在 HLSLSupport.cginc 文件中定义了此宏：
#if defined(UNITY_COMPILER_HLSL) #define UNITY_INITIALIZE_OUTPUT(type,name) name = (type)0; #else #define UNITY_INITIALIZE_OUTPUT(type,name) #endif
只有在HLSL编译器编译时，它才工作，初始化name参数，否则编译器可能会报如下错误：
“Shader error in ‘Jie/Test‘: ‘vert‘: output parameter ‘o‘ not completely initialized at line 37”
ShaderLab 之 UNITY_INITIALIZE_OUTPUT
原文：http://www.cnblogs.com/jietian331/p/4118677.html