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 shaderA program that runs on the GPU. More info
  See in Glossary 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 terrainThe landscape in your scene. A Terrain GameObject adds a large flat plane to your scene and you can use the Terrain’s Inspector window to create a detailed landscape. More info
  See in Glossary 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/CGIncludes/UnityCG.cginc on Windows, /Applications/Unity/Unity.app/Contents/CGIncludes/UnityCG.cginc on Mac), if you want to take a look at what exactly is done in any of the helper code.