p.Chaos.ImmPhys.Joint.SolvePositionLast
p.Chaos.ImmPhys.Joint.SolvePositionLast
#Overview
name: p.Chaos.ImmPhys.Joint.SolvePositionLast
This variable is created as a Console Variable (cvar).
- type:
Var - help:
Should we solve joints in position-then-rotation order (false) rotation-then-position order (true, default)
It is referenced in 4 C++ source files.
#Summary
#Usage in the C++ source code
The purpose of p.Chaos.ImmPhys.Joint.SolvePositionLast is to control the order of solving joint constraints in the Chaos physics engine’s immediate physics simulation. It determines whether joints should be solved in position-then-rotation order (false) or rotation-then-position order (true, default).
This setting variable is primarily used in the Chaos physics engine, which is part of Unreal Engine’s physics simulation system. Specifically, it’s used in the immediate physics simulation module, which is likely used for performance-critical or real-time physics calculations.
The value of this variable is set through the Unreal Engine console variable system. It’s defined using FAutoConsoleVariableRef, which allows it to be changed at runtime through console commands or configuration files.
The associated variable ChaosImmediate_Joint_SolvePositionLast directly interacts with p.Chaos.ImmPhys.Joint.SolvePositionLast. They share the same value, with ChaosImmediate_Joint_SolvePositionLast being the actual variable used in the code logic.
Developers should be aware that changing this variable will affect the behavior of joint simulations in the Chaos physics engine. Setting it to true (default) will solve rotation constraints before position constraints, while setting it to false will do the opposite.
Best practices when using this variable include:
- Testing thoroughly when changing the default value, as it may significantly impact physics simulation results.
- Consider performance implications, as the order of constraint solving can affect computation time.
- Use in conjunction with other joint-related settings for fine-tuning physics behavior.
Regarding the associated variable ChaosImmediate_Joint_SolvePositionLast:
- Its purpose is to store the actual value used in the physics simulation logic.
- It’s initialized with a default value of 1 (true).
- It’s used in the FSimulation::Simulate function to set the bSolvePositionLast property of JointsSettings.
- Developers should be aware that this variable is an int32, but it’s treated as a boolean in the code (non-zero values are considered true).
- Best practice is to modify this variable through the console variable system rather than directly in the code, to maintain consistency and allow for runtime adjustments.
#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:116
Scope: file
Source code excerpt:
FAutoConsoleVariableRef CVarChaosImmPhysJointAngleTolerance(TEXT("p.Chaos.ImmPhys.Joint.AngleTolerance"), ChaosImmediate_Joint_AngleTolerance, TEXT("AngleTolerance."));
FAutoConsoleVariableRef CVarChaosImmPhysJointNumShockPropagationIterations(TEXT("p.Chaos.ImmPhys.Joint.NumShockPropagationIterations"), ChaosImmediate_Joint_NumShockPropagationIterations, TEXT("How many iterations to run shock propagation for"));
FAutoConsoleVariableRef CVarChaosImmPhysJointSolvePositionLast(TEXT("p.Chaos.ImmPhys.Joint.SolvePositionLast"), ChaosImmediate_Joint_SolvePositionLast, TEXT("Should we solve joints in position-then-rotation order (false) rotation-then-position order (true, default)"));
FAutoConsoleVariableRef CVarChaosImmPhysJointUsePBDVelocityDrives(TEXT("p.Chaos.ImmPhys.Joint.UsePBDDrives"), ChaosImmediate_Joint_UsePositionBasedDrives, TEXT("Whether to solve drives in the position or velocity phase of the solver (default true)"));
FAutoConsoleVariableRef CVarChaosImmPhysJointEnableTwistLimits(TEXT("p.Chaos.ImmPhys.Joint.EnableTwistLimits"), ChaosImmediate_Joint_EnableTwistLimits, TEXT("EnableTwistLimits."));
FAutoConsoleVariableRef CVarChaosImmPhysJointEnableSwingLimits(TEXT("p.Chaos.ImmPhys.Joint.EnableSwingLimits"), ChaosImmediate_Joint_EnableSwingLimits, TEXT("EnableSwingLimits."));
FAutoConsoleVariableRef CVarChaosImmPhysJointEnableDrives(TEXT("p.Chaos.ImmPhys.Joint.EnableDrives"), ChaosImmediate_Joint_EnableDrives, TEXT("EnableDrives."));
FAutoConsoleVariableRef CVarChaosImmPhysJointLinearProjection(TEXT("p.Chaos.ImmPhys.Joint.LinearProjection"), ChaosImmediate_Joint_LinearProjection, TEXT("6Dof joint projection amount override (if >= 0)."));
FAutoConsoleVariableRef CVarChaosImmPhysJointAngularProjection(TEXT("p.Chaos.ImmPhys.Joint.AngularProjection"), ChaosImmediate_Joint_AngularProjection, TEXT("6Dof joint projection amount override (if >= 0)."));
#Associated Variable and Callsites
This variable is associated with another variable named ChaosImmediate_Joint_SolvePositionLast. They share the same value. See the following C++ source code.
#Loc: <Workspace>/Engine/Source/Runtime/Engine/Private/PhysicsEngine/ImmediatePhysics/ImmediatePhysicsChaos/ImmediatePhysicsSimulation_Chaos.cpp:92
Scope: file
Source code excerpt:
Chaos::FRealSingle ChaosImmediate_Joint_AngleTolerance = 0.001f;
int32 ChaosImmediate_Joint_NumShockPropagationIterations = -1;
int32 ChaosImmediate_Joint_SolvePositionLast = 1;
int32 ChaosImmediate_Joint_UsePositionBasedDrives = 1;
int32 ChaosImmediate_Joint_EnableTwistLimits = 1;
int32 ChaosImmediate_Joint_EnableSwingLimits = 1;
int32 ChaosImmediate_Joint_EnableDrives = 1;
Chaos::FRealSingle ChaosImmediate_Joint_LinearProjection = -1.0f;
Chaos::FRealSingle ChaosImmediate_Joint_AngularProjection = -1.0f;
#Loc: <Workspace>/Engine/Source/Runtime/Engine/Private/PhysicsEngine/ImmediatePhysics/ImmediatePhysicsChaos/ImmediatePhysicsSimulation_Chaos.cpp:116
Scope: file
Source code excerpt:
FAutoConsoleVariableRef CVarChaosImmPhysJointAngleTolerance(TEXT("p.Chaos.ImmPhys.Joint.AngleTolerance"), ChaosImmediate_Joint_AngleTolerance, TEXT("AngleTolerance."));
FAutoConsoleVariableRef CVarChaosImmPhysJointNumShockPropagationIterations(TEXT("p.Chaos.ImmPhys.Joint.NumShockPropagationIterations"), ChaosImmediate_Joint_NumShockPropagationIterations, TEXT("How many iterations to run shock propagation for"));
FAutoConsoleVariableRef CVarChaosImmPhysJointSolvePositionLast(TEXT("p.Chaos.ImmPhys.Joint.SolvePositionLast"), ChaosImmediate_Joint_SolvePositionLast, TEXT("Should we solve joints in position-then-rotation order (false) rotation-then-position order (true, default)"));
FAutoConsoleVariableRef CVarChaosImmPhysJointUsePBDVelocityDrives(TEXT("p.Chaos.ImmPhys.Joint.UsePBDDrives"), ChaosImmediate_Joint_UsePositionBasedDrives, TEXT("Whether to solve drives in the position or velocity phase of the solver (default true)"));
FAutoConsoleVariableRef CVarChaosImmPhysJointEnableTwistLimits(TEXT("p.Chaos.ImmPhys.Joint.EnableTwistLimits"), ChaosImmediate_Joint_EnableTwistLimits, TEXT("EnableTwistLimits."));
FAutoConsoleVariableRef CVarChaosImmPhysJointEnableSwingLimits(TEXT("p.Chaos.ImmPhys.Joint.EnableSwingLimits"), ChaosImmediate_Joint_EnableSwingLimits, TEXT("EnableSwingLimits."));
FAutoConsoleVariableRef CVarChaosImmPhysJointEnableDrives(TEXT("p.Chaos.ImmPhys.Joint.EnableDrives"), ChaosImmediate_Joint_EnableDrives, TEXT("EnableDrives."));
FAutoConsoleVariableRef CVarChaosImmPhysJointLinearProjection(TEXT("p.Chaos.ImmPhys.Joint.LinearProjection"), ChaosImmediate_Joint_LinearProjection, TEXT("6Dof joint projection amount override (if >= 0)."));
FAutoConsoleVariableRef CVarChaosImmPhysJointAngularProjection(TEXT("p.Chaos.ImmPhys.Joint.AngularProjection"), ChaosImmediate_Joint_AngularProjection, TEXT("6Dof joint projection amount override (if >= 0)."));
#Loc: <Workspace>/Engine/Source/Runtime/Engine/Private/PhysicsEngine/ImmediatePhysics/ImmediatePhysicsChaos/ImmediatePhysicsSimulation_Chaos.cpp:875
Scope (from outer to inner):
file
namespace ImmediatePhysics_Chaos
function void FSimulation::Simulate
Source code excerpt:
JointsSettings.MinParentMassRatio = ChaosImmediate_Joint_MinParentMassRatio;
JointsSettings.MaxInertiaRatio = ChaosImmediate_Joint_MaxInertiaRatio;
JointsSettings.bSolvePositionLast = ChaosImmediate_Joint_SolvePositionLast != 0;
JointsSettings.bUsePositionBasedDrives = ChaosImmediate_Joint_UsePositionBasedDrives != 0;
JointsSettings.bEnableTwistLimits = ChaosImmediate_Joint_EnableTwistLimits != 0;
JointsSettings.bEnableSwingLimits = ChaosImmediate_Joint_EnableSwingLimits != 0;
JointsSettings.bEnableDrives = ChaosImmediate_Joint_EnableDrives != 0;
JointsSettings.LinearStiffnessOverride = ChaosImmediate_Joint_Stiffness;
JointsSettings.TwistStiffnessOverride = ChaosImmediate_Joint_Stiffness;