Stretch a vessel to its beam only beside a reported length

A vessel drawn at its type's typical length keeps the model's proportions:
a reported beam alone would squeeze a 300 m container ship to that width.

src/data/fleetModels.js

@@ -343,18 +343,22 @@ export function aircraftModelSpec(set, { typeCode, type, category } = {}) {
  * @returns {object} {@link fleetModelSpec}
  */
 export function vesselModelSpec(set, { type, length, beam, name } = {}) {
+  // A beam counts only beside a reported length: a vessel drawn at its type's
+  // typical length keeps the model's proportions.
+  const reported = hullLength(length ?? undefined);
+  const hullWidth = reported === undefined ? undefined : (beam ?? undefined);
   const resolved = resolveVessel(
     set.types,
     aisShipTypeCode(type),
-    length ?? undefined,
-    beam ?? undefined,
+    reported,
+    hullWidth,
     name ?? undefined,
   );
   return specOf(
     set,
     resolved,
     (r) => ({ model: set.types.default_vessel, length: r.length }),
-    { beam: beam ?? undefined },
+    { beam: hullWidth },
   );
 }
 

src/data/fleetModels.test.mjs

@@ -291,6 +291,12 @@ test('vessel specs read AIS codes and text families, stretched to the reported b
   const [sx, sy, sz] = box.scaleXYZ;
   assert.ok(Math.abs(sy - 51 / catalog.container_ship.beam) < 1e-12);
   assert.ok(Math.abs(sz - (sx + sy) / 2) < 1e-12);
+  // A beam with no reported length: the type's typical length, in the model's
+  // own proportions, not a typical-length hull squeezed to that beam.
+  const unsized = vesselModelSpec(set, { type: '70', length: 0, beam: 14 });
+  assert.equal(unsized.model, 'container_ship');
+  const [ux, uy, uz] = unsized.scaleXYZ;
+  assert.ok(Math.abs(uy - ux) < 1e-12 && Math.abs(uz - ux) < 1e-12);
   assert.equal(vesselModelSpec(set, { type: 'Tug', length: 30 }).model, 'tug');
   assert.equal(vesselModelSpec(set, { type: '36' }).model, 'sailboat');
   // No type, no size: the generic vessel as built.