p.Chaos.Solver.Joint.SolvePositionLast
p.Chaos.Solver.Joint.SolvePositionLast
#Overview
name: p.Chaos.Solver.Joint.SolvePositionLast
This variable is created as a Console Variable (cvar).
- type:
Var - help:
Should we solve joints in position-then-rotation order (false) or rotation-then-position order (true, default)
It is referenced in 3 C++ source files.
#Summary
#Usage in the C++ source code
The purpose of p.Chaos.Solver.Joint.SolvePositionLast is to determine the order in which joint constraints are solved in the Chaos physics solver of Unreal Engine 5. Specifically, it controls whether the solver should solve joint constraints in a position-then-rotation order (when set to false) or a rotation-then-position order (when set to true, which is the default).
This setting variable is primarily used in the Chaos physics system, which is part of Unreal Engine’s experimental physics simulation module. It’s specifically related to the joint solver within the Chaos system.
The value of this variable is set through the Unreal Engine console variable system, as evidenced by the FAutoConsoleVariableRef declaration in the code. This allows developers to adjust the behavior at runtime or through configuration files.
The associated variable bChaosSolverJointSolvePositionLast directly interacts with this setting. It’s used within the FPBDRigidsSolver class to configure the joint solver settings.
Developers should be aware that changing this variable will affect the behavior and potentially the stability of joint simulations in the Chaos physics system. The default value (true) solves rotation before position, which may be more suitable for certain types of simulations.
Best practices when using this variable include:
- Testing thoroughly when changing from the default value, as it can significantly impact joint behavior.
- Consider the specific requirements of your joint simulations when deciding whether to change this setting.
- Use in conjunction with other joint-related settings for fine-tuning physics behavior.
Regarding the associated variable bChaosSolverJointSolvePositionLast:
- Its purpose is to store and apply the setting within the Chaos solver implementation.
- It’s used directly in the FPBDRigidsSolver::PrepareAdvanceBy function to configure the joint solver settings.
- Its value is set based on the console variable p.Chaos.Solver.Joint.SolvePositionLast.
- Developers should treat this variable as read-only within their code, modifying the setting through the console variable instead.
#References in C++ code
#Callsites
This variable is referenced in the following C++ source code:
#Loc: <Workspace>/Engine/Source/Runtime/Experimental/Chaos/Private/PBDRigidsSolver.cpp:395
Scope (from outer to inner):
file
namespace Chaos
namespace CVars
Source code excerpt:
FAutoConsoleVariableRef CVarChaosSolverJointMaxSolverStiffness(TEXT("p.Chaos.Solver.Joint.MaxSolverStiffness"), ChaosSolverJointMaxSolverStiffness, TEXT("Solver stiffness on last iteration, increases each iteration from MinSolverStiffness."));
FAutoConsoleVariableRef CVarChaosSolverJointNumIterationsAtMaxSolverStiffness(TEXT("p.Chaos.Solver.Joint.NumIterationsAtMaxSolverStiffness"), ChaosSolverJointNumIterationsAtMaxSolverStiffness, TEXT("How many iterations we want at MaxSolverStiffness."));
FAutoConsoleVariableRef CVarChaosSolverJointSolvePositionFirst(TEXT("p.Chaos.Solver.Joint.SolvePositionLast"), bChaosSolverJointSolvePositionLast, TEXT("Should we solve joints in position-then-rotation order (false) or rotation-then-position order (true, default)"));
FAutoConsoleVariableRef CVarChaosSolverJointUsePBDVelocityDrives(TEXT("p.Chaos.Solver.Joint.UsePBDDrives"), bChaosSolverJointUsePositionBasedDrives, TEXT("Whether to solve drives in the position or velocity phase of the solver (default true"));
FAutoConsoleVariableRef CVarChaosSolverJointNumShockPropagationIterations(TEXT("p.Chaos.Solver.Joint.NumShockPropagationIterations"), ChaosSolverJointNumShockProagationIterations, TEXT("How many iterations to enable SHockProagation for."));
FAutoConsoleVariableRef CVarChaosSolverJointShockPropagation(TEXT("p.Chaos.Solver.Joint.ShockPropagation"), ChaosSolverJointShockPropagation, TEXT("6Dof joint shock propagation override (if >= 0)."));
int32 ChaosVisualDebuggerEnable = 1;
FAutoConsoleVariableRef CVarChaosVisualDebuggerEnable(TEXT("p.Chaos.VisualDebuggerEnable"), ChaosVisualDebuggerEnable, TEXT("Enable/Disable pushing/saving data to the visual debugger"));
#Associated Variable and Callsites
This variable is associated with another variable named bChaosSolverJointSolvePositionLast. They share the same value. See the following C++ source code.
#Loc: <Workspace>/Engine/Source/Runtime/Experimental/Chaos/Private/PBDRigidsSolver.cpp:388
Scope (from outer to inner):
file
namespace Chaos
namespace CVars
Source code excerpt:
float ChaosSolverJointMaxSolverStiffness = 1.0f;
int32 ChaosSolverJointNumIterationsAtMaxSolverStiffness = 1;
bool bChaosSolverJointSolvePositionLast = true;
bool bChaosSolverJointUsePositionBasedDrives = true;
int32 ChaosSolverJointNumShockProagationIterations = 0;
FRealSingle ChaosSolverJointShockPropagation = -1.0f;
FAutoConsoleVariableRef CVarChaosSolverJointMinSolverStiffness(TEXT("p.Chaos.Solver.Joint.MinSolverStiffness"), ChaosSolverJointMinSolverStiffness, TEXT("Solver stiffness on first iteration, increases each iteration toward MaxSolverStiffness."));
FAutoConsoleVariableRef CVarChaosSolverJointMaxSolverStiffness(TEXT("p.Chaos.Solver.Joint.MaxSolverStiffness"), ChaosSolverJointMaxSolverStiffness, TEXT("Solver stiffness on last iteration, increases each iteration from MinSolverStiffness."));
FAutoConsoleVariableRef CVarChaosSolverJointNumIterationsAtMaxSolverStiffness(TEXT("p.Chaos.Solver.Joint.NumIterationsAtMaxSolverStiffness"), ChaosSolverJointNumIterationsAtMaxSolverStiffness, TEXT("How many iterations we want at MaxSolverStiffness."));
FAutoConsoleVariableRef CVarChaosSolverJointSolvePositionFirst(TEXT("p.Chaos.Solver.Joint.SolvePositionLast"), bChaosSolverJointSolvePositionLast, TEXT("Should we solve joints in position-then-rotation order (false) or rotation-then-position order (true, default)"));
FAutoConsoleVariableRef CVarChaosSolverJointUsePBDVelocityDrives(TEXT("p.Chaos.Solver.Joint.UsePBDDrives"), bChaosSolverJointUsePositionBasedDrives, TEXT("Whether to solve drives in the position or velocity phase of the solver (default true"));
FAutoConsoleVariableRef CVarChaosSolverJointNumShockPropagationIterations(TEXT("p.Chaos.Solver.Joint.NumShockPropagationIterations"), ChaosSolverJointNumShockProagationIterations, TEXT("How many iterations to enable SHockProagation for."));
FAutoConsoleVariableRef CVarChaosSolverJointShockPropagation(TEXT("p.Chaos.Solver.Joint.ShockPropagation"), ChaosSolverJointShockPropagation, TEXT("6Dof joint shock propagation override (if >= 0)."));
int32 ChaosVisualDebuggerEnable = 1;
FAutoConsoleVariableRef CVarChaosVisualDebuggerEnable(TEXT("p.Chaos.VisualDebuggerEnable"), ChaosVisualDebuggerEnable, TEXT("Enable/Disable pushing/saving data to the visual debugger"));
#Loc: <Workspace>/Engine/Source/Runtime/Experimental/Chaos/Private/PBDRigidsSolver.cpp:1299
Scope (from outer to inner):
file
namespace Chaos
function void FPBDRigidsSolver::PrepareAdvanceBy
Source code excerpt:
JointsSettings.MinParentMassRatio = ChaosSolverJointMinParentMassRatio;
JointsSettings.MaxInertiaRatio = ChaosSolverJointMaxInertiaRatio;
JointsSettings.bSolvePositionLast = bChaosSolverJointSolvePositionLast;
JointsSettings.bUsePositionBasedDrives = bChaosSolverJointUsePositionBasedDrives;
JointsSettings.NumShockPropagationIterations = ChaosSolverJointNumShockProagationIterations;
JointsSettings.ShockPropagationOverride = ChaosSolverJointShockPropagation;
JointsSettings.bUseLinearSolver = bChaosSolverJointUseLinearSolver;
JointsSettings.bSortEnabled = false;
MEvolution->GetJointConstraints().SetSettings(JointsSettings);