Make shader behavior conditional

To mark parts of your shaderA program that runs on the GPU. More info
See in Glossary code conditional based on whether you enable or disable a shader keyword in a set, use an HLSL if statement.

For example:

#pragma multi_compile QUALITY_LOW QUALITY_MED QUALITY_HIGH

if (QUALITY_LOW)
{
    // code for low quality setting
}
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You can enable and disable keywords using the Inspector or C# scripting.

What Unity does with your shader code depends on which shader directive you use.

Unity creates separate shader variantsA verion of a shader program that Unity generates according to a specific combination of shader keywords and their status. A Shader object can contain multiple shader variants. More info
See in Glossary for each keyword state. Each variant contains the code from an if branch for that keyword. When you enable a keyword, Unity sends the matching variant to your GPU. This is static branching.

Refer to Conditionals in shaders for more information about when to use which shader directive.

Branch when all keywords in a set are disabled

To execute code when all keywords in a set are disabled, Unity must create an additional shader variant for that state.

If you use shader_feature to create a single keyword, Unity automatically creates an additional variant. For example:

// Creates a variant for when FEATURE_1_ON is enabled, and another for when FEATURE_1_ON is disabled. 
#pragma shader_feature FEATURE_1_ON
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If you use shader_feature to create a set of two or more keywords, or you use multi_compile, add _ when you declare a keyword set so that Unity creates an additional variant or uniform integer. For example:

// Creates 5 shader variants, including one for when RED, GREEN, BLUE, and WHITE are all disabled. 
#pragma shader_feature _ RED GREEN BLUE WHITE

// Creates 2 shader variants, including one for when FEATURE_3_ON is disabled.
#pragma multi_compile _ FEATURE_3_ON
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Use other statements to make shader behavior conditional

You can also use the following HLSL pre-processor directives to create conditional code:

• #if, #elif, #else and #endif.
• #ifdef and #ifndef.