Changes

Co-authored-by: Reifonas <211114984+Reifonas@users.noreply.github.com>

src/components/three/SmartMeasure.ts

@@ -443,6 +443,16 @@ const _ab = new THREE.Vector3();
 const _ap = new THREE.Vector3();
 const _closest = new THREE.Vector3();
 
+function closestPointOnSegment3D(p: THREE.Vector3, a: THREE.Vector3, b: THREE.Vector3, target: THREE.Vector3): THREE.Vector3 {
+  _ab.subVectors(b, a);
+  _ap.subVectors(p, a);
+  const abLenSq = _ab.lengthSq();
+  if (abLenSq < 1e-6) return target.copy(a);
+
+  const t = THREE.MathUtils.clamp(_ap.dot(_ab) / abLenSq, 0, 1);
+  return target.copy(a).addScaledVector(_ab, t);
+}
+
 function pointToSegmentDistSq3D(p: THREE.Vector3, a: THREE.Vector3, b: THREE.Vector3): number {
   _ab.subVectors(b, a);
   _ap.subVectors(p, a);
@@ -503,7 +513,7 @@ export function findNearestEdgeSegment3D(
   mesh: THREE.Mesh,
   worldPoint: THREE.Vector3,
   thresholdMeters: number = 0.05
-): { midpoint: THREE.Vector3; lengthMM: number; a: THREE.Vector3; b: THREE.Vector3 } | null {
+): { midpoint: THREE.Vector3; snapPoint: THREE.Vector3; lengthMM: number; a: THREE.Vector3; b: THREE.Vector3 } | null {
   let edgeLines: THREE.LineSegments | null = null;
   mesh.children.forEach(c => {
     if (c.userData.__edgeLine && c instanceof THREE.LineSegments) {
@@ -529,6 +539,7 @@ export function findNearestEdgeSegment3D(
 
   let bestDistSq = Infinity;
   let bestIndex = -1;
+  const bestClosestLocal = new THREE.Vector3();
   const thresholdSq = thresholdMeters * thresholdMeters;
 
   const segCount = posAttr.count / 2;
@@ -539,11 +550,13 @@ export function findNearestEdgeSegment3D(
     aLocal.fromBufferAttribute(posAttr, i * 2);
     bLocal.fromBufferAttribute(posAttr, i * 2 + 1);
 
-    const distSq = pointToSegmentDistSq3D(localPoint, aLocal, bLocal);
+    closestPointOnSegment3D(localPoint, aLocal, bLocal, _closest);
+    const distSq = localPoint.distanceToSquared(_closest);
 
     if (distSq < bestDistSq) {
       bestDistSq = distSq;
       bestIndex = i;
+      bestClosestLocal.copy(_closest);
     }
   }
 
@@ -551,8 +564,9 @@ export function findNearestEdgeSegment3D(
     const a = new THREE.Vector3().fromBufferAttribute(posAttr, bestIndex * 2).applyMatrix4(matrix);
     const b = new THREE.Vector3().fromBufferAttribute(posAttr, bestIndex * 2 + 1).applyMatrix4(matrix);
     const midpoint = a.clone().add(b).multiplyScalar(0.5);
+    const snapPoint = bestClosestLocal.clone().applyMatrix4(matrix);
     const lengthMM = a.distanceTo(b) * 1000;
-    return { midpoint, lengthMM, a, b };
+    return { midpoint, snapPoint, lengthMM, a, b };
   }
   return null;
 }
@@ -652,6 +666,6 @@ export function resolveSnap3D(
   const v = findNearestVertex3D(mesh, hitPoint, vertexThresholdMeters);
   if (v) return { point: v, type: 'vertex' };
   const e = findNearestEdgeSegment3D(mesh, hitPoint, edgeThresholdMeters);
-  if (e) return { point: e.midpoint, type: 'edge' };
+  if (e) return { point: e.snapPoint, type: 'edge' };
   return { point: hitPoint.clone(), type: 'surface' };
 }