What It Means & How to Fix It in UE5

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🧠 Why You’re Seeing This Error

This error means your shader is using a macro, function, or type that’s defined in Common.usf, but you haven’t explicitly included that file in your shader source.

Unreal Engine 5 doesn’t automatically include Common.usf, so if you rely on things like:

• TransformWorldToClip()
• PI, TwoPi
• float3x3 CreateTangentToWorld()
• Math macros like saturate(), lerp(), etc. (in some cases)

…you must include the file manually or compilation will fail.

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💥 Example Error Message

error X3004: undeclared identifier 'TransformWorldToClip'
Missing #include of Common.usf

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🛠️ Common Shader Scenarios That Trigger This

❌ Using Functions Without Including the Header

float4 position = TransformWorldToClip(input.WorldPosition); // ❌ Fails without Common.usf

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❌ Using UE Math Constants Without Declaration

float angle = 2.0 * PI; // ❌ 'PI' not defined unless Common.usf is included

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✅ How to Fix “Missing #include of Common.usf” in UE5 – Step-by-Step

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✔️ 1. Add the Include at the Top of Your Shader File

Always include this near the top of your custom .usf file:

#include "/Engine/Private/Common.ush"

Or:

#include "/Engine/Private/Common.usf"

✅ Use .ush for smaller helper files
✅ Use .usf for full shader programs

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✔️ 2. Include Other Essential Shader Headers (Optional)

If you’re using Unreal’s rendering functions, you may also need:

#include "/Engine/Private/Definitions.usf"
#include "/Engine/Private/MaterialTemplate.ush"
#include "/Engine/Private/VertexFactory.ush"

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✔️ 3. Don’t Copy Code That Depends on Common.usf Without the Include

If you’re building a shader by copying pieces from Unreal’s internal shaders (e.g. BasePassPixelShader.usf), you must include all required headers, or macros and functions will be undefined.

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✔️ 4. Check Your IDE or Shader Include Paths (if using custom build)

Make sure your build setup allows Unreal to find engine-level shader files from:

Engine/Shaders/Private/

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✅ Summary: How to Fix “Missing #include of Common.usf” in UE5

Cause	Fix
Using engine functions/macros	Add #include "/Engine/Private/Common.ush" to your shader
Math constants or transforms undefined	Common.usf provides built-in definitions like PI, TransformWorldToClip()
Using internal shader fragments	Manually include required headers when copying from engine code