fix: harden measurement geometry (#507)

packages/nodes/src/measurement/surface-query.test.ts

@@ -185,4 +185,61 @@ describe('polygon measurement surface intent', () => {
     tableTop.geometry.dispose()
     material.dispose()
   })
+
+  test('keeps later polygon points on the first plane through a distant occluder', () => {
+    const level = new Group()
+    const material = new MeshBasicMaterial({ side: DoubleSide })
+    const floor = new Mesh(new PlaneGeometry(8, 8), material)
+    const table = new Mesh(new PlaneGeometry(8, 8), material)
+    floor.rotation.x = -Math.PI / 2
+    table.rotation.x = -Math.PI / 2
+    table.position.y = 0.8
+    level.add(floor, table)
+    level.updateMatrixWorld(true)
+
+    const hits = new Raycaster(new Vector3(0, 2, 0), new Vector3(0, -1, 0))
+      .intersectObjects([floor, table])
+      .map((intersection) => ({
+        intersection,
+        targetNodeId: intersection.object === floor ? 'slab_1' : 'item_1',
+      }))
+
+    expect(hits[0]?.targetNodeId).toBe('item_1')
+    expect(
+      selectMeasurementSurfaceHit(hits, level, {
+        kind: 'plane',
+        point: [0, 0, 0],
+        normal: [0, 1, 0],
+      })?.targetNodeId,
+    ).toBe('slab_1')
+
+    floor.geometry.dispose()
+    table.geometry.dispose()
+    material.dispose()
+  })
+
+  test('returns no candidate instead of falling through to a different plane', () => {
+    const level = new Group()
+    const material = new MeshBasicMaterial({ side: DoubleSide })
+    const table = new Mesh(new PlaneGeometry(8, 8), material)
+    table.rotation.x = -Math.PI / 2
+    table.position.y = 0.8
+    level.add(table)
+    level.updateMatrixWorld(true)
+
+    const hits = new Raycaster(new Vector3(0, 2, 0), new Vector3(0, -1, 0))
+      .intersectObject(table)
+      .map((intersection) => ({ intersection, targetNodeId: 'item_1' }))
+
+    expect(
+      selectMeasurementSurfaceHit(hits, level, {
+        kind: 'plane',
+        point: [0, 0, 0],
+        normal: [0, 1, 0],
+      }),
+    ).toBeNull()
+
+    table.geometry.dispose()
+    material.dispose()
+  })
 })

packages/nodes/src/measurement/surface-query.ts

@@ -430,11 +430,6 @@ export function selectMeasurementSurfaceHit(
   const nearest = hits[0] ?? null
   if (!(nearest && preference)) return nearest
 
-  const nearby = hits.filter(
-    (hit) =>
-      hit.intersection.distance <=
-      nearest.intersection.distance + SURFACE_INTENT_MAX_OCCLUSION_DISTANCE,
-  )
   if (preference.kind === 'horizontal') {
     if (
       Math.abs(toLocalSurfaceHit(nearest, levelObject).normal[1]) >=
@@ -443,6 +438,11 @@ export function selectMeasurementSurfaceHit(
       return nearest
     }
     const nodes = useScene.getState().nodes as Record<string, { type: string } | undefined>
+    const nearby = hits.filter(
+      (hit) =>
+        hit.intersection.distance <=
+        nearest.intersection.distance + SURFACE_INTENT_MAX_OCCLUSION_DISTANCE,
+    )
     return (
       nearby.find((hit) => {
         const type = hit.targetNodeId ? nodes[hit.targetNodeId]?.type : undefined
@@ -455,11 +455,11 @@ export function selectMeasurementSurfaceHit(
   }
 
   const preferredNormal = new Vector3(...preference.normal)
-  if (preferredNormal.lengthSq() <= 1e-12) return nearest
+  if (preferredNormal.lengthSq() <= 1e-12) return null
   preferredNormal.normalize()
   const preferredPoint = new Vector3(...preference.point)
   return (
-    nearby.find((hit) => {
+    hits.find((hit) => {
       const localHit = toLocalSurfaceHit(hit, levelObject)
       const normalAlignment = Math.abs(preferredNormal.dot(new Vector3(...localHit.normal)))
       const planeDistance = Math.abs(
@@ -469,7 +469,7 @@ export function selectMeasurementSurfaceHit(
         normalAlignment >= SURFACE_INTENT_MIN_NORMAL_ALIGNMENT &&
         planeDistance <= SURFACE_INTENT_PLANE_TOLERANCE
       )
-    }) ?? nearest
+    }) ?? null
   )
 }
 

packages/nodes/src/measurement/tool.test.ts

@@ -24,6 +24,7 @@ import {
   isMeasurementSurfaceMaterialVisible,
   localNormalToPreviewFrame,
   measurementIntersectionWorldNormal,
+  measurementPolygonSurfacePreference,
   measurementVertexSnapAnchors,
   parseMeasurementExtrusionHeight,
   projectMeasurementPointToAxes,
@@ -526,6 +527,23 @@ describe('measurement axis projection', () => {
   })
 })
 
+describe('polygon measurement plane locking', () => {
+  test('keeps the captured plane when magnetic snapping is bypassed', () => {
+    const plane = { point: [0, 1, 0], normal: [0, 1, 0] } as const
+
+    expect(measurementPolygonSurfacePreference('area', plane, false)).toEqual({
+      kind: 'plane',
+      point: plane.point,
+      normal: plane.normal,
+    })
+    expect(measurementPolygonSurfacePreference('area', null, false)).toBeNull()
+    expect(measurementPolygonSurfacePreference('area', null, true)).toEqual({
+      kind: 'horizontal',
+    })
+    expect(measurementPolygonSurfacePreference('distance', plane, true)).toBeNull()
+  })
+})
+
 describe('measurement draft vertex affordances', () => {
   test('selects the closest handle inside its screen threshold', () => {
     expect(selectClosestMeasurementVertexIndex([18, 7, 10])).toBe(1)

packages/nodes/src/measurement/tool.tsx

@@ -288,14 +288,17 @@ function isMeasurementKind(
   )
 }
 
-function polygonSurfacePreference(
+export function measurementPolygonSurfacePreference(
   kind: MeasurementKind,
   plane: { point: MeasurementPoint; normal: MeasurementPoint } | null,
+  applyMagneticSnap: boolean,
 ): MeasurementSurfacePreference | null {
   if (kind !== 'area' && kind !== 'perimeter' && kind !== 'volume') return null
   return plane
     ? { kind: 'plane', point: plane.point, normal: plane.normal }
-    : { kind: 'horizontal' }
+    : applyMagneticSnap
+      ? { kind: 'horizontal' }
+      : null
 }
 
 function isEffectivelyVisible(object: Object3D): boolean {
@@ -1952,9 +1955,11 @@ export const MeasurementTool: FC = () => {
           lockedGuide:
             applyMagneticSnap && activeDraft.axisGuide?.snapped ? activeDraft.axisGuide : null,
           planarProximityAnchors: getPlanarProximityAnchors(),
-          surfacePreference: applyMagneticSnap
-            ? polygonSurfacePreference(activeDraft.kind, activeDraft.collectionPlane)
-            : null,
+          surfacePreference: measurementPolygonSurfacePreference(
+            activeDraft.kind,
+            activeDraft.collectionPlane,
+            applyMagneticSnap,
+          ),
           applyMagneticSnap,
           showAlignmentGuides: isAlignmentGuideActive(),
         })
@@ -2003,9 +2008,11 @@ export const MeasurementTool: FC = () => {
         anchorOrAnchors: draft.points[draft.points.length - 1] ?? null,
         lockedGuide: applyMagneticSnap && draft.axisGuide?.snapped ? draft.axisGuide : null,
         planarProximityAnchors: getPlanarProximityAnchors(),
-        surfacePreference: applyMagneticSnap
-          ? polygonSurfacePreference(draft.kind, draft.collectionPlane)
-          : null,
+        surfacePreference: measurementPolygonSurfacePreference(
+          draft.kind,
+          draft.collectionPlane,
+          applyMagneticSnap,
+        ),
         applyMagneticSnap,
         showAlignmentGuides: isAlignmentGuideActive(),
       })
@@ -2089,9 +2096,11 @@ export const MeasurementTool: FC = () => {
         anchorOrAnchors: draft.points[draft.points.length - 1] ?? null,
         lockedGuide: applyMagneticSnap && draft.axisGuide?.snapped ? draft.axisGuide : null,
         planarProximityAnchors: getPlanarProximityAnchors(),
-        surfacePreference: applyMagneticSnap
-          ? polygonSurfacePreference(draft.kind, draft.collectionPlane)
-          : null,
+        surfacePreference: measurementPolygonSurfacePreference(
+          draft.kind,
+          draft.collectionPlane,
+          applyMagneticSnap,
+        ),
         applyMagneticSnap,
         showAlignmentGuides: isAlignmentGuideActive(),
       })