Pass information to shader compilers in HLSL

To pass information to the shader compilers in High-Level Shader Language (HLSL), use one of the following directives:

• The standard HLSL #define directive.
• The standard HLSL #pragma directive, to pass standard HLSL or Unity-specific directives.
• The Unity #define_for_platform_compiler directive.

Add a #define directive

Unity supports the standard HLSL #define directive. For more information, see [#define directive](https://learn.microsoft.com/en-us/windows/win32/direct3dhlsl/dx-graphics-hlsl-appendix-pre-define) in the Microsoft HLSL documentation. For example:

Shader "Custom/ExampleShader"
{
    SubShader
    {
        Pass
        {
            HLSLPROGRAM

            // Define a symbol called EXAMPLE_SYMBOL
            #define EXAMPLE_SYMBOL

            // Add your shader code here

            ENDHLSL
        }
    }
}

Add a #pragma directive

Use a #pragma directive to do the following:

• Pass Unity-specific directives, for example to add shader keywords or target specific graphics APIs. For more information, refer to HLSL pragma directives reference.
• Pass standard HLSL directives. For more information, refer to [#pragma directive](https://learn.microsoft.com/en-us/windows/win32/direct3dhlsl/dx-graphics-hlsl-appendix-pre-pragma) in the Microsoft HLSL documentation.

Add a #pragma statement anywhere in your HLSLPROGRAM, but usually at the start. For example:

Shader "Custom/ExampleShader"
{
    SubShader
    {
        Pass
        {
            HLSLPROGRAM

            // Target shader model 3.0
            #pragma target 3.0

            // Compile this shader only for Direct3D 11 and OpenGL Core
            #pragma only_renderers d3d11 glcore

            // Add your shader code here

            ENDHLSL
        }
    }
}

Limitations

Unity recognizes #pragma directives only in the following contexts:

• Unity-specific directives: In .shader files, or files you include with the #include_with_pragmas directive.
• Standard HLSL directives: In files you include with the #include directive.

Unity ignores #pragma directives outside these contexts.

Note: If a shader file uses #include to import a file that contains an #include_with_pragmas directive, Unity ignores the #pragma directives in the file the #include_with_pragmas directive references.

If you put a #pragma directive inside an #if statement, the condition must depend on one of the following:

• A custom symbol you define in a #define directive.
• The SHADER_API_MOBILE or SHADER_API_DESKTOP platform macros for branching based on the target platform.
• The UNITY_NO_RGBM or UNITY_FRAMEBUFFER_FETCH_AVAILABLE macros for branching based on platform features.
• The UNITY_USE_NATIVE_HDR macro.
• The UNITY_NO_CUBEMAP_ARRAY macro.
• The UNITY_VERSION macro for branching based on Unity version.

Add a #define_for_platform_compiler directive

To pass information to the platform-specific shader compiler, for example the FXC compiler if you target a platform that uses DirectX, add a #define_for_platform_compiler directive. For example:

Shader "Custom/ExampleShader"
{
    SubShader
    {
        Pass
        {
            HLSLPROGRAM

            // Define a symbol called EXAMPLE_SYMBOL for the platform-specific shader compiler
            #define_for_platform_compiler EXAMPLE_SYMBOL

            // Add your shader code here

            ENDHLSL
        }
    }
}

The directive sends a #define directive to the platform-specific shader compiler. For example, #define_for_platform_compiler EXAMPLE_SYMBOL sends a #define EXAMPLE_SYMBOL directive to the shader compiler.

The Unity preprocessor doesn’t use symbols you define with #define_for_platform_compiler. If you use the symbols inside conditional statements in your own shader code, the code won’t run.

Additional resources

• Shader compilation
• HLSL pragma directives reference
• HLSL pragma target command reference
• HLSL pragma require command reference
• HLSL documentation on the Microsoft website