feat(view): round bar bends at the centre-line radius; bend factors as inputs on ③

Bars drawn through several points are one tube each, with every bend rounded by R·tan(φ/2) at the centre-line radius
(inner factor × d + d/2). The inside-radius factors (D16 and below, D19–D25, D29–D35, D38 and above) are inputs in 공통
설정, with KDS-based defaults 2 / 3 / 4 / 5. The size-class limits sit in one place (SIZE_CLASS), which also fixes
D25 (25.4) being read as the D29–D35 class in hookLength. The helper bendDeduction gives the centre-line deduction for
the length option, which is not yet applied to the 철근표 lengths.

Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com>

src/view/rebar3d.ts

@@ -5,7 +5,7 @@ import { bottomPiece, MAIN, widthLayout } from '../core/rebar/coping-main';
 import { C14_INSET, c14Bars, CAP, COPING_REBAR, SHEAR_LOOP_STEP, shearBars, shearBarsMulti, shearUHeight, copingSideBars, SIDE_HOOK_LEG, stairBars, undersideAt } from '../core/rebar/coping';
 import { columnRebar, COLUMN_P1 } from '../core/rebar/column';
 import { barsAcross, BLOCK_REBAR } from '../core/rebar/bearing-block';
-import { DEFAULT_MATERIAL, FckByMember, hookLength, Material, materialFor, NOMINAL_DIAMETER } from '../core/rebar/common';
+import { bendRadius, DEFAULT_MATERIAL, FckByMember, hookLength, Material, materialFor, NOMINAL_DIAMETER } from '../core/rebar/common';
 import { diameterGroupIndex, DIAMETER_GROUPS, memberOfBar, type RebarMemberKey } from '../core/rebar/color';
 import { stretchMatrix } from './scene';
 
@@ -62,6 +62,50 @@ export function buildRebar3D(m: PierModel, common: Material = DEFAULT_MATERIAL,
   const B = m.copingB;
   const straight = m.kink === null;
 
+  /**
+   * A bar through several points as one tube, each bend rounded to its centre-line radius (수정 2026-10-23).
+   * A bend of deflection φ is cut back by t = R·tan(φ/2) on both sides and joined by a quadratic curve through the corner.
+   */
+  const addPath = (name: string, k: number, pts: [number, number, number][], dMm: number, color: number) => {
+    if (pts.length < 2) return;
+    const R = mm(bendRadius(dMm, common.bend));
+    const pv = pts.map((p) => new THREE.Vector3(p[0], p[1], p[2]));
+    const path = new THREE.CurvePath<THREE.Vector3>();
+    let cur = pv[0].clone();
+    for (let i = 1; i < pv.length - 1; i++) {
+      const prev = pv[i - 1];
+      const corner = pv[i];
+      const next = pv[i + 1];
+      const u = corner.clone().sub(prev);
+      const v = next.clone().sub(corner);
+      const lenIn = u.length();
+      const lenOut = v.length();
+      if (lenIn < 1e-9 || lenOut < 1e-9) continue;
+      u.normalize();
+      v.normalize();
+      const phi = Math.acos(Math.min(1, Math.max(-1, u.dot(v))));
+      // Cut back by the tangent length, never more than half of either adjacent piece.
+      const t = Math.min(R * Math.tan(phi / 2), lenIn / 2, lenOut / 2);
+      const a = corner.clone().addScaledVector(u, -t);
+      const b = corner.clone().addScaledVector(v, t);
+      if (a.distanceTo(cur) > 1e-9) path.add(new THREE.LineCurve3(cur, a));
+      path.add(new THREE.QuadraticBezierCurve3(a, corner, b));
+      cur = b;
+    }
+    const last = pv[pv.length - 1];
+    if (last.distanceTo(cur) > 1e-9) path.add(new THREE.LineCurve3(cur, last));
+    const segments = Math.min(400, Math.max(12, Math.round(path.getLength() * 100)));
+    const geo = new THREE.TubeGeometry(path, segments, mm(dMm) / 2, 6, false);
+    geo.applyMatrix4(Ms[k]);
+    const mat = new THREE.MeshStandardMaterial({ color: rebarColor(color), roughness: 0.45, metalness: 0.1 });
+    const mesh = new THREE.Mesh(geo, mat);
+    mesh.userData = { name, roleColor: color, dMm, member: memberOfBar(name) };
+    group.add(mesh);
+    const list = byName.get(name) ?? [];
+    list.push(mesh);
+    byName.set(name, list);
+  };
+
   const addBar = (name: string, k: number, a: [number, number, number], b: [number, number, number], dMm: number, color: number) => {
     const dir = new THREE.Vector3(b[0] - a[0], b[1] - a[1], b[2] - a[2]);
     const len = dir.length();
@@ -100,7 +144,7 @@ export function buildRebar3D(m: PierModel, common: Material = DEFAULT_MATERIAL,
           [L - xk, z, n],
           [L - xk, z - hookTop, n],
         ];
-        for (let s = 0; s + 1 < pts.length; s++) addBar(name, 0, pts[s], pts[s + 1], NOMINAL_DIAMETER.H29, COLOR.coping);
+        addPath(name, 0, pts, NOMINAL_DIAMETER.H29, COLOR.coping);
       });
     }
     // Bottom bars C7 / C8 (코핑철근.md §5.2–5.3): they follow the sloped underside, 127 above it, with a vertical leg up
@@ -119,7 +163,7 @@ export function buildRebar3D(m: PierModel, common: Material = DEFAULT_MATERIAL,
       const right = left.map(([x, y, zz]): [number, number, number] => [L - x, y, zz]);
       const name = j % 2 === 1 ? 'C7' : 'C8';
       for (const pts of [left, right]) {
-        for (let k = 0; k + 1 < pts.length; k++) addBar(name, 0, pts[k], pts[k + 1], NOMINAL_DIAMETER.H29, COLOR.coping);
+        addPath(name, 0, pts, NOMINAL_DIAMETER.H29, COLOR.coping);
       }
     });
     // Shear loops C9 / C10 / C11 and the gaps between columns: a closed U at each position.
@@ -323,7 +367,7 @@ export function buildRebar3D(m: PierModel, common: Material = DEFAULT_MATERIAL,
     const off = legOffsets();
     // One name, several cylinders: each segment of the path is one bar piece.
     const path = (name: string, pts: [number, number, number][], dMm: number) => {
-      for (let k = 0; k + 1 < pts.length; k++) addBar(name, 0, pts[k], pts[k + 1], dMm, COLOR.footing);
+      addPath(name, 0, pts, dMm, COLOR.footing);
     };
     // B1–B4: along s, at W position n. legTo (absolute EL, m) is where both ends turn up or down (§5.1); undefined = straight.
     const along = (name: string, n: number, y: number, legTo: number | undefined, dMm: number) => {
@@ -375,7 +419,7 @@ export function buildRebar3D(m: PierModel, common: Material = DEFAULT_MATERIAL,
 
     // B10-1 / B10-2 (§7) at each B10 level, B11 / B12 (§8) between them. Ends turn 90° inward (B10) or down (B11, B12).
     const polyline = (name: string, pts: [number, number, number][], dMm: number) => {
-      for (let k = 0; k + 1 < pts.length; k++) addBar(name, 0, pts[k], pts[k + 1], dMm, COLOR.footing);
+      addPath(name, 0, pts, dMm, COLOR.footing);
     };
     const hookB10 = mm(hookLength('main90', NOMINAL_DIAMETER.S19)); // 296
     const hookAsm = mm(Math.round(hookLength('main90', NOMINAL_DIAMETER.S16))); // 246