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  "contentMarkdown": "# OnProcessShader回调方法，为什么同一个shader会多次回调此方法？\n\n> [!note] 我的 UWA 问答\n> 本文收录我在 UWA 问答发表的公开回答。问题内容归原提问者；回答保留当时语境，技术结论可能受 Unity 版本、平台和项目条件限制。\n\n## 问题\n\nunity2018.4.36f1 在打安卓包时，发现OnProcessShader回调方法，同一个shader会被回调多次。\n\n- 提问者：龙少\n- 提问时间：2021-08-11 18:51:17\n\n## 我的回答\n\n简单地理解，OnProcessShader并不是一个“Shader资源“调用一次，而是一个 ”shader snippet“ 调用一次。官网上的说法：Implement this interface to receive a callback before a shader snippet is compiled.\n\n从这个函数的参数也可以看得出来，函数的一次调用，对应的是一个 Shader 的 一个 ShaderSnippetData。\n\n```\nOnProcessShader( Shader shader, ShaderSnippetData snippet, IList<ShaderCompilerData> data )\n```\n\n###\n\n至于要理解清楚的话，这个问题本质就是概念的定义与理解问题了。\n\n而对于 ”snippet“ 的定义，Unity官网的定义其实也有点矛盾，官方文档的说法与OnProcessShader函数用的概念是不一致的。\n\n比如官方文档表示：An HLSL snippet must contain at least a vertex program and a fragment program. 也就是说：一个snippet至少包含一个 vertex program和一个fragment program。\n\n(https://docs.unity3d.com/Manual/SL-PragmaDirectives.html)\n\n而OnProcessShader函数的介绍文档中表示：Shader snippet: The HLSL input code with dependencies for a single shader stage.  也就是说：一个snippet 对应的就是一个stage（vertex, fragment等等）\n\n(https://blog.unity.com/technology/stripping-scriptable-shader-variants)\n\n- 回答时间：2021-08-11 20:52:36\n- 最后更新：2021-08-11 20:53:17\n- 采纳状态：未采纳\n\n## 来源与关系\n\n- 上位集合：[[10-计算机、信息技术与工程/05-游戏图形与运行时/我的UWA问答/我的UWA问答|我的 UWA 问答]]\n- UWA 标签：Shader\n- 原始问题：[OnProcessShader回调方法，为什么同一个shader会多次回调此方法？](https://answer.uwa4d.com/question/61133b258f8c83424167271d)\n- 源页最后更新：2021-08-17 19:30:29\n"
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