使用 spin-unity 3.8 时，您需要在 Inspector 的 Skeleton Data Modifiers 中的项目中的 _SkeletonData 资产中分配 BlendModeMaterialsAsset。 为此目的，您可以分配“默认 BlendModeMaterials”。

请参阅此处的文档（我们很抱歉，由于该功能在 spin-unity 4.0 和更新版本中已过时，因此仅翻译了部分内容）：
spine-unity 运行时文档: SkeletonData 修改器资产

When using spine-unity 3.8, you need to assign a BlendModeMaterialsAsset at the _SkeletonData asset in your project, in Skeleton Data Modifiers in the Inspector. There is Default BlendModeMaterials provided for this purpose that you can assign.

See the documentation here (we apologize that only part of it has been translated yet, due to the feature being obsolete in spine-unity 4.0 and newer versions):
spine-unity 运行时文档: SkeletonData 修改器资产