viewer: nothing passes through a roof

packages/nodes/src/column/renderer.tsx

@@ -10,6 +10,7 @@ import {
   type ColumnSlotId,
   collectDescendants,
   createSceneApi,
+  getFloorStackedPosition,
   useLiveNodeOverrides,
   useLiveTransforms,
   useRegistry,
@@ -27,6 +28,7 @@ import {
   createSurfaceRoleMaterial,
   NodeRenderer,
   type RenderShading,
+  resolveColumnRoofHeight,
   resolveMaterialRef,
   resolveSlotDefaultMaterial,
   useNodeEvents,
@@ -2246,10 +2248,19 @@ export const ColumnRenderer = ({ node: rawNode }: { node: ColumnNode }) => {
   // hearing the commit on release. Subscribes narrowly to this node's
   // override entry; unrelated writes don't re-render.
   const liveOverride = useLiveNodeOverrides((s) => s.overrides.get(rawNode.id))
-  const node = useMemo<ColumnNode>(
-    () => (liveOverride ? ({ ...rawNode, ...liveOverride } as ColumnNode) : rawNode),
-    [rawNode, liveOverride],
+  // A post under a roof meets its underside (see `resolveColumnRoofHeight`).
+  const roofHeight = useScene((s) =>
+    resolveColumnRoofHeight(
+      rawNode,
+      s.nodes,
+      // The floor-elevation system lifts the column onto its slab; measure from there.
+      getFloorStackedPosition({ node: rawNode, nodes: s.nodes, position: rawNode.position })[1],
+    ),
   )
+  const node = useMemo<ColumnNode>(() => {
+    const merged = liveOverride ? ({ ...rawNode, ...liveOverride } as ColumnNode) : rawNode
+    return roofHeight != null && roofHeight > 0 ? { ...merged, height: roofHeight } : merged
+  }, [rawNode, liveOverride, roofHeight])
   const scriptedColumn = Boolean(node.source)
   const modelData = useMemo(() => ({ scriptedColumn }), [scriptedColumn])
   const handlers = useNodeEvents(node, 'column')

packages/viewer/src/index.ts

@@ -292,6 +292,7 @@ export {
   roofCsgDummyMats,
   type SurfaceFrame,
 } from './systems/roof/roof-system'
+export { resolveColumnRoofHeight } from './systems/roof/roof-underside'
 export { ScanSystem } from './systems/scan/scan-system'
 // Pure slab geometry generator — composed into the registry-driven slab
 // definition's `def.geometry` in `@pascal-app/nodes`.

packages/viewer/src/systems/roof/roof-clip.test.ts

@@ -0,0 +1,47 @@
+// @ts-expect-error — bun:test is provided by the Bun runtime; viewer does not
+// depend on @types/bun so the import type is unresolved at compile time.
+import { describe, expect, test } from 'bun:test'
+import * as THREE from 'three'
+import { clipGeometryByRegions } from './roof-clip'
+
+/** Above y = 1 + 0.3 x, inside 0 ≤ x ≤ 4, 0 ≤ z ≤ 4. */
+const region = [
+  new THREE.Plane(new THREE.Vector3(-0.3, 1, 0), -1),
+  new THREE.Plane(new THREE.Vector3(1, 0, 0), 0),
+  new THREE.Plane(new THREE.Vector3(-1, 0, 0), 4),
+  new THREE.Plane(new THREE.Vector3(0, 0, 1), 0),
+  new THREE.Plane(new THREE.Vector3(0, 0, -1), 4),
+]
+
+function post(x: number, height = 3) {
+  const geometry = new THREE.BoxGeometry(0.2, height, 0.2)
+  geometry.translate(x, height / 2, 2)
+  return geometry
+}
+
+describe('roof clip', () => {
+  test('a post under the slope loses everything above the underside', () => {
+    const clipped = clipGeometryByRegions(post(2), [region])!
+    expect(clipped).not.toBeNull()
+    const positions = clipped.getAttribute('position')
+    for (let i = 0; i < positions.count; i++) {
+      const x = positions.getX(i)
+      expect(positions.getY(i)).toBeLessThanOrEqual(1 + 0.3 * x + 1e-5)
+    }
+    clipped.computeBoundingBox()
+    expect(clipped.boundingBox!.max.y).toBeCloseTo(1 + 0.3 * 2.1, 4)
+    expect(clipped.boundingBox!.min.y).toBeCloseTo(0, 6)
+  })
+
+  test('a post outside the roof outline or below the underside stays as it is', () => {
+    expect(clipGeometryByRegions(post(6), [region])).toBeNull()
+    expect(clipGeometryByRegions(post(2, 0.8), [region])).toBeNull()
+  })
+
+  test('material groups survive the cut', () => {
+    const clipped = clipGeometryByRegions(post(2), [region])!
+    expect(new Set(clipped.groups.map((group) => group.materialIndex)).size).toBeGreaterThan(1)
+    const total = clipped.groups.reduce((sum, group) => sum + group.count, 0)
+    expect(total).toBe(clipped.getAttribute('position').count)
+  })
+})