Validate measurement snap cache signature

CHANGELOG.md

@@ -10,6 +10,7 @@
 - UI: require the locked measurement target to be the frontmost normal pick before snapping, preventing hidden target geometry behind another part from receiving ruler endpoints.
 - UI: clear stale measurement snap status after cancelling a pending endpoint so the selected-object ruler returns to a neutral ready state.
 - Performance: cache selected-target measurement snap candidates while measuring so hover previews do not repeatedly rebuild vertex and edge lists for the same object.
+- Performance: validate selected-target measurement snap caches against target mesh signatures so transformed or updated geometry rebuilds snap candidates instead of reusing stale vertex and edge lists.
 - UI: restyle distance measurements as orthographic drawing-style dimension callouts with extension lines, arrowheads, and compact drafting labels instead of thick freehand ruler lines.
 - UI: remove the preview canvas native hover tooltip while preserving keyboard shortcut metadata for accessibility.
 - UI: clarify render scale versus measurement scale by showing render resolution as percentages, syncing the toolbar to the active renderer budget, and applying the configured scale to `3dgrid`.

src/render/babylon/scene.ts

@@ -315,6 +315,7 @@ export class BabylonModelPreview implements WorkbenchPreview {
   private measurementTargetMeshes: AbstractMesh[] = [];
   private measurementSnapInputCache: MeasurementGeometrySnapInput | null = null;
   private measurementSnapInputCacheTargetId: number | null = null;
+  private measurementSnapInputCacheSignature: string | null = null;
   private measurementSnapKind: MeasurementSnapKind | null = null;
   private readonly measurementObservers = new Set<() => void>();
   private pendingPoint: Vector3 | null = null;
@@ -1955,6 +1956,7 @@ export class BabylonModelPreview implements WorkbenchPreview {
   private invalidateMeasurementSnapInputCache(): void {
     this.measurementSnapInputCache = null;
     this.measurementSnapInputCacheTargetId = null;
+    this.measurementSnapInputCacheSignature = null;
   }
 
   private getMeasurementTargetName(): string | null {
@@ -1997,11 +1999,16 @@ export class BabylonModelPreview implements WorkbenchPreview {
   private createMeasurementGeometrySnapInput(): MeasurementGeometrySnapInput | null {
     const target = this.measurementTargetNode;
     if (!this.rootMesh || !target || isBabylonNodeDisposed(target)) return null;
-    if (this.measurementSnapInputCache && this.measurementSnapInputCacheTargetId === target.uniqueId) {
-      return this.measurementSnapInputCache;
-    }
     const meshes = this.getMeasurementTargetMeshes(target);
     if (meshes.length === 0) return null;
+    const signature = this.createMeasurementSnapInputSignature(meshes);
+    if (
+      this.measurementSnapInputCache &&
+      this.measurementSnapInputCacheTargetId === target.uniqueId &&
+      this.measurementSnapInputCacheSignature === signature
+    ) {
+      return this.measurementSnapInputCache;
+    }
 
     const vertices: MeasurementSnapVertexCandidate[] = [];
     const edges: MeasurementSnapEdgeCandidate[] = [];
@@ -2036,9 +2043,25 @@ export class BabylonModelPreview implements WorkbenchPreview {
     };
     this.measurementSnapInputCache = input;
     this.measurementSnapInputCacheTargetId = target.uniqueId;
+    this.measurementSnapInputCacheSignature = signature;
     return input;
   }
 
+  private createMeasurementSnapInputSignature(meshes: readonly AbstractMesh[]): string {
+    return meshes.map((mesh) => {
+      const geometryId = "geometry" in mesh && mesh.geometry
+        ? (mesh.geometry as { uniqueId?: number }).uniqueId ?? "geometry"
+        : "none";
+      return [
+        mesh.uniqueId,
+        geometryId,
+        mesh.getTotalVertices(),
+        mesh.getTotalIndices(),
+        mesh.computeWorldMatrix(true).asArray().map(formatMeasurementSnapSignatureNumber).join(","),
+      ].join(":");
+    }).join("|");
+  }
+
   private getMeasurementTargetMeshes(target = this.measurementTargetNode): AbstractMesh[] {
     if (!this.rootMesh || !target || isBabylonNodeDisposed(target)) return [];
     return this.getRenderableMeshes(this.rootMesh)
@@ -2333,6 +2356,10 @@ export class BabylonModelPreview implements WorkbenchPreview {
   }
 }
 
+function formatMeasurementSnapSignatureNumber(value: number): string {
+  return Number.isFinite(value) ? value.toPrecision(10) : String(value);
+}
+
 export function createBabylonModelPreview(canvas: HTMLCanvasElement): WorkbenchPreview {
   return new BabylonModelPreview(canvas);
 }

src/render/three/scene.ts

@@ -302,6 +302,7 @@ export class ThreeModelPreview implements WorkbenchPreview {
   private measurementTargetHelper: BoxHelper | null = null;
   private measurementSnapInputCache: MeasurementGeometrySnapInput | null = null;
   private measurementSnapInputCacheTarget: Object3D | null = null;
+  private measurementSnapInputCacheSignature: string | null = null;
   private measurementSnapKind: MeasurementSnapKind | null = null;
   private readonly measurementObservers = new Set<() => void>();
   private pendingPoint: Vector3 | null = null;
@@ -2648,6 +2649,7 @@ export class ThreeModelPreview implements WorkbenchPreview {
   private invalidateMeasurementSnapInputCache(): void {
     this.measurementSnapInputCache = null;
     this.measurementSnapInputCacheTarget = null;
+    this.measurementSnapInputCacheSignature = null;
   }
 
   private setMeasurementSnapKind(kind: MeasurementSnapKind | null, notify = true): void {
@@ -2712,11 +2714,16 @@ export class ThreeModelPreview implements WorkbenchPreview {
   private createMeasurementGeometrySnapInput(): MeasurementGeometrySnapInput | null {
     const target = this.measurementTargetObject;
     if (!target || !this.isObjectInLoadedRoot(target)) return null;
-    if (this.measurementSnapInputCache && this.measurementSnapInputCacheTarget === target) {
-      return this.measurementSnapInputCache;
-    }
     const renderables = this.getMeasurementTargetRenderables();
     if (renderables.length === 0) return null;
+    const signature = this.createMeasurementSnapInputSignature(renderables);
+    if (
+      this.measurementSnapInputCache &&
+      this.measurementSnapInputCacheTarget === target &&
+      this.measurementSnapInputCacheSignature === signature
+    ) {
+      return this.measurementSnapInputCache;
+    }
     const vertices: MeasurementSnapVertexCandidate[] = [];
     const edges: MeasurementSnapEdgeCandidate[] = [];
     const targetId = `three:${target.id}`;
@@ -2749,9 +2756,29 @@ export class ThreeModelPreview implements WorkbenchPreview {
     };
     this.measurementSnapInputCache = input;
     this.measurementSnapInputCacheTarget = target;
+    this.measurementSnapInputCacheSignature = signature;
     return input;
   }
 
+  private createMeasurementSnapInputSignature(renderables: readonly ThreeRenderableObject[]): string {
+    return renderables.map((object) => {
+      const geometry = object.geometry;
+      const position = geometry.getAttribute("position");
+      const index = geometry.getIndex();
+      const positionVersion = position && "version" in position ? (position as { version?: number }).version ?? 0 : 0;
+      object.updateWorldMatrix(true, false);
+      return [
+        object.id,
+        geometry.id,
+        position?.count ?? 0,
+        positionVersion,
+        index?.count ?? 0,
+        index?.version ?? 0,
+        object.matrixWorld.elements.map(formatMeasurementSnapSignatureNumber).join(","),
+      ].join(":");
+    }).join("|");
+  }
+
   private getMeasurementTargetRenderables(): ThreeRenderableObject[] {
     const target = this.measurementTargetObject;
     if (!this.rootObject || !target || !this.isObjectInLoadedRoot(target)) return [];
@@ -3092,6 +3119,10 @@ export class ThreeModelPreview implements WorkbenchPreview {
 
 }
 
+function formatMeasurementSnapSignatureNumber(value: number): string {
+  return Number.isFinite(value) ? value.toPrecision(10) : String(value);
+}
+
 export function createThreeModelPreview(canvas: HTMLCanvasElement): WorkbenchPreview {
   return new ThreeModelPreview(canvas);
 }