Import a file from the shader library in the Built-In Render Pipeline

Unity contains several files that can be used by your shader programs to bring in predefined variables and helper functions. This is done by the standard #include directive, e.g.:

SubShader {
    Pass {
        HLSLPROGRAM

        #include "UnityCG.cginc"

        ENDHLSL
    }
}

Shader include files in Unity are with .cginc extension, and the built-in ones are:

• HLSLSupport.cginc: Declares various preprocessor macros to aid in multi-platform shader development. Unity automatically includes this file if you use CGPROGRAM. For more information, refer to Shader code blocks in ShaderLab reference.
• UnityShaderVariables.cginc: Declares various built-in global variables that are commonly used in shaders. Unity automatically includes this file if you use CGPROGRAM. For more information, refer to Shader code blocks in ShaderLab reference.
• UnityCG.cginc: Commonly used built-in helper functions and data structures.
• AutoLight.cginc: Lighting and shadowing functionality, for example surface shadersA streamlined way of writing shaders for the Built-in Render Pipeline. More info
  See in Glossary use this file internally.
• Lighting.cginc: Standard surface shader lighting models. Unity automatically includes this file if your write surface shaders.
• TerrainEngine.cginc: Helper functions for terrain and vegetation shaders.

Note: Although shader library files have a .cginc file extension, they’re written in HLSL rather than CG.

These files are found inside Unity application ({unity install path}/Data/Resources/CGIncludes/UnityCG.cginc on Windows, /Applications/Unity/Unity.app/Contents/Resources/CGIncludes/UnityCG.cginc on Mac), if you want to take a look at what exactly is done in any of the helper code.