p.gc.BuildGeometryForChildrenOnPT
p.gc.BuildGeometryForChildrenOnPT
#Overview
name: p.gc.BuildGeometryForChildrenOnPT
This variable is created as a Console Variable (cvar).
- type:
Var - help:
If true build all children geometry on Physics Thread at initilaization time, otherwise wait until destruction occurs.
It is referenced in 7 C++ source files.
#Summary
#Usage in the C++ source code
The purpose of p.gc.BuildGeometryForChildrenOnPT is to control the timing of geometry building for children in the Chaos physics system of Unreal Engine 5. Specifically, it determines whether to build all children geometry on the Physics Thread at initialization time or wait until destruction occurs.
This setting variable is primarily used in the Chaos physics system, which is part of Unreal Engine’s experimental physics framework. It is referenced in the GeometryCollectionPhysicsProxy and PBDRigidClustering modules.
The value of this variable is set using an FAutoConsoleVariableRef, which allows it to be modified at runtime through console commands. It is initialized to true by default.
The associated variable bBuildGeometryForChildrenOnPT interacts directly with this setting. They share the same value and are used interchangeably in the code.
Developers must be aware that this variable affects the performance and behavior of the physics simulation, particularly for Geometry Collections. When set to true, it may increase initialization time but potentially improve runtime performance by having all geometry ready. When false, it may lead to faster initialization but could cause delays when destruction occurs.
Best practices when using this variable include:
- Consider the trade-off between initialization time and runtime performance for your specific use case.
- Test both true and false settings to determine which works best for your project.
- Be consistent in its usage across related systems to avoid unexpected behavior.
Regarding the associated variable bBuildGeometryForChildrenOnPT:
- It serves the same purpose as p.gc.BuildGeometryForChildrenOnPT.
- It is used directly in the Chaos physics system code, particularly in the GeometryCollectionPhysicsProxy and PBDRigidClustering modules.
- Its value is set by the console variable p.gc.BuildGeometryForChildrenOnPT.
- It interacts with other variables like bBuildGeometryForChildrenOnGT and bCreateGTParticleForChildren, which control similar behaviors on the Game Thread.
- Developers should treat it as they would p.gc.BuildGeometryForChildrenOnPT, as they are effectively the same variable.
- Best practices include using it consistently within physics-related code and considering its impact on performance and behavior when making changes.
#References in C++ code
#Callsites
This variable is referenced in the following C++ source code:
#Loc: <Workspace>/Engine/Source/Runtime/Experimental/Chaos/Private/PhysicsProxy/GeometryCollectionPhysicsProxy.cpp:544
Scope: file
Source code excerpt:
CHAOS_API bool bBuildGeometryForChildrenOnPT = true;
FAutoConsoleVariableRef CVarbBuildGeometryForChildrenOnPT(TEXT("p.gc.BuildGeometryForChildrenOnPT"), bBuildGeometryForChildrenOnPT, TEXT("If true build all children geometry on Physics Thread at initilaization time, otherwise wait until destruction occurs."));
bool bBuildGeometryForChildrenOnGT = true;
FAutoConsoleVariableRef CVarbBuildGeometryForChildrenOnGT(TEXT("p.gc.BuildGeometryForChildrenOnGT"), bBuildGeometryForChildrenOnGT, TEXT("If true build all children geometry on Game Thread at initilaization time, otherwise wait until destruction occurs."));
bool bCreateGTParticleForChildren = true;
FAutoConsoleVariableRef CVarCreateGTParticleForChildren(TEXT("p.gc.CreateGTParticlesForChildren"), bCreateGTParticleForChildren, TEXT("If true create all children particles at initilaization time, otherwise wait until destruction occurs."));
#Associated Variable and Callsites
This variable is associated with another variable named bBuildGeometryForChildrenOnPT. They share the same value. See the following C++ source code.
#Loc: <Workspace>/Engine/Source/Runtime/Experimental/Chaos/Private/Chaos/PBDRigidClustering.cpp:26
Scope: file
Source code excerpt:
#include "CoreMinimal.h"
extern CHAOS_API bool bBuildGeometryForChildrenOnPT;
namespace Chaos
{
//
// Connectivity PVar
//
#Loc: <Workspace>/Engine/Source/Runtime/Experimental/Chaos/Private/Chaos/PBDRigidClustering.cpp:1148
Scope (from outer to inner):
file
namespace Chaos
function TSet<FPBDRigidParticleHandle*> FRigidClustering::ReleaseClusterParticlesImpl
Source code excerpt:
ShockDamagePropagationFactor = SimParams.ShockDamagePropagationFactor;
if (bBuildGeometryForChildrenOnPT == false)
{
GenerateEdges(*ConcreteGCProxy, *ClusteredParticle, ClusterUnionManager);
}
}
TArray<FPBDRigidParticleHandle*>& Children = MChildren[ClusteredParticle];
#Loc: <Workspace>/Engine/Source/Runtime/Experimental/Chaos/Private/PhysicsProxy/GeometryCollectionPhysicsProxy.cpp:543
Scope: file
Source code excerpt:
FAutoConsoleVariableRef CVarReportHighParticleFraction(TEXT("p.gc.ReportHighParticleFraction"), ReportHighParticleFraction, TEXT("Report any objects with particle fraction above this threshold"));
CHAOS_API bool bBuildGeometryForChildrenOnPT = true;
FAutoConsoleVariableRef CVarbBuildGeometryForChildrenOnPT(TEXT("p.gc.BuildGeometryForChildrenOnPT"), bBuildGeometryForChildrenOnPT, TEXT("If true build all children geometry on Physics Thread at initilaization time, otherwise wait until destruction occurs."));
bool bBuildGeometryForChildrenOnGT = true;
FAutoConsoleVariableRef CVarbBuildGeometryForChildrenOnGT(TEXT("p.gc.BuildGeometryForChildrenOnGT"), bBuildGeometryForChildrenOnGT, TEXT("If true build all children geometry on Game Thread at initilaization time, otherwise wait until destruction occurs."));
bool bCreateGTParticleForChildren = true;
FAutoConsoleVariableRef CVarCreateGTParticleForChildren(TEXT("p.gc.CreateGTParticlesForChildren"), bCreateGTParticleForChildren, TEXT("If true create all children particles at initilaization time, otherwise wait until destruction occurs."));
#Loc: <Workspace>/Engine/Source/Runtime/Experimental/Chaos/Private/PhysicsProxy/GeometryCollectionPhysicsProxy.cpp:1220
Scope (from outer to inner):
file
function void FGeometryCollectionPhysicsProxy::InitializeBodiesPT
Source code excerpt:
bIsInitializedOnPhysicsThread = true;
// Building geometry according to the cVar
bHasBuiltGeometryOnPT = bBuildGeometryForChildrenOnPT;
if (Parameters.Simulating && RestCollection)
{
const TManagedArray<int32>& BoneMap = RestCollection->BoneMap;
const TManagedArray<int32>& SimulationType = RestCollection->SimulationType;
const TManagedArray<FVector3f>& Vertex = RestCollection->Vertex;
#Loc: <Workspace>/Engine/Source/Runtime/Experimental/Chaos/Private/PhysicsProxy/GeometryCollectionPhysicsProxy.cpp:1289
Scope (from outer to inner):
file
function void FGeometryCollectionPhysicsProxy::InitializeBodiesPT
lambda-function
Source code excerpt:
Parameters.Shared,
Simplicials[TransformGroupIndex].Get(),
(bBuildGeometryForChildrenOnPT || (TransformGroupIndex == Parameters.InitialRootIndex)) ? Implicits[TransformGroupIndex] : nullptr,
SimFilter,
QueryFilter,
ScaledMass,
ScaledInertia,
Transforms[TransformGroupIndex],
DynamicState[TransformGroupIndex],
#Loc: <Workspace>/Engine/Source/Runtime/Experimental/Chaos/Private/PhysicsProxy/GeometryCollectionPhysicsProxy.cpp:1959
Scope (from outer to inner):
file
function Chaos::TPBDGeometryCollectionParticleHandle<Chaos::FReal, 3>* FGeometryCollectionPhysicsProxy::BuildNonClusters_Internal
Source code excerpt:
Parameters.Shared,
Simplicials[CollectionClusterIndex].Get(),
(bBuildGeometryForChildrenOnPT || (CollectionClusterIndex == Parameters.InitialRootIndex)) ? Implicits[CollectionClusterIndex] : nullptr,
SimFilter,
QueryFilter,
Mass,
Inertia,
ParticleTM,
static_cast<uint8>(DynamicState[CollectionClusterIndex]),