draft item-system + elevation

packages/core/src/systems/item/item-system.tsx

@@ -0,0 +1,46 @@
+import { useFrame } from '@react-three/fiber'
+import * as THREE from 'three'
+import { sceneRegistry } from '../../hooks/scene-registry/scene-registry'
+import { spatialGridManager } from '../../hooks/spatial-grid/spatial-grid-manager'
+import { resolveLevelId } from '../../hooks/spatial-grid/spatial-grid-sync'
+import type { AnyNodeId, ItemNode, WallNode } from '../../schema'
+import useScene from '../../store/use-scene'
+
+// ============================================================================
+// ITEM SYSTEM
+// ============================================================================
+
+export const ItemSystem = () => {
+  const { nodes, dirtyNodes, clearDirty } = useScene()
+
+  useFrame(() => {
+    if (dirtyNodes.size === 0) return
+
+    dirtyNodes.forEach((id) => {
+      const node = nodes[id]
+      if (!node || node.type !== 'item') return
+
+      const item = node as ItemNode
+      const mesh = sceneRegistry.nodes.get(id) as THREE.Object3D
+      if (!mesh) return
+
+      if (item.asset.attachTo === 'wall' || item.asset.attachTo === 'wall-side') {
+        // Wall-attached item: offset Z by half the parent wall's thickness
+        const parentWall = item.parentId ? nodes[item.parentId as AnyNodeId] : undefined
+        if (parentWall && parentWall.type === 'wall') {
+          const wallThickness = (parentWall as WallNode).thickness ?? 0.1
+          mesh.position.z = wallThickness / 2
+        }
+      } else if (!item.asset.attachTo) {
+        // Floor item: elevate by slab height
+        const levelId = resolveLevelId(item, nodes)
+        const slabElevation = spatialGridManager.getSlabElevationAt(levelId, item.position[0], item.position[2])
+        mesh.position.y = slabElevation
+      }
+
+      clearDirty(id as AnyNodeId)
+    })
+  })
+
+  return null
+}