What It Means & How to Fix It in UE5

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🧠 Why You’re Seeing This Error

This error occurs when Unreal Engine attempts to compile a global shader (typically subclassed from FGlobalShader), but fails due to issues in the shader source code, registration, or required macros.

This is one of the most common errors when working with custom HLSL shaders in C++, especially when integrating .usf files.

You’re likely to see this when:

• You’ve created a new global shader class in C++
• The shader’s .usf file contains syntax errors or missing includes
• Your IMPLEMENT_SHADER_TYPE or ShouldCompilePermutation() macro is misconfigured
• A required permutation or feature macro is missing or incorrectly used

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💥 Example Error Message

LogShaderCompilers: Error: Failed to compile global shader FMyCustomShader

Accompanied by details like:

ShaderCompileWorker: error X3004: undeclared identifier 'TransformWorldToClip'
ShaderCompileWorker: error X3501: 'MainVS': entrypoint not found

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🛠️ Common Scenarios That Trigger This

❌ Your Shader File Is Missing an Entry Point Function

// FMyCustomShader expects "MainVS", but this doesn't exist in the shader file

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❌ You Forgot to Include Required Headers in the Shader

// Missing math macros, coordinate transforms, etc.
#include "/Engine/Private/Common.ush" // ✅ Required

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❌ The Shader Is Not Properly Registered in C++

IMPLEMENT_SHADER_TYPE(, FMyCustomShader, TEXT("/Shaders/MyCustomShader.usf"), TEXT("MainVS"), SF_Vertex);

• Path must be correct
• Entry point must match the .usf function
• Shader stage must be valid

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❌ Incorrect Permutation Conditions or Missing ShouldCompilePermutation

static bool ShouldCompilePermutation(...) {
    return Platform == SF_METAL; // ❌ Fails if compiling on Windows
}

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✅ How to Fix It in UE5 – Step-by-Step

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✔️ 1. Check That the Shader File Exists and Is Registered Properly

In C++:

IMPLEMENT_SHADER_TYPE(, FMyCustomShader, TEXT("/Shaders/MyCustomShader.usf"), TEXT("MainVS"), SF_Vertex);

Make sure:

• The file /Shaders/MyCustomShader.usf is located in your project or plugin shader folder
• The entry point MainVS exists in the shader file

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✔️ 2. Ensure You Have a Valid main()-like Function

In the .usf file:

void MainVS(
    in float4 InPosition : ATTRIBUTE0,
    out float4 OutPosition : SV_POSITION
) {
    OutPosition = InPosition;
}

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✔️ 3. Include All Required Shader Headers

At minimum:

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

Additional includes might be needed depending on what you use:

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

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✔️ 4. Check the Shader Stage

Match the shader function and the stage:

Stage	Macro value	Example Function
Vertex	SF_Vertex	MainVS
Pixel	SF_Pixel	MainPS
Compute	SF_Compute	MainCS

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✔️ 5. Clean and Rebuild Shader Cache

Sometimes errors persist due to stale data:

bashCopyEditDelete: DerivedDataCache/
Restart UE5 to recompile shaders

Or:

bashCopyEditShaderCompileWorker -clean

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✅ Summary: How to Fix “Failed to Compile Global Shader FMyCustomShader” in UE5

Cause	Fix
Entry point function missing	Define MainVS, MainPS, etc. in the .usf file
Shader not registered properly	Use IMPLEMENT_SHADER_TYPE with correct path and function name
Missing required includes	Add #include "/Engine/Private/Common.ush"
Bad permutation logic or platform mismatch	Correct ShouldCompilePermutation logic