item surfaces

packages/core/src/schema/nodes/item.ts

@@ -15,6 +15,11 @@ const assetSchema = z.object({
   offset: z.tuple([z.number(), z.number(), z.number()]).default([0, 0, 0]),
   rotation: z.tuple([z.number(), z.number(), z.number()]).default([0, 0, 0]),
   scale: z.tuple([z.number(), z.number(), z.number()]).default([1, 1, 1]),
+  surface: z
+    .object({
+      height: z.number(), // where things rest 
+    })
+    .optional(), // undefined = can't place things on it
 })
 
 export type AssetInput = z.input<typeof assetSchema>
@@ -26,6 +31,7 @@ export const ItemNode = BaseNode.extend({
   position: z.tuple([z.number(), z.number(), z.number()]).default([0, 0, 0]),
   rotation: z.tuple([z.number(), z.number(), z.number()]).default([0, 0, 0]),
   side: z.enum(['front', 'back']).optional(),
+  children: z.array(z.string()).default([]),
 
   // Wall attachment properties (only used when asset.attachTo is "wall" or "wall-side")
   wallId: z.string().optional(),

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

@@ -35,15 +35,19 @@ export const ItemSystem = () => {
           mesh.position.z = (wallThickness / 2) * side;
         }
       } else if (!item.asset.attachTo) {
-        // Floor item: elevate by slab height (using full footprint overlap)
-        const levelId = resolveLevelId(item, nodes)
-        const slabElevation = spatialGridManager.getSlabElevationForItem(
-          levelId,
-          item.position,
-          item.asset.dimensions,
-          item.rotation,
-        )
-        mesh.position.y = slabElevation + item.position[1]
+        // If parented to another item (surface placement), R3F handles positioning via the hierarchy
+        const parentNode = item.parentId ? nodes[item.parentId as AnyNodeId] : undefined
+        if (parentNode?.type !== 'item') {
+          // Floor item: elevate by slab height (using full footprint overlap)
+          const levelId = resolveLevelId(item, nodes)
+          const slabElevation = spatialGridManager.getSlabElevationForItem(
+            levelId,
+            item.position,
+            item.asset.dimensions,
+            item.rotation,
+          )
+          mesh.position.y = slabElevation + item.position[1]
+        }
       }
 
       clearDirty(id as AnyNodeId)

packages/viewer/src/components/renderers/item/item-renderer.tsx

@@ -7,6 +7,7 @@ import { positionLocal, smoothstep, time } from 'three/tsl'
 import { DoubleSide, MeshStandardNodeMaterial } from 'three/webgpu'
 import { useNodeEvents } from '../../../hooks/use-node-events'
 import { resolveCdnUrl } from '../../../lib/asset-url'
+import { NodeRenderer } from '../node-renderer'
 
 // Shared materials to avoid creating new instances for every mesh
 const defaultMaterial = new MeshStandardNodeMaterial({
@@ -43,6 +44,9 @@ export const ItemRenderer = ({ node }: { node: ItemNode }) => {
       <Suspense fallback={<PreviewModel node={node} />}>
         <ModelRenderer node={node} />
       </Suspense>
+      {node.children?.map((childId) => (
+        <NodeRenderer key={childId} nodeId={childId as ItemNode['id']} />
+        ))}
     </group>
   )
 }