ShowFlag.LumenShortRangeAmbientOcclusion

ShowFlag.LumenShortRangeAmbientOcclusion

#Overview

name: ShowFlag.LumenShortRangeAmbientOcclusion

This variable is created as a Console Variable (cvar).

• type: Var
• help: Allows to override a specific showflag (works in editor and game, \

It is referenced in 4 C++ source files.

#Summary

#Usage in the C++ source code

The purpose of ShowFlag.LumenShortRangeAmbientOcclusion is to control the computation and display of short-range ambient occlusion in the Lumen global illumination system within Unreal Engine 5.

• This setting variable is primarily used by the Lumen subsystem, which is part of Unreal Engine 5’s rendering system.

• The value of this variable is likely set through the engine’s show flags system, which allows for runtime toggling of various rendering features.

• It interacts with other Lumen-related variables and settings, particularly those related to ambient occlusion and global illumination.

• Developers must be aware that this variable affects the visual quality and performance of the Lumen global illumination system. Enabling it will provide more accurate short-range shadows and occlusion but may have a performance cost.

• Best practices when using this variable include:

  1. Only enabling it when higher visual fidelity is required, as it may impact performance.
  2. Testing the impact on different hardware configurations to ensure acceptable performance.
  3. Using it in conjunction with other Lumen settings for optimal results.

Regarding the associated variable LumenShortRangeAmbientOcclusion:

• This variable serves the same purpose as ShowFlag.LumenShortRangeAmbientOcclusion, controlling the short-range ambient occlusion feature in Lumen.

• It is used in the Renderer module, specifically in the Lumen-related components such as LumenReSTIRGather and LumenScreenProbeGather.

• The value is checked in conditional statements to determine whether to compute and apply short-range ambient occlusion.

• It interacts with other Lumen settings like GLumenReSTIRGatherShortRangeAmbientOcclusion and GLumenShortRangeAmbientOcclusion.

• Developers should be aware that this variable directly affects the rendering pipeline and can influence both visual quality and performance.

• Best practices include:

  1. Coordinating its use with other Lumen settings for consistent results.
  2. Profiling the performance impact when enabled, especially in complex scenes.
  3. Considering its interaction with other ambient occlusion techniques in the engine.

#References in C++ code

#Callsites

This variable is referenced in the following C++ source code:

#Loc: <Workspace>/Engine/Source/Runtime/Engine/Public/ShowFlagsValues.inl:441

Scope: file

Source code excerpt:

SHOWFLAG_ALWAYS_ACCESSIBLE(LumenSecondaryBounces, SFG_Lumen, NSLOCTEXT("UnrealEd", "LumenSecondaryBouncesSF", "Secondary Bounces"))
/** Compute screen space directional occlusion in Lumen */
SHOWFLAG_ALWAYS_ACCESSIBLE(LumenShortRangeAmbientOcclusion, SFG_Lumen, NSLOCTEXT("UnrealEd", "LumenShortRangeAmbientOcclusionSF", "Short Range Ambient Occlusion"))

/** Draw Nanite meshes */
SHOWFLAG_ALWAYS_ACCESSIBLE(NaniteMeshes, SFG_Nanite, NSLOCTEXT("UnrealEd", "NaniteMeshesSF", "Meshes"))
/** Draw Nanite streaming geometry */
SHOWFLAG_ALWAYS_ACCESSIBLE(NaniteStreamingGeometry, SFG_Nanite, NSLOCTEXT("UnrealEd", "NaniteStreamingGeometrySF", "Streaming Geometry"))

#Associated Variable and Callsites

This variable is associated with another variable named LumenShortRangeAmbientOcclusion. They share the same value. See the following C++ source code.

#Loc: <Workspace>/Engine/Source/Runtime/Engine/Public/ShowFlagsValues.inl:441

Scope: file

Source code excerpt:

SHOWFLAG_ALWAYS_ACCESSIBLE(LumenSecondaryBounces, SFG_Lumen, NSLOCTEXT("UnrealEd", "LumenSecondaryBouncesSF", "Secondary Bounces"))
/** Compute screen space directional occlusion in Lumen */
SHOWFLAG_ALWAYS_ACCESSIBLE(LumenShortRangeAmbientOcclusion, SFG_Lumen, NSLOCTEXT("UnrealEd", "LumenShortRangeAmbientOcclusionSF", "Short Range Ambient Occlusion"))

/** Draw Nanite meshes */
SHOWFLAG_ALWAYS_ACCESSIBLE(NaniteMeshes, SFG_Nanite, NSLOCTEXT("UnrealEd", "NaniteMeshesSF", "Meshes"))
/** Draw Nanite streaming geometry */
SHOWFLAG_ALWAYS_ACCESSIBLE(NaniteStreamingGeometry, SFG_Nanite, NSLOCTEXT("UnrealEd", "NaniteStreamingGeometrySF", "Streaming Geometry"))

#Loc: <Workspace>/Engine/Source/Runtime/Renderer/Private/Lumen/LumenReSTIRGather.cpp:1294

Scope (from outer to inner):

file
function     FSSDSignalTextures FDeferredShadingSceneRenderer::RenderLumenReSTIRGather

Source code excerpt:

	DenoiserOutputs.Textures[2] = RoughSpecularIndirect;

	if (GLumenReSTIRGatherShortRangeAmbientOcclusion != 0 && ViewFamily.EngineShowFlags.LumenShortRangeAmbientOcclusion)
	{
		float MaxScreenTraceFraction = GLumenReSTIRGatherShortRangeAOMaxScreenTraceFraction;
		ScreenSpaceBentNormalParameters = ComputeScreenSpaceShortRangeAO(GraphBuilder, Scene, View, SceneTextures, LightingChannelsTexture, BlueNoise, MaxScreenTraceFraction, 1.0f, ComputePassFlags);
	}

	return DenoiserOutputs;

#Loc: <Workspace>/Engine/Source/Runtime/Renderer/Private/Lumen/LumenScreenProbeGather.cpp:369

Scope (from outer to inner):

file
namespace    LumenScreenProbeGather
function     bool UseShortRangeAmbientOcclusion

Source code excerpt:

	bool UseShortRangeAmbientOcclusion(const FEngineShowFlags& ShowFlags)
	{
		return GLumenScreenProbeGatherReferenceMode ? false : (GLumenShortRangeAmbientOcclusion != 0 && ShowFlags.LumenShortRangeAmbientOcclusion);
	}

	bool ApplyShortRangeAODuringIntegration()
	{
		return GLumenShortRangeAOApplyDuringIntegration != 0;
	}