What It Means & How to Fix It in UE5

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🧠 Why You’re Seeing This Error

This error means Unreal Engine tried to compile or register a shader type that depends on a Vertex Factory, but:

• You didn’t associate the shader with a Vertex Factory
• You’re using a shader base class (like FMeshMaterialShader) that requires mesh data, but you’re registering it like a global shader
• You’re missing key Vertex Factory includes (e.g., VertexFactory.ush)
• Your shader stage is improperly configured for how UE5 expects vertex input handling

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Vertex Factories are Unreal’s system for feeding vertex data (position, UVs, normals, etc.) into GPU shaders — especially used in mesh materials, custom materials, and procedural geometry pipelines.

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💥 Example Error Message

Fatal Error: Shader type requires a vertex factory but none was specified

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🛠️ Common Shader Scenarios That Cause This

❌ Shader Class Inherits From FMeshMaterialShader or FMaterialShader Without a Factory

class FMyShader : public FMaterialShader // ❌ requires a vertex factory binding

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❌ Shader Doesn’t Include or Use VertexFactory.ush

#include "/Engine/Private/VertexFactory.ush" // ✅ Required for vertex factory-based shaders

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❌ Registered as a Global Shader When It Should Be a Material Shader

IMPLEMENT_SHADER_TYPE(, FMyShader, TEXT("/Shaders/MyShader.usf"), TEXT("MainVS"), SF_Vertex);
// ❌ Shader expects a mesh/material pipeline, not a global shader

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✅ How to Fix It in UE5 – Step-by-Step

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✔️ 1. Use the Correct Shader Base Class

If your shader needs mesh/vertex data:

• Use FMeshMaterialShader or FMaterialShader
• Provide a vertex factory type when registering

Example:

IMPLEMENT_MATERIAL_SHADER_TYPE(
    , FMyMeshShader,
    TEXT("/Shaders/MyShader.usf"),
    TEXT("MainVS"),
    SF_Vertex
)

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✔️ 2. Provide a Vertex Factory in Shader Registration

Vertex factories like:

FLocalVertexFactory
FNiagaraVertexFactory
FLandscapeVertexFactory

You must bind your shader to a factory if it uses FMaterialShader or FMeshMaterialShader.

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✔️ 3. Include the Vertex Factory Shader Header

Inside your .usf shader file:

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

This gives access to macros like:

GetVertexFactoryInterpolants()
TransformLocalToWorld()

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✔️ 4. Don’t Use Global Shader Classes for Material Mesh Shaders

Avoid:

class FMyMaterialShader : public FGlobalShader // ❌ not valid for mesh-based logic

Use:

class FMyMaterialShader : public FMaterialShader // ✅

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✔️ 5. Provide Required Metadata in ShouldCompilePermutation

Make sure you’re returning true for valid vertex factories:

static bool ShouldCompilePermutation(const FMaterialShaderPermutationParameters& Parameters)
{
    return Parameters.VertexFactoryType->GetName() == FLocalVertexFactory::StaticType->GetName();
}

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✅ Summary: How to Fix “Shader Type Requires a Vertex Factory But None Was Specified” in UE5

Cause	Fix Example
Shader uses FMaterialShader or FMeshMaterialShader	Provide a valid vertex factory binding
No vertex factory declared	Add #include "/Engine/Private/VertexFactory.ush"
Wrong shader class used	Use FMaterialShader for mesh-based shading
Global shader misused for mesh data	Register as a material shader with proper permutation logic