Changes

src/lib/generateDemoBeam.ts

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+import * as THREE from 'three';
+import { GLTFExporter } from 'three/examples/jsm/exporters/GLTFExporter.js';
+
+/**
+ * Generates a steel I-beam (IPE 200) as a GLB blob.
+ * Dimensions in meters (model is 1:1 scale, original units mm).
+ * IPE 200: h=200mm, b=100mm, tw=5.6mm, tf=8.5mm, length=1000mm
+ */
+export async function generateDemoBeamGLB(): Promise<{ blob: Blob; fileName: string; fileSize: number }> {
+  const scene = new THREE.Scene();
+
+  // IPE 200 dimensions in meters
+  const h = 0.200;    // height
+  const b = 0.100;    // flange width
+  const tw = 0.0056;  // web thickness
+  const tf = 0.0085;  // flange thickness
+  const L = 1.0;      // length (1000mm)
+
+  const material = new THREE.MeshStandardMaterial({
+    color: 0x8899aa,
+    metalness: 0.85,
+    roughness: 0.35,
+  });
+
+  // Web (vertical plate in the center)
+  const webHeight = h - 2 * tf;
+  const webGeo = new THREE.BoxGeometry(L, webHeight, tw);
+  const web = new THREE.Mesh(webGeo, material);
+  web.position.set(0, 0, 0);
+
+  // Top flange
+  const topFlangeGeo = new THREE.BoxGeometry(L, tf, b);
+  const topFlange = new THREE.Mesh(topFlangeGeo, material);
+  topFlange.position.set(0, (webHeight + tf) / 2, 0);
+
+  // Bottom flange
+  const bottomFlangeGeo = new THREE.BoxGeometry(L, tf, b);
+  const bottomFlange = new THREE.Mesh(bottomFlangeGeo, material);
+  bottomFlange.position.set(0, -(webHeight + tf) / 2, 0);
+
+  const group = new THREE.Group();
+  group.name = 'IPE200_Steel_Beam';
+  group.add(web, topFlange, bottomFlange);
+  scene.add(group);
+
+  // Export as GLB
+  const exporter = new GLTFExporter();
+  const glb = await new Promise<ArrayBuffer>((resolve, reject) => {
+    exporter.parse(
+      scene,
+      (result) => resolve(result as ArrayBuffer),
+      (error) => reject(error),
+      { binary: true }
+    );
+  });
+
+  const blob = new Blob([glb], { type: 'model/gltf-binary' });
+  return {
+    blob,
+    fileName: 'Demo_IPE200_1000mm.glb',
+    fileSize: blob.size,
+  };
+}