r.SkyLight.RealTimeReflectionCapture.TimeSlice
r.SkyLight.RealTimeReflectionCapture.TimeSlice
#Overview
name: r.SkyLight.RealTimeReflectionCapture.TimeSlice
This variable is created as a Console Variable (cvar).
- type:
Var - help:
When enabled, the real-time sky light capture and convolutions will by distributed over several frames to lower the per-frame cost.
It is referenced in 7 C++ source files.
#Summary
#Usage in the C++ source code
The purpose of r.SkyLight.RealTimeReflectionCapture.TimeSlice is to control the time-slicing of real-time sky light capture and convolutions in Unreal Engine’s rendering system. This setting allows the engine to distribute the computation of sky light reflections over several frames, reducing the per-frame performance cost.
The Unreal Engine subsystem that primarily relies on this setting variable is the Renderer module, specifically the real-time reflection capture system for sky lights.
The value of this variable is set through a console variable (CVar) system. It can be modified at runtime or set in configuration files.
The associated variable CVarRealTimeReflectionCaptureTimeSlicing interacts directly with r.SkyLight.RealTimeReflectionCapture.TimeSlice. They share the same value and purpose.
Developers must be aware of the following when using this variable:
- Enabling time-slicing (value > 0) can improve performance by distributing the reflection capture workload across multiple frames.
- Disabling time-slicing (value = 0) ensures that the sky light reflection is fully captured each frame, which may be necessary for consistency in certain scenarios (e.g., movie rendering).
- The variable is render thread safe, meaning it can be changed safely at runtime without causing threading issues.
Best practices when using this variable include:
- Enable time-slicing (set to 1) for general gameplay to improve performance.
- Disable time-slicing (set to 0) when capturing high-quality screenshots or rendering movies to ensure consistent lighting across frames.
- Consider the trade-off between performance and lighting update frequency when adjusting this setting.
Regarding the associated variable CVarRealTimeReflectionCaptureTimeSlicing:
- It serves the same purpose as r.SkyLight.RealTimeReflectionCapture.TimeSlice.
- It is used internally in the rendering code to check if time-slicing should be applied.
- The variable is defined using TAutoConsoleVariable, allowing it to be easily modified through the console or configuration files.
- Developers should treat this variable identically to r.SkyLight.RealTimeReflectionCapture.TimeSlice when considering its impact on the rendering system.
#References in C++ code
#Callsites
This variable is referenced in the following C++ source code:
#Loc: <Workspace>/Engine/Source/Runtime/Renderer/Private/ReflectionEnvironmentRealTimeCapture.cpp:31
Scope: file
Source code excerpt:
static TAutoConsoleVariable<int32> CVarRealTimeReflectionCaptureTimeSlicing(
TEXT("r.SkyLight.RealTimeReflectionCapture.TimeSlice"), 1,
TEXT("When enabled, the real-time sky light capture and convolutions will by distributed over several frames to lower the per-frame cost."),
ECVF_RenderThreadSafe);
static TAutoConsoleVariable<int32> CVarRealTimeReflectionCaptureTimeSlicingSkyCloudCubeFacePerFrame(
TEXT("r.SkyLight.RealTimeReflectionCapture.TimeSlice.SkyCloudCubeFacePerFrame"), 6,
TEXT("When enabled, the real-time sky light capture, when time sliced, will not render cloud in all cube face in a single frame; but one face per frame. That is to distribute the cloud tracing cost even more, but will add latency and potentially can result in lighting discrepancy between faces if the sun is moving fast. Value in [1,6]."),
#Loc: <Workspace>/Engine/Plugins/MovieScene/MovieRenderPipeline/Source/MovieRenderPipelineCore/Private/Graph/Nodes/MovieGraphGlobalGameOverrides.cpp:78
Scope (from outer to inner):
file
function void UMovieGraphGlobalGameOverridesNode::BuildNewProcessCommandLineArgsImpl
Source code excerpt:
InOutDeviceProfileCvars.Add(FString::Printf(TEXT("a.URO.Enable=%d"), 0));
InOutDeviceProfileCvars.Add(FString::Printf(TEXT("r.SkyLight.RealTimeReflectionCapture.TimeSlice=%d"), 0));
InOutDeviceProfileCvars.Add(FString::Printf(TEXT("r.VolumetricRenderTarget=%d"), 1));
InOutDeviceProfileCvars.Add(FString::Printf(TEXT("r.VolumetricRenderTarget.Mode=%d"), 3));
InOutDeviceProfileCvars.Add(FString::Printf(TEXT("wp.Runtime.BlockOnSlowStreaming=%d"), 0));
InOutDeviceProfileCvars.Add(FString::Printf(TEXT("p.Chaos.ImmPhys.MinStepTime=%d"), 0));
InOutDeviceProfileCvars.Add(FString::Printf(TEXT("r.SkipRedundantTransformUpdate=%d"), 0));
InOutDeviceProfileCvars.Add(FString::Printf(TEXT("p.ChaosCloth.UseTimeStepSmoothing=%d"), 0));
#Loc: <Workspace>/Engine/Plugins/MovieScene/MovieRenderPipeline/Source/MovieRenderPipelineCore/Private/Graph/Nodes/MovieGraphGlobalGameOverrides.cpp:150
Scope (from outer to inner):
file
function void UMovieGraphGlobalGameOverridesNode::ApplySettings
Source code excerpt:
// To make sure that the skylight is always valid and consistent across capture sessions, we enforce a full capture each frame, accepting a small GPU cost.
MOVIEPIPELINE_STORE_AND_OVERRIDE_CVAR_INT(PreviousSkyLightRealTimeReflectionCaptureTimeSlice, TEXT("r.SkyLight.RealTimeReflectionCapture.TimeSlice"), 0, bOverrideValues);
// Cloud are rendered using high quality volumetric render target mode 3: per pixel tracing and composition on screen, while supporting cloud on translucent.
MOVIEPIPELINE_STORE_AND_OVERRIDE_CVAR_INT(PreviousVolumetricRenderTarget, TEXT("r.VolumetricRenderTarget"), 1, bOverrideValues);
MOVIEPIPELINE_STORE_AND_OVERRIDE_CVAR_INT(PreviousVolumetricRenderTargetMode, TEXT("r.VolumetricRenderTarget.Mode"), 3, bOverrideValues);
// To make sure that the world partition streaming doesn't end up in critical streaming performances and stops streaming low priority cells.
#Loc: <Workspace>/Engine/Plugins/MovieScene/MovieRenderPipeline/Source/MovieRenderPipelineCore/Private/MoviePipelineGameOverrideSetting.cpp:117
Scope (from outer to inner):
file
function void UMoviePipelineGameOverrideSetting::ApplyCVarSettings
Source code excerpt:
// To make sure that the skylight is always valid and consistent accross capture sessions, we enforce a full capture each frame, accepting a small GPU cost.
MOVIEPIPELINE_STORE_AND_OVERRIDE_CVAR_INT(PreviousSkyLightRealTimeReflectionCaptureTimeSlice, TEXT("r.SkyLight.RealTimeReflectionCapture.TimeSlice"), 0, bOverrideValues);
// Cloud are rendered using high quality volumetric render target mode 3: per pixel tracing and composition on screen, while supporting cloud on translucent.
MOVIEPIPELINE_STORE_AND_OVERRIDE_CVAR_INT(PreviousVolumetricRenderTarget, TEXT("r.VolumetricRenderTarget"), 1, bOverrideValues);
MOVIEPIPELINE_STORE_AND_OVERRIDE_CVAR_INT(PreviousVolumetricRenderTargetMode, TEXT("r.VolumetricRenderTarget.Mode"), 3, bOverrideValues);
// To make sure that the world partition streaming doesn't end up in critical streaming performances and stops streaming low priority cells.
#Loc: <Workspace>/Engine/Plugins/MovieScene/MovieRenderPipeline/Source/MovieRenderPipelineCore/Private/MoviePipelineGameOverrideSetting.cpp:237
Scope (from outer to inner):
file
function void UMoviePipelineGameOverrideSetting::BuildNewProcessCommandLineArgsImpl
Source code excerpt:
InOutDeviceProfileCvars.Add(FString::Printf(TEXT("au.NeverMuteNonRealtimeAudioDevices=%d"), 1));
InOutDeviceProfileCvars.Add(FString::Printf(TEXT("r.SkyLight.RealTimeReflectionCapture.TimeSlice=%d"), 0));
InOutDeviceProfileCvars.Add(FString::Printf(TEXT("r.VolumetricRenderTarget=%d"), 1));
InOutDeviceProfileCvars.Add(FString::Printf(TEXT("r.VolumetricRenderTarget.Mode=%d"), 3));
InOutDeviceProfileCvars.Add(FString::Printf(TEXT("wp.Runtime.BlockOnSlowStreaming=%d"), 0));
InOutDeviceProfileCvars.Add(FString::Printf(TEXT("p.Chaos.ImmPhys.MinStepTime=%d"), 0));
InOutDeviceProfileCvars.Add(FString::Printf(TEXT("r.SkipRedundantTransformUpdate=%d"), 0));
InOutDeviceProfileCvars.Add(FString::Printf(TEXT("p.ChaosCloth.UseTimeStepSmoothing=%d"), 0));
#Associated Variable and Callsites
This variable is associated with another variable named CVarRealTimeReflectionCaptureTimeSlicing. They share the same value. See the following C++ source code.
#Loc: <Workspace>/Engine/Source/Runtime/Renderer/Private/ReflectionEnvironmentRealTimeCapture.cpp:30
Scope: file
Source code excerpt:
static TAutoConsoleVariable<int32> CVarRealTimeReflectionCaptureTimeSlicing(
TEXT("r.SkyLight.RealTimeReflectionCapture.TimeSlice"), 1,
TEXT("When enabled, the real-time sky light capture and convolutions will by distributed over several frames to lower the per-frame cost."),
ECVF_RenderThreadSafe);
static TAutoConsoleVariable<int32> CVarRealTimeReflectionCaptureTimeSlicingSkyCloudCubeFacePerFrame(
TEXT("r.SkyLight.RealTimeReflectionCapture.TimeSlice.SkyCloudCubeFacePerFrame"), 6,
#Loc: <Workspace>/Engine/Source/Runtime/Renderer/Private/ReflectionEnvironmentRealTimeCapture.cpp:361
Scope: file
Source code excerpt:
FPooledRenderTargetDesc SkyCubeTexDesc = Translate(FSkyPassMeshProcessor::GetCaptureFrameSkyEnvMapTextureDesc(CubeWidth, CubeMipCount));
const bool bTimeSlicedRealTimeCapture = CVarRealTimeReflectionCaptureTimeSlicing.GetValueOnRenderThread() > 0 && !MainView.Family->bCurrentlyBeingEdited;
const bool CubeResolutionInvalidated = ConvolvedSkyRenderTargetReadyIndex < 0 || (ConvolvedSkyRenderTarget[ConvolvedSkyRenderTargetReadyIndex].IsValid() && ConvolvedSkyRenderTarget[ConvolvedSkyRenderTargetReadyIndex]->GetDesc().GetSize().X != CubeWidth);
if (!ConvolvedSkyRenderTarget[0].IsValid() || CubeResolutionInvalidated)
{
// Always allocated
GRenderTargetPool.FindFreeElement(GraphBuilder.RHICmdList, SkyCubeTexDesc, ConvolvedSkyRenderTarget[0], TEXT("SkyLight.ConvolvedSkyRenderTarget0"));