fix(ifc): avoid merging adjacent wall assemblies

packages/ifc-converter/src/cleanup.ts

@@ -199,13 +199,23 @@ function toWallSegment(wall: WallNode): WallSegment | null {
 }
 
 function wallLineTolerance(a: WallSegment, b: WallSegment) {
-  return Math.max(0.06, Math.min(0.14, Math.max(a.thickness, b.thickness) * 0.5))
+  // Fragments must share essentially the same centerline. A tolerance based on
+  // half the wall thickness can collapse adjacent walls whose faces merely meet.
+  return Math.max(0.005, Math.min(0.025, Math.max(a.thickness, b.thickness) * 0.1))
 }
 
 function wallHeightCompatible(a: WallSegment, b: WallSegment) {
   return Math.abs(a.height - b.height) <= WALL_HEIGHT_TOLERANCE
 }
 
+function wallMaterialCompatible(a: WallSegment, b: WallSegment) {
+  const materialA = (a.wall.metadata as { material?: unknown } | undefined)?.material
+  const materialB = (b.wall.metadata as { material?: unknown } | undefined)?.material
+  const nameA = typeof materialA === 'string' ? materialA : null
+  const nameB = typeof materialB === 'string' ? materialB : null
+  return nameA === nameB
+}
+
 function wallIntervalsCompatible(a: WallSegment, b: WallSegment, maxJoinGap: number) {
   const gap = Math.max(a.t0, b.t0) - Math.min(a.t1, b.t1)
   if (gap <= maxJoinGap) return true
@@ -220,6 +230,7 @@ function wallsCanMerge(a: WallSegment, b: WallSegment, maxJoinGap: number) {
   if (Math.abs(a.angleBucket - b.angleBucket) > 1) return false
   if (Math.abs(a.offset - b.offset) > wallLineTolerance(a, b)) return false
   if (!wallHeightCompatible(a, b)) return false
+  if (!wallMaterialCompatible(a, b)) return false
   return wallIntervalsCompatible(a, b, maxJoinGap)
 }
 

packages/ifc-converter/tests/cleanup.test.ts

@@ -85,6 +85,51 @@ describe('simplifyConvertedSceneGraph', () => {
     expect((nodes.level_1 as { children: string[] }).children).toEqual([keptWall?.id])
   })
 
+  it('does not merge parallel wall fragments on centerlines offset by two inches', () => {
+    const nodes: Record<string, AnyNode> = {
+      level_1: level('level_1', ['wall_a', 'wall_b']),
+      wall_a: wall('wall_a', [0, 0], [2, 0]),
+      wall_b: wall('wall_b', [2, 0.0508], [4, 0.0508]),
+    }
+
+    const stats = simplifyConvertedSceneGraph(nodes)
+
+    expect(stats.removedMergedWalls).toBe(0)
+    expect(Object.values(nodes).filter((node) => node.type === 'wall')).toHaveLength(2)
+  })
+
+  it('does not merge collinear wall fragments with different IFC materials', () => {
+    const exterior = wall('wall_exterior', [0, 0], [2, 0])
+    const interior = wall('wall_interior', [2.9, 0], [5, 0])
+    exterior.metadata = { material: 'Exterior Finish Assembly' }
+    interior.metadata = { material: 'Interior Partition Assembly' }
+    const nodes: Record<string, AnyNode> = {
+      level_1: level('level_1', ['wall_exterior', 'wall_interior']),
+      wall_exterior: exterior,
+      wall_interior: interior,
+    }
+
+    const stats = simplifyConvertedSceneGraph(nodes)
+
+    expect(stats.removedMergedWalls).toBe(0)
+    expect(Object.values(nodes).filter((node) => node.type === 'wall')).toHaveLength(2)
+  })
+
+  it('does not merge a material-tagged wall with an untagged wall', () => {
+    const tagged = wall('wall_tagged', [0, 0], [2, 0])
+    tagged.metadata = { material: 'Exterior Finish Assembly' }
+    const nodes: Record<string, AnyNode> = {
+      level_1: level('level_1', ['wall_tagged', 'wall_unknown']),
+      wall_tagged: tagged,
+      wall_unknown: wall('wall_unknown', [2.9, 0], [5, 0]),
+    }
+
+    const stats = simplifyConvertedSceneGraph(nodes)
+
+    expect(stats.removedMergedWalls).toBe(0)
+    expect(Object.values(nodes).filter((node) => node.type === 'wall')).toHaveLength(2)
+  })
+
   it('reprojects openings from removed walls onto the merged wall', () => {
     const nodes: Record<string, AnyNode> = {
       level_1: level('level_1', ['wall_a', 'wall_b']),