p.Chaos.ImmPhys.PositionIterations
p.Chaos.ImmPhys.PositionIterations
#Overview
name: p.Chaos.ImmPhys.PositionIterations
This variable is created as a Console Variable (cvar).
- type:
Var - help:
Override number of position iteration loops in immediate physics (if >= 0)
It is referenced in 3 C++ source files.
#Summary
#Usage in the C++ source code
The purpose of p.Chaos.ImmPhys.PositionIterations is to control the number of position iteration loops in the immediate physics simulation of Unreal Engine’s Chaos physics system. This setting is specifically used for fine-tuning the accuracy and performance of physics simulations.
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This setting variable is primarily used by the Chaos physics system, which is part of Unreal Engine’s physics engine. It’s specifically utilized in the Immediate Physics module of Chaos.
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The value of this variable is set through the Unreal Engine console variable system. It’s defined as an FAutoConsoleVariableRef, which allows it to be modified at runtime through console commands or configuration files.
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The associated variable ChaosImmediate_Evolution_PositionIterations directly interacts with p.Chaos.ImmPhys.PositionIterations. They share the same value and are used interchangeably in the code.
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Developers must be aware that this variable only takes effect if its value is greater than or equal to 0. A negative value means the default number of position iterations will be used.
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Best practices when using this variable include:
- Only modify it if you understand the implications on physics simulation accuracy and performance.
- Use it in conjunction with VelocityIterations and ProjectionIterations for balanced physics simulation.
- Monitor performance impacts when increasing the number of iterations.
Regarding the associated variable ChaosImmediate_Evolution_PositionIterations:
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Its purpose is identical to p.Chaos.ImmPhys.PositionIterations, serving as the internal representation of the console variable.
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It’s used directly in the physics simulation code, specifically in the FSimulation::Simulate function of the ImmediatePhysics_Chaos namespace.
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The value is set initially to -1, which means it will use the default number of position iterations unless overridden by the console variable.
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This variable is used alongside other iteration variables (VelocityIterations and ProjectionIterations) to control the physics solver’s behavior.
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Developers should be aware that modifying this variable directly in code might be overridden by the console variable at runtime.
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Best practice is to use the console variable (p.Chaos.ImmPhys.PositionIterations) for runtime adjustments and leave the direct variable manipulation to the engine’s internal systems.
#References in C++ code
#Callsites
This variable is referenced in the following C++ source code:
#Loc: <Workspace>/Engine/Source/Runtime/Engine/Private/PhysicsEngine/ImmediatePhysics/ImmediatePhysicsChaos/ImmediatePhysicsSimulation_Chaos.cpp:47
Scope: file
Source code excerpt:
FAutoConsoleVariableRef CVarChaosImmPhysInitialStepTime(TEXT("p.Chaos.ImmPhys.InitialStepTime"), ChaosImmediate_Evolution_InitialStepTime, TEXT("Initial step time (then calculated from rolling average)"));
FAutoConsoleVariableRef CVarChaosImmPhysDeltaTimeCount(TEXT("p.Chaos.ImmPhys.DeltaTimeCount"), ChaosImmediate_Evolution_DeltaTimeCount, TEXT("The number of ticks over which the moving average is calculated"));
FAutoConsoleVariableRef CVarChaosImmPhysPositionIterations(TEXT("p.Chaos.ImmPhys.PositionIterations"), ChaosImmediate_Evolution_PositionIterations, TEXT("Override number of position iteration loops in immediate physics (if >= 0)"));
FAutoConsoleVariableRef CVarChaosImmPhysVelocityIterations(TEXT("p.Chaos.ImmPhys.VelocityIterations"), ChaosImmediate_Evolution_VelocityIterations, TEXT("Override number of velocity iteration loops in immediate physics (if >= 0)"));
FAutoConsoleVariableRef CVarChaosImmPhysProjectionIterations(TEXT("p.Chaos.ImmPhys.ProjectionIterations"), ChaosImmediate_Evolution_ProjectionIterations, TEXT("Override number of projection iteration loops in immediate physics (if >= 0)"));
FAutoConsoleVariableRef CVarChaosImmPhysDisableInactiveByIndex(TEXT("p.Chaos.ImmPhys.DisableInactiveByIndex"), ChaosImmediate_DisableInactiveByIndex, TEXT("Disable bodies that are no longer active based on the index, rather than just count."));
FAutoConsoleVariableRef CVarChaosImmPhysNumCollisionsPerBlock(TEXT("p.Chaos.ImmPhys.NumCollisionsPerBlock"), ChaosImmediate_Evolution_NumCollisionsPerBlock, TEXT("The number of collision in a block in the collision pool. Higher values give better cache efficieny but waste memory if you do not need that many"));
Chaos::FRealSingle ChaosImmediate_Evolution_SimSpaceCentrifugalAlpha = 1.0f;
#Associated Variable and Callsites
This variable is associated with another variable named ChaosImmediate_Evolution_PositionIterations. They share the same value. See the following C++ source code.
#Loc: <Workspace>/Engine/Source/Runtime/Engine/Private/PhysicsEngine/ImmediatePhysics/ImmediatePhysicsChaos/ImmediatePhysicsSimulation_Chaos.cpp:38
Scope: file
Source code excerpt:
Chaos::FRealSingle ChaosImmediate_Evolution_InitialStepTime = 0.033f;
int32 ChaosImmediate_Evolution_DeltaTimeCount = 100;
int32 ChaosImmediate_Evolution_PositionIterations = -1;
int32 ChaosImmediate_Evolution_VelocityIterations = -1;
int32 ChaosImmediate_Evolution_ProjectionIterations = -1;
int32 ChaosImmediate_DisableInactiveByIndex = 1;
int32 ChaosImmediate_Evolution_NumCollisionsPerBlock = 50;
FAutoConsoleVariableRef CVarChaosImmPhysStepTime(TEXT("p.Chaos.ImmPhys.StepTime"), ChaosImmediate_Evolution_StepTime, TEXT("Override step time (if not zero)"));
FAutoConsoleVariableRef CVarChaosImmPhysNumSteps(TEXT("p.Chaos.ImmPhys.NumSteps"), ChaosImmediate_Evolution_NumSteps, TEXT("Override num steps (if not zero)"));
FAutoConsoleVariableRef CVarChaosImmPhysInitialStepTime(TEXT("p.Chaos.ImmPhys.InitialStepTime"), ChaosImmediate_Evolution_InitialStepTime, TEXT("Initial step time (then calculated from rolling average)"));
FAutoConsoleVariableRef CVarChaosImmPhysDeltaTimeCount(TEXT("p.Chaos.ImmPhys.DeltaTimeCount"), ChaosImmediate_Evolution_DeltaTimeCount, TEXT("The number of ticks over which the moving average is calculated"));
FAutoConsoleVariableRef CVarChaosImmPhysPositionIterations(TEXT("p.Chaos.ImmPhys.PositionIterations"), ChaosImmediate_Evolution_PositionIterations, TEXT("Override number of position iteration loops in immediate physics (if >= 0)"));
FAutoConsoleVariableRef CVarChaosImmPhysVelocityIterations(TEXT("p.Chaos.ImmPhys.VelocityIterations"), ChaosImmediate_Evolution_VelocityIterations, TEXT("Override number of velocity iteration loops in immediate physics (if >= 0)"));
FAutoConsoleVariableRef CVarChaosImmPhysProjectionIterations(TEXT("p.Chaos.ImmPhys.ProjectionIterations"), ChaosImmediate_Evolution_ProjectionIterations, TEXT("Override number of projection iteration loops in immediate physics (if >= 0)"));
FAutoConsoleVariableRef CVarChaosImmPhysDisableInactiveByIndex(TEXT("p.Chaos.ImmPhys.DisableInactiveByIndex"), ChaosImmediate_DisableInactiveByIndex, TEXT("Disable bodies that are no longer active based on the index, rather than just count."));
FAutoConsoleVariableRef CVarChaosImmPhysNumCollisionsPerBlock(TEXT("p.Chaos.ImmPhys.NumCollisionsPerBlock"), ChaosImmediate_Evolution_NumCollisionsPerBlock, TEXT("The number of collision in a block in the collision pool. Higher values give better cache efficieny but waste memory if you do not need that many"));
Chaos::FRealSingle ChaosImmediate_Evolution_SimSpaceCentrifugalAlpha = 1.0f;
#Loc: <Workspace>/Engine/Source/Runtime/Engine/Private/PhysicsEngine/ImmediatePhysics/ImmediatePhysicsChaos/ImmediatePhysicsSimulation_Chaos.cpp:865
Scope (from outer to inner):
file
namespace ImmediatePhysics_Chaos
function void FSimulation::Simulate
Source code excerpt:
ChaosImmediate_Collision_MaxDepenetrationVelocity,
ChaosImmediate_Joint_UseLinearSolver,
ChaosImmediate_Evolution_PositionIterations,
ChaosImmediate_Evolution_VelocityIterations,
ChaosImmediate_Evolution_ProjectionIterations);
FPBDJointSolverSettings JointsSettings = Implementation->Joints.GetSettings();
JointsSettings.SwingTwistAngleTolerance = ChaosImmediate_Joint_SwingTwistAngleTolerance;
JointsSettings.PositionTolerance = ChaosImmediate_Joint_PositionTolerance;