Version: Unity 6 (6000.0)
Language : English
Include another HLSL file in a shader
Writing shaders for different graphics APIs

Pass information to the shader compiler in HLSL

In HLSL, you can use the following types of preprocessor directive to provide information to the shaderA program that runs on the GPU. More info
See in Glossary
compiler:

  • #pragma
  • #define_for_platform_compiler

Pragma directives

#pragma directives provide additional information to the shader compiler that isn’t covered by other types of preprocessor directive.

You can put #pragma directives anywhere in your HLSL code, but it is a common convention to put them at the start, like this:

#pragma target 3.0
#pragma exclude_renderers vulkan
#pragma vertex vert
#pragma fragment frag

// The rest of your HLSL code goes here

Limitations

There are some limitations around the use of #pragma directives:

  • You can use #pragmadirectives inside conditional (#if) directives if the expression depends only on:
    • Any custom #define directives in your own code
    • The following platform keywords: SHADER_API_MOBILE, SHADER_API_DESKTOP, UNITY_NO_RGBM, UNITY_USE_NATIVE_HDR, UNITY_FRAMEBUFFER_FETCH_AVAILABLE, UNITY_NO_CUBEMAP_ARRAY
    • The UNITY_VERSION macro
  • You can only use Unity-specific #pragma directives in .shader files, and in files that you include with the #include_with_pragmas directive. Unity does not support them in files that you include with the #include directive; the compiler ignores them.
  • You can only use standard HLSL #pragma directives in files that you include with the #include directive. Unity does not support them in .shader files, or in files that you include with an #include_with_pragmas directive; the compiler ignores them.

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.

Use a define_for_platform_compiler directive

Use a #define_for_platform_compiler directive in your shader code to send a #define directive to the shader compiler.

For example, #define_for_platform_compiler EXAMPLE_SYMBOL sends a #define EXAMPLE_SYMBOL directive to the shader compiler that defines a symbol called EXAMPLE_SYMBOL. Refer to external shader compiler documentation, for example Microsoft’s documentation on the FXC compiler, for more information about symbols that shader compilers use.

The Unity preprocessor doesn’t use symbols you define with #define_for_platform_compiler, so you can’t use the symbols in your own shader code. For example, in the above example, if you add shader code inside an #if (EXAMPLE_SYMBOL) statement, the code won’t run.

Additional resources

Include another HLSL file in a shader
Writing shaders for different graphics APIs