Surface-to-point couplings (KOF-208, part 2): model-side pipeline

web/package.json

@@ -17,7 +17,7 @@
     "examples:generate": "bun ../examples/web-examples/generate.mjs",
     "examples:generate-crane-shell": "bun ../examples/web-examples/generate-crane-shell.mjs",
     "examples:generate-plate-hole-shell": "bun ../examples/web-examples/generate-plate-hole-shell.mjs",
-    "test": "bun ../examples/validation/run.mjs && bun ../examples/validation/dof-constraint.test.mjs && bun ../examples/validation/prescribed-displacement.test.mjs && bun tests/test_wall_bracket.mjs 20.0 && bun tests/test_multibody.mjs && bun tests/test_tie.mjs && bun tests/test_coupling.mjs && bun tests/test_face_pick.mjs && bun tests/test_edge_pick.mjs && bun tests/test_moment_load.mjs && bun tests/test_shellize_mpc.mjs && bun tests/test_body_highlight.mjs && bun tests/test_midsurface_junction.mjs && bun tests/test_coupled_materials.mjs && playwright test",
+    "test": "bun ../examples/validation/run.mjs && bun ../examples/validation/dof-constraint.test.mjs && bun ../examples/validation/prescribed-displacement.test.mjs && bun tests/test_wall_bracket.mjs 20.0 && bun tests/test_multibody.mjs && bun tests/test_tie.mjs && bun tests/test_coupling.mjs && bun tests/test_reference_point.mjs && bun tests/test_face_pick.mjs && bun tests/test_edge_pick.mjs && bun tests/test_moment_load.mjs && bun tests/test_shellize_mpc.mjs && bun tests/test_body_highlight.mjs && bun tests/test_midsurface_junction.mjs && bun tests/test_coupled_materials.mjs && playwright test",
     "test:coverage": "rm -rf .nyc_output coverage && COVERAGE=1 playwright test && bun run coverage:report",
     "coverage:report": "nyc report && bun scripts/coverage-dead-code.ts",
     "test:ui": "playwright test --ui",

web/src/components/panel/BcLoadFormControls.tsx

@@ -2,8 +2,11 @@
 // SPDX-License-Identifier: AGPL-3.0-or-later
 
 import type {
+  CouplingKind,
   FaceSelection,
   LoadKind,
+  PickGeometry,
+  ReferencePointOption,
   TieExtent,
 } from "../../store/modelStore";
 import {
@@ -14,50 +17,62 @@ import {
 } from "./bcFormUtils";
 import styles from "./LeftPanel.module.css";
 
-// Face / Edge picker for shell models: a flat shell sheet is one face-pick
-// region, so grabbing its rim (an edge load or supported-edge BC) needs edge
-// picking (#386). Offered only when the model has CTRIA3 elements.
+const GEOMETRY_LABEL: Record<PickGeometry, string> = {
+  face: "Face",
+  edge: "Edge",
+  point: "Point",
+};
+
+// What a click selects. `options` is explicit because not every geometry suits
+// every model or every condition: edge picking only means something on a shell
+// (a closed solid boundary has no boundary polyline to walk), and a point pick
+// is not offered where a single node would be the wrong thing to define.
+// Rendered only when there is a genuine choice to make.
 export function PickGeometryToggle({
   value,
+  options,
   onChange,
 }: {
-  value: "face" | "edge";
-  onChange(geometry: "face" | "edge"): void;
+  value: PickGeometry;
+  options: PickGeometry[];
+  onChange(geometry: PickGeometry): void;
 }) {
+  if (options.length < 2) return null;
   return (
     <div className={styles.segToggle} role="group" aria-label="Pick geometry">
-      {(["face", "edge"] as const).map((geometry) => (
+      {options.map((geometry) => (
         <button
           key={geometry}
           type="button"
+          data-testid={`pick-geometry-${geometry}`}
           className={`${styles.segBtn} ${value === geometry ? styles.segBtnActive : ""}`}
           aria-pressed={value === geometry}
           onClick={() => onChange(geometry)}
         >
-          {geometry === "face" ? "Face" : "Edge"}
+          {GEOMETRY_LABEL[geometry]}
         </button>
       ))}
     </div>
   );
 }
 
+const PICK_HINT: Record<PickGeometry, string> = {
+  face: "Click a face in the 3D viewport",
+  edge: "Click near a mesh edge in the 3D viewport",
+  point: "Click near a mesh node in the 3D viewport",
+};
+
 export function PickedFaceList({
   faces,
   onRemove,
   geometry = "face",
 }: {
   faces: FaceSelection[];
   onRemove(index: number): void;
-  geometry?: "face" | "edge";
+  geometry?: PickGeometry;
 }) {
   if (faces.length === 0) {
-    return (
-      <div className={styles.pickHint}>
-        {geometry === "edge"
-          ? "Click near a mesh edge in the 3D viewport"
-          : "Click a face in the 3D viewport"}
-      </div>
-    );
+    return <div className={styles.pickHint}>{PICK_HINT[geometry]}</div>;
   }
   return (
     <div>
@@ -229,3 +244,92 @@ export function DofCheckboxes({
     </div>
   );
 }
+
+// How a surface-to-point coupling ties its surface to its reference point. The
+// two kinds are not interchangeable — see lib/coupling.ts — so the difference
+// is spelled out under the select rather than left to the two words.
+export function CouplingKindSelect({
+  value,
+  onChange,
+}: {
+  value: CouplingKind;
+  onChange(kind: CouplingKind): void;
+}) {
+  return (
+    <>
+      <div className={styles.formRow}>
+        <span className={styles.formLabel}>Kind</span>
+        <select
+          className={styles.formSelect}
+          data-testid="coupling-kind"
+          value={value}
+          onChange={(e) => onChange(e.target.value as CouplingKind)}
+        >
+          <option value="distributing">Distributing (RBE3)</option>
+          <option value="kinematic">Kinematic (RBE2)</option>
+        </select>
+      </div>
+      <div className={styles.pickNote}>
+        {value === "distributing"
+          ? "the surface stays flexible and the point follows it — the point can be loaded, but not fixed"
+          : "the surface follows the point rigidly — the point can be fixed, loaded or coupled onward"}
+      </div>
+    </>
+  );
+}
+
+// Where the reference point sits: one of the positions derived from the picked
+// surface (its centre, and the two ends of its axis when it is a cylinder), or
+// coordinates typed in. Choosing a derived position fills the coordinate boxes,
+// which stay editable — the derived positions are a starting point, not a
+// constraint (KOF-208).
+export function ReferencePointInputs({
+  options,
+  coords,
+  onCoordChange,
+  onPickOption,
+}: {
+  options: ReferencePointOption[];
+  coords: [string, string, string];
+  onCoordChange(index: number, value: string): void;
+  onPickOption(option: ReferencePointOption): void;
+}) {
+  return (
+    <>
+      {options.length > 0 && (
+        <div className={styles.formRow}>
+          <span className={styles.formLabel}>Place at</span>
+          <select
+            className={styles.formSelect}
+            data-testid="coupling-place-at"
+            value=""
+            onChange={(e) => {
+              const option = options[Number(e.target.value)];
+              if (option) onPickOption(option);
+            }}
+          >
+            <option value="">Custom coordinates</option>
+            {options.map((option, i) => (
+              <option key={option.label} value={i}>
+                {option.label}
+              </option>
+            ))}
+          </select>
+        </div>
+      )}
+      {["X", "Y", "Z"].map((axis, i) => (
+        <div className={styles.formRow} key={axis}>
+          <span className={styles.formLabel}>{axis} (mm)</span>
+          <input
+            className={styles.formInput}
+            data-testid={`coupling-point-${axis.toLowerCase()}`}
+            type="number"
+            step="0.1"
+            value={coords[i]}
+            onChange={(e) => onCoordChange(i, e.target.value)}
+          />
+        </div>
+      ))}
+    </>
+  );
+}

web/src/components/panel/BcSection.tsx

@@ -26,6 +26,7 @@ export function BcSection({ onError }: { onError(msg: string | null): void }) {
   const hasShells = useModelStore((s) =>
     s.elements.some((el) => el.type === "CTRIA3"),
   );
+  const couplingGroups = useModelStore((s) => s.couplingGroups);
   const createBcGroup = useModelStore((s) => s.createBcGroup);
   const addFaceToBcGroup = useModelStore((s) => s.addFaceToBcGroup);
   const removeFaceFromBcGroup = useModelStore((s) => s.removeFaceFromBcGroup);
@@ -51,6 +52,15 @@ export function BcSection({ onError }: { onError(msg: string | null): void }) {
     false,
   ]);
   const [bcValue, setBcValue] = useState("0");
+  // Whether the pick has landed on a coupling's reference point — clicked in
+  // the viewport like anything else. Such a point carries six real DOFs
+  // (shell_core gives a coupling reference its rotations), so the rotational
+  // boxes become meaningful: fixing them is how a bolted or welded connection
+  // is restrained without clamping every node of the bore.
+  const refPoints = new Set(couplingGroups.map((c) => c.refNodeId));
+  const pickedReferencePoint = allPickedFaces.some((face) =>
+    face.nodeIds.every((id) => refPoints.has(id)),
+  );
 
   const targetBcGroup =
     pickTargetGroupId !== null
@@ -63,7 +73,7 @@ export function BcSection({ onError }: { onError(msg: string | null): void }) {
       allPickedFaces,
       // eslint-disable-next-line kofem/no-silent-fallback -- numbering offset for the new entries; a pick with no target group starts a fresh group, which has 0 faces
       targetBcGroup?.faces.length ?? 0,
-      pickGeometry === "edge" ? "Edge" : "Face",
+      pickGeometry,
     );
     if (targetBcGroup) {
       for (const faceEntry of faceEntries) {
@@ -109,12 +119,16 @@ export function BcSection({ onError }: { onError(msg: string | null): void }) {
             </button>
           </div>
 
-          {hasShells && (
-            <PickGeometryToggle
-              value={pickGeometry}
-              onChange={setPickGeometry}
-            />
-          )}
+          {/* Point picking is offered so a coupling's REFERENCE POINT can be
+              fixed — clicked in the viewport like any other selection, which is
+              the only way to restrain a bolted hole without clamping every node
+              of its bore. It also allows a single mesh node, which is a
+              legitimate way to remove a rigid-body mode. */}
+          <PickGeometryToggle
+            value={pickGeometry}
+            options={hasShells ? ["face", "edge", "point"] : ["face", "point"]}
+            onChange={setPickGeometry}
+          />
 
           <PickedFaceList
             faces={allPickedFaces}
@@ -124,9 +138,11 @@ export function BcSection({ onError }: { onError(msg: string | null): void }) {
 
           {allPickedFaces.length > 0 && !targetBcGroup && (
             <>
+              {/* A reference point carries six DOFs whichever elements the
+                  model has, so Rx/Ry/Rz appear as soon as one is picked. */}
               <DofCheckboxes
                 checkedDofs={checkedDofs}
-                showRotations={hasShells}
+                showRotations={hasShells || pickedReferencePoint}
                 onToggle={(index) =>
                   setCheckedDofs((prev) =>
                     prev.map((checked, i) =>

web/src/components/panel/BoundaryConditionsPanel.tsx

@@ -6,6 +6,7 @@ import { useModelStore } from "../../store/modelStore";
 import { BcSection } from "./BcSection";
 import { LoadSection } from "./LoadSection";
 import { TieSection } from "./TieSection";
+import { CouplingSection } from "./CouplingSection";
 import styles from "./LeftPanel.module.css";
 
 export function BoundaryConditionsPanel() {
@@ -33,6 +34,7 @@ export function BoundaryConditionsPanel() {
             <BcSection onError={setError} />
             <LoadSection onError={setError} />
             <TieSection onError={setError} />
+            <CouplingSection onError={setError} />
           </>
         )}
       </div>