当使用Assimp库加载GLTF模型时，有时会发现模型的网格不是按预期缩放的。这通常是由于模型导出时使用了不同的单位（例如cm，m或mm）导致的。

为了解决这个问题，可以通过以下代码来手动调整模型的比例：

// 载入模型
Assimp::Importer importer;
const aiScene* scene = importer.ReadFile("model.gltf", aiProcess_ValidateDataStructure);

// 获取根节点的变换
aiMatrix4x4 rootTransform = scene->mRootNode->mTransformation;

// 获取每个子节点网格的变换
for (unsigned int i = 0; i < scene->mNumMeshes; ++i)
{
    aiMesh* mesh = scene->mMeshes[i];
    aiMaterial* material = scene->mMaterials[mesh->mMaterialIndex];
    aiString matName;
    material->Get(AI_MATKEY_NAME, matName);

    aiMatrix4x4 meshTransform = aiMatrix4x4();
    aiNode* node = scene->mRootNode->FindNode(mesh->mName);
    while (node)
    {
        meshTransform = node->mTransformation * meshTransform;
        node = node->mParent;
    }

    // 计算缩放比例
    aiVector3D scale;
    meshTransform.Decompose(scale, aiQuaternion(), aiVector3D());
    float scaleValue = (scale.x + scale.y + scale.z) / 3.0f;

    // 将模型缩放到所需的大小
    meshTransform = aiMatrix4x4::Scaling(aiVector3D(1.0f / scaleValue));
    meshTransform = meshTransform * rootTransform;

    // 将网格变换应用到顶点中
    for (unsigned int j = 0; j < mesh->mNumVertices; ++j)
    {
        aiVector3D& vertex = mesh->mVertices[j];
        aiVector3D transformedVertex = meshTransform * aiVector4D(vertex.x, vertex.y,