feat(preview): add low poly vehicle library

scripts/lib/vehicle-library.js

@@ -0,0 +1,49 @@
+"use strict";
+
+const fs = require("fs");
+const path = require("path");
+
+const VEHICLE_IDS = [
+  "car_a01_002",
+  "car_a02_002",
+  "car_a03_001",
+  "truck_a01_001",
+  "truck_a02_001",
+  "truck_a03_001",
+];
+const LIBRARY_ROOT = path.resolve(__dirname, "..", "..", "assets", "models", "custom", "lowpoly_cars");
+const TEXTURE_NAME = "color_512x512.jpg";
+const REVERSED_MODEL_IDS = new Set(["truck_a03_001"]);
+
+function writePreviewVehicleLibrary(outDir, fileStem) {
+  const textureOutput = `${fileStem}-vehicle-texture.jpg`;
+  fs.mkdirSync(outDir, { recursive: true });
+  fs.copyFileSync(path.join(LIBRARY_ROOT, "textures", TEXTURE_NAME), path.join(outDir, textureOutput));
+  return VEHICLE_IDS.map((id) => {
+    const modelName = `${fileStem}-vehicle-${id}.gltf`;
+    const binName = `${fileStem}-vehicle-${id}.bin`;
+    const sourceDir = path.join(LIBRARY_ROOT, id);
+    const gltf = JSON.parse(fs.readFileSync(path.join(sourceDir, "model.gltf"), "utf8"));
+    for (const image of gltf.images || []) image.uri = textureOutput;
+    for (const buffer of gltf.buffers || []) buffer.uri = binName;
+    if (REVERSED_MODEL_IDS.has(id)) {
+      // The source's longitudinal PCA axis points rearward for this truck.
+      for (const node of gltf.nodes || []) node.rotation = [0, 1, 0, 0];
+    }
+    for (const material of gltf.materials || []) {
+      const pbr = material.pbrMetallicRoughness || (material.pbrMetallicRoughness = {});
+      // Match the Cesium foliage profile: lift albedo first, then use the
+      // texture itself as a modest shadow-side floor.
+      pbr.baseColorFactor = [2.1, 2.1, 2.1, 1];
+      if (pbr.baseColorTexture) {
+        material.emissiveTexture = { ...pbr.baseColorTexture };
+        material.emissiveFactor = [0.25, 0.25, 0.25];
+      }
+    }
+    fs.writeFileSync(path.join(outDir, modelName), `${JSON.stringify(gltf, null, 2)}\n`);
+    fs.copyFileSync(path.join(sourceDir, "model.bin"), path.join(outDir, binName));
+    return modelName;
+  });
+}
+
+module.exports = { VEHICLE_IDS, REVERSED_MODEL_IDS, writePreviewVehicleLibrary };