Engine Setup

The plugin uses a GBuffer to encode data. The default setup is easiest to setup, and recommended for most projects.

Default Setup - Material AO channel

The default setup uses the material Ambient Occlusion channel to send data between the meshes in the scene and the shader through the GBuffer. We need a GBuffer texture to store our data, and with the launcher version of unreal we have to reuse an existing one.

Shader changes (Reference list)

Shader Patcher tool

The shader changes are listed here as reference. Use the shader patcher tool in the Setup to update these.

Prevent Specular/Metalic values from modifying the GBufferAO data

File: <UE5_installation>\Engine\Shaders\Private\BasePassPixelShader.usf
Expected text: GBuffer.GBufferAO = AOMultiBounce( Luminance( GBuffer.SpecularColor ), ShadingOcclusion.SpecOcclusion ).g;
Replace with:  // GBuffer.GBufferAO = AOMultiBounce( Luminance( GBuffer.SpecularColor ), ShadingOcclusion.SpecOcclusion ).g;

File: <UE5_installation>\Engine\Shaders\Private\MobileBasePassPixelShader.usf
Expected text: GBuffer.GBufferAO = AOMultiBounce(Luminance(GBuffer.SpecularColor), ShadingOcclusion.SpecOcclusion).g;
Replace with:  // GBuffer.GBufferAO = AOMultiBounce(Luminance(GBuffer.SpecularColor), ShadingOcclusion.SpecOcclusion).g;

Prevent SubSurfaceScattering shading model from using GBufferAO

File: <UE5_installation>\Engine\Shaders\Private\ShadingModels.ush
Expected text: const half BackScatter = GBuffer.GBufferAO * NormalContribution / (PI * 2);
Replace with:  const half BackScatter = NormalContribution / (PI * 2);

Prevent non lumen lighting from using GBufferAO

File: <UE5_installation>\Engine\Shaders\Private\ReflectionEnvironmentPixelShader.usf
Expected text: float AO = GBuffer.GBufferAO * AmbientOcclusion;
Replace with:  float AO = AmbientOcclusion;

File: <UE5_installation>\Engine\Shaders\Private\SkyLightingDiffuseShared.ush
Expected text: FSkyLightVisibilityData SkyVisData = GetSkyLightVisibilityData(SkyLightingNormal, GBuffer.WorldNormal, GBuffer.GBufferAO, AmbientOcclusion, BentNormal);
Replace with:  FSkyLightVisibilityData SkyVisData = GetSkyLightVisibilityData(SkyLightingNormal, GBuffer.WorldNormal, 1, AmbientOcclusion, BentNormal);

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Custom Setup

The plugin needs a single channel GBuffer texture to store data. The plugin doesn't care which one, and it has been made to be easily changed.

1. Enable/Modify the GBuffer channel you want to use*

2. Hook the MeshBlend material function up to the desired output instead of the Ambient Occlusion in your materials

3. Update GetMeshBlendStencil(float2 UV) in MeshBlend\Shaders\MeshBlendTextures.usf to use the desired GBuffer channel

CAUTION*

This is an advanced way of setting it up, and will most likely require years of experience.
While this is supported by the plugin, setting it up is left to the user.