
+    center.z + lightDist * 0.5,
+  )
+  keyLight.target.position.copy(center)
+  keyLight.target.updateMatrixWorld()
+
+  const sc = keyLight.shadow.camera
+  const ext = maxDim * 1.5
+  sc.left   = -ext;  sc.right  = ext
+  sc.top    = ext;   sc.bottom = -ext
+  sc.near   = lightDist * 0.1
+  sc.far    = lightDist * 4
+  sc.updateProjectionMatrix()
 }
 
 // ---- Ground grid ---------------------------------------------------------