Got a bit further

src/Editor/Asset/MaterialLoader.cpp

@@ -17,7 +17,7 @@ MaterialLoader::MaterialLoader(Gfx::PGraphics graphics)
 {
     OMaterialAsset placeholderAsset = new MaterialAsset();
     import(MaterialImportArgs{
-        .filePath = std::filesystem::absolute("./shaders/Placeholder.asset"),
+        .filePath = std::filesystem::absolute("./shaders/Placeholder.json"),
         .importPath = "",
         }, placeholderAsset);
     AssetRegistry::get().assetRoot->materials[""] = std::move(placeholderAsset);

src/Editor/Asset/MeshLoader.cpp

@@ -257,6 +257,7 @@ void MeshLoader::loadGlobalMeshes(const aiScene* scene, const Array<PMaterialAss
         globalMeshes[meshIndex]->id = id;
         globalMeshes[meshIndex]->referencedMaterial = materials[mesh->mMaterialIndex]->getMaterial()->instantiate();
         globalMeshes[meshIndex]->meshlets = std::move(meshlets);
+        globalMeshes[meshIndex]->vertexCount = mesh->mNumVertices;
     }
 }