AxisConstraintPart Class Reference

#include <AxisConstraintPart.h>

Public Member Functions
template<EMotionType Type1, EMotionType Type2>
JPH_INLINE void	TemplatedCalculateConstraintProperties (float inInvMass1, Mat44Arg inInvI1, Vec3Arg inR1PlusU, float inInvMass2, Mat44Arg inInvI2, Vec3Arg inR2, Vec3Arg inWorldSpaceAxis, float inBias=0.0f)
	Templated form of CalculateConstraintProperties with the motion types baked in.
void	CalculateConstraintProperties (const Body &inBody1, Vec3Arg inR1PlusU, const Body &inBody2, Vec3Arg inR2, Vec3Arg inWorldSpaceAxis, float inBias=0.0f)
void	CalculateConstraintPropertiesWithMassOverride (const Body &inBody1, float inInvMass1, float inInvInertiaScale1, Vec3Arg inR1PlusU, const Body &inBody2, float inInvMass2, float inInvInertiaScale2, Vec3Arg inR2, Vec3Arg inWorldSpaceAxis, float inBias=0.0f)
void	CalculateConstraintPropertiesWithFrequencyAndDamping (float inDeltaTime, const Body &inBody1, Vec3Arg inR1PlusU, const Body &inBody2, Vec3Arg inR2, Vec3Arg inWorldSpaceAxis, float inBias, float inC, float inFrequency, float inDamping)
void	CalculateConstraintPropertiesWithStiffnessAndDamping (float inDeltaTime, const Body &inBody1, Vec3Arg inR1PlusU, const Body &inBody2, Vec3Arg inR2, Vec3Arg inWorldSpaceAxis, float inBias, float inC, float inStiffness, float inDamping)
void	CalculateConstraintPropertiesWithSettings (float inDeltaTime, const Body &inBody1, Vec3Arg inR1PlusU, const Body &inBody2, Vec3Arg inR2, Vec3Arg inWorldSpaceAxis, float inBias, float inC, const SpringSettings &inSpringSettings)
	Selects one of the above functions based on the spring settings.
void	Deactivate ()
	Deactivate this constraint.
bool	IsActive () const
	Check if constraint is active.
template<EMotionType Type1, EMotionType Type2>
void	TemplatedWarmStart (MotionProperties *ioMotionProperties1, float inInvMass1, MotionProperties *ioMotionProperties2, float inInvMass2, Vec3Arg inWorldSpaceAxis, float inWarmStartImpulseRatio)
	Templated form of WarmStart with the motion types baked in.
void	WarmStart (Body &ioBody1, Body &ioBody2, Vec3Arg inWorldSpaceAxis, float inWarmStartImpulseRatio)
template<EMotionType Type1, EMotionType Type2>
JPH_INLINE float	TemplatedSolveVelocityConstraintGetTotalLambda (const MotionProperties *ioMotionProperties1, const MotionProperties *ioMotionProperties2, Vec3Arg inWorldSpaceAxis) const
	Templated form of SolveVelocityConstraint with the motion types baked in, part 1: get the total lambda.
template<EMotionType Type1, EMotionType Type2>
JPH_INLINE bool	TemplatedSolveVelocityConstraintApplyLambda (MotionProperties *ioMotionProperties1, float inInvMass1, MotionProperties *ioMotionProperties2, float inInvMass2, Vec3Arg inWorldSpaceAxis, float inTotalLambda)
	Templated form of SolveVelocityConstraint with the motion types baked in, part 2: apply new lambda.
template<EMotionType Type1, EMotionType Type2>
bool	TemplatedSolveVelocityConstraint (MotionProperties *ioMotionProperties1, float inInvMass1, MotionProperties *ioMotionProperties2, float inInvMass2, Vec3Arg inWorldSpaceAxis, float inMinLambda, float inMaxLambda)
	Templated form of SolveVelocityConstraint with the motion types baked in.
bool	SolveVelocityConstraint (Body &ioBody1, Body &ioBody2, Vec3Arg inWorldSpaceAxis, float inMinLambda, float inMaxLambda)
bool	SolveVelocityConstraintWithMassOverride (Body &ioBody1, float inInvMass1, Body &ioBody2, float inInvMass2, Vec3Arg inWorldSpaceAxis, float inMinLambda, float inMaxLambda)
bool	SolvePositionConstraint (Body &ioBody1, Body &ioBody2, Vec3Arg inWorldSpaceAxis, float inC, float inBaumgarte) const
bool	SolvePositionConstraintWithMassOverride (Body &ioBody1, float inInvMass1, Body &ioBody2, float inInvMass2, Vec3Arg inWorldSpaceAxis, float inC, float inBaumgarte) const
void	SetTotalLambda (float inLambda)
	Override total lagrange multiplier, can be used to set the initial value for warm starting.
float	GetTotalLambda () const
	Return lagrange multiplier.
void	SaveState (StateRecorder &inStream) const
	Save state of this constraint part.
void	RestoreState (StateRecorder &inStream)
	Restore state of this constraint part.

Detailed Description

Constraint that constrains motion along 1 axis

See also

"Constraints Derivation for Rigid Body Simulation in 3D" - Daniel Chappuis, section 2.1.1 (we're not using the approximation of eq 27 but instead add the U term as in eq 55)

Constraint equation (eq 25):

\[C = (p_2 - p_1) \cdot n\]

Jacobian (eq 28):

\[J = \begin{bmatrix} -n^T & (-(r_1 + u) \times n)^T & n^T & (r_2 \times n)^T \end{bmatrix}\]

Used terms (here and below, everything in world space):
n = constraint axis (normalized).
p1, p2 = constraint points.
r1 = p1 - x1.
r2 = p2 - x2.
u = x2 + r2 - x1 - r1 = p2 - p1.
x1, x2 = center of mass for the bodies.
v = [v1, w1, v2, w2].
v1, v2 = linear velocity of body 1 and 2.
w1, w2 = angular velocity of body 1 and 2.
M = mass matrix, a diagonal matrix of the mass and inertia with diagonal [m1, I1, m2, I2].
\(K^{-1} = \left( J M^{-1} J^T \right)^{-1}\) = effective mass.
b = velocity bias.
\(\beta\) = baumgarte constant.

Member Function Documentation

CalculateConstraintProperties()

void AxisConstraintPart::CalculateConstraintProperties ( const Body & inBody1, Vec3Arg inR1PlusU, const Body & inBody2, Vec3Arg inR2, Vec3Arg inWorldSpaceAxis, float inBias = 0.0f )

inline

Calculate properties used during the functions below

Parameters

inBody1	The first body that this constraint is attached to
inBody2	The second body that this constraint is attached to
inR1PlusU	See equations above (r1 + u)
inR2	See equations above (r2)
inWorldSpaceAxis	Axis along which the constraint acts (normalized, pointing from body 1 to 2)
inBias	Bias term (b) for the constraint impulse: lambda = J v + b

CalculateConstraintPropertiesWithFrequencyAndDamping()

void AxisConstraintPart::CalculateConstraintPropertiesWithFrequencyAndDamping ( float inDeltaTime, const Body & inBody1, Vec3Arg inR1PlusU, const Body & inBody2, Vec3Arg inR2, Vec3Arg inWorldSpaceAxis, float inBias, float inC, float inFrequency, float inDamping )

inline

Calculate properties used during the functions below

Parameters

inDeltaTime	Time step
inBody1	The first body that this constraint is attached to
inBody2	The second body that this constraint is attached to
inR1PlusU	See equations above (r1 + u)
inR2	See equations above (r2)
inWorldSpaceAxis	Axis along which the constraint acts (normalized, pointing from body 1 to 2)
inBias	Bias term (b) for the constraint impulse: lambda = J v + b
inC	Value of the constraint equation (C).
inFrequency	Oscillation frequency (Hz).
inDamping	Damping factor (0 = no damping, 1 = critical damping).

CalculateConstraintPropertiesWithMassOverride()

void AxisConstraintPart::CalculateConstraintPropertiesWithMassOverride ( const Body & inBody1, float inInvMass1, float inInvInertiaScale1, Vec3Arg inR1PlusU, const Body & inBody2, float inInvMass2, float inInvInertiaScale2, Vec3Arg inR2, Vec3Arg inWorldSpaceAxis, float inBias = 0.0f )

inline

Calculate properties used during the functions below, version that supports mass scaling

Parameters

inBody1	The first body that this constraint is attached to
inBody2	The second body that this constraint is attached to
inInvMass1	The inverse mass of body 1 (only used when body 1 is dynamic)
inInvMass2	The inverse mass of body 2 (only used when body 2 is dynamic)
inInvInertiaScale1	Scale factor for the inverse inertia of body 1
inInvInertiaScale2	Scale factor for the inverse inertia of body 2
inR1PlusU	See equations above (r1 + u)
inR2	See equations above (r2)
inWorldSpaceAxis	Axis along which the constraint acts (normalized, pointing from body 1 to 2)
inBias	Bias term (b) for the constraint impulse: lambda = J v + b

CalculateConstraintPropertiesWithSettings()

void AxisConstraintPart::CalculateConstraintPropertiesWithSettings ( float inDeltaTime, const Body & inBody1, Vec3Arg inR1PlusU, const Body & inBody2, Vec3Arg inR2, Vec3Arg inWorldSpaceAxis, float inBias, float inC, const SpringSettings & inSpringSettings )

inline

Selects one of the above functions based on the spring settings.

CalculateConstraintPropertiesWithStiffnessAndDamping()

void AxisConstraintPart::CalculateConstraintPropertiesWithStiffnessAndDamping ( float inDeltaTime, const Body & inBody1, Vec3Arg inR1PlusU, const Body & inBody2, Vec3Arg inR2, Vec3Arg inWorldSpaceAxis, float inBias, float inC, float inStiffness, float inDamping )

inline

Calculate properties used during the functions below

Parameters

inDeltaTime	Time step
inBody1	The first body that this constraint is attached to
inBody2	The second body that this constraint is attached to
inR1PlusU	See equations above (r1 + u)
inR2	See equations above (r2)
inWorldSpaceAxis	Axis along which the constraint acts (normalized, pointing from body 1 to 2)
inBias	Bias term (b) for the constraint impulse: lambda = J v + b
inC	Value of the constraint equation (C).
inStiffness	Spring stiffness k.
inDamping	Spring damping coefficient c.

Deactivate()

void AxisConstraintPart::Deactivate ( )

inline

Deactivate this constraint.

GetTotalLambda()

float AxisConstraintPart::GetTotalLambda ( ) const

inline

Return lagrange multiplier.

IsActive()

bool AxisConstraintPart::IsActive ( ) const

inline

Check if constraint is active.

RestoreState()

void AxisConstraintPart::RestoreState ( StateRecorder & inStream )

inline

Restore state of this constraint part.

SaveState()

void AxisConstraintPart::SaveState ( StateRecorder & inStream ) const

inline

Save state of this constraint part.

SetTotalLambda()

void AxisConstraintPart::SetTotalLambda ( float inLambda )

inline

Override total lagrange multiplier, can be used to set the initial value for warm starting.

SolvePositionConstraint()

bool AxisConstraintPart::SolvePositionConstraint ( Body & ioBody1, Body & ioBody2, Vec3Arg inWorldSpaceAxis, float inC, float inBaumgarte ) const

inline

Iteratively update the position constraint. Makes sure C(...) = 0.

Parameters

ioBody1	The first body that this constraint is attached to
ioBody2	The second body that this constraint is attached to
inWorldSpaceAxis	Axis along which the constraint acts (normalized)
inC	Value of the constraint equation (C)
inBaumgarte	Baumgarte constant (fraction of the error to correct)

SolvePositionConstraintWithMassOverride()

bool AxisConstraintPart::SolvePositionConstraintWithMassOverride ( Body & ioBody1, float inInvMass1, Body & ioBody2, float inInvMass2, Vec3Arg inWorldSpaceAxis, float inC, float inBaumgarte ) const

inline

Iteratively update the position constraint. Makes sure C(...) = 0.

Parameters

ioBody1	The first body that this constraint is attached to
ioBody2	The second body that this constraint is attached to
inInvMass1	The inverse mass of body 1 (only used when body 1 is dynamic)
inInvMass2	The inverse mass of body 2 (only used when body 2 is dynamic)
inWorldSpaceAxis	Axis along which the constraint acts (normalized)
inC	Value of the constraint equation (C)
inBaumgarte	Baumgarte constant (fraction of the error to correct)

SolveVelocityConstraint()

bool AxisConstraintPart::SolveVelocityConstraint ( Body & ioBody1, Body & ioBody2, Vec3Arg inWorldSpaceAxis, float inMinLambda, float inMaxLambda )

inline

Iteratively update the velocity constraint. Makes sure d/dt C(...) = 0, where C is the constraint equation.

Parameters

ioBody1	The first body that this constraint is attached to
ioBody2	The second body that this constraint is attached to
inWorldSpaceAxis	Axis along which the constraint acts (normalized)
inMinLambda	Minimum value of constraint impulse to apply (N s)
inMaxLambda	Maximum value of constraint impulse to apply (N s)

SolveVelocityConstraintWithMassOverride()

bool AxisConstraintPart::SolveVelocityConstraintWithMassOverride ( Body & ioBody1, float inInvMass1, Body & ioBody2, float inInvMass2, Vec3Arg inWorldSpaceAxis, float inMinLambda, float inMaxLambda )

inline

Iteratively update the velocity constraint. Makes sure d/dt C(...) = 0, where C is the constraint equation.

Parameters

ioBody1	The first body that this constraint is attached to
ioBody2	The second body that this constraint is attached to
inInvMass1	The inverse mass of body 1 (only used when body 1 is dynamic)
inInvMass2	The inverse mass of body 2 (only used when body 2 is dynamic)
inWorldSpaceAxis	Axis along which the constraint acts (normalized)
inMinLambda	Minimum value of constraint impulse to apply (N s)
inMaxLambda	Maximum value of constraint impulse to apply (N s)

TemplatedCalculateConstraintProperties()

template<EMotionType Type1, EMotionType Type2>

JPH_INLINE void AxisConstraintPart::TemplatedCalculateConstraintProperties ( float inInvMass1, Mat44Arg inInvI1, Vec3Arg inR1PlusU, float inInvMass2, Mat44Arg inInvI2, Vec3Arg inR2, Vec3Arg inWorldSpaceAxis, float inBias = 0.0f )

inline

Templated form of CalculateConstraintProperties with the motion types baked in.

TemplatedSolveVelocityConstraint()

template<EMotionType Type1, EMotionType Type2>

bool AxisConstraintPart::TemplatedSolveVelocityConstraint ( MotionProperties * ioMotionProperties1, float inInvMass1, MotionProperties * ioMotionProperties2, float inInvMass2, Vec3Arg inWorldSpaceAxis, float inMinLambda, float inMaxLambda )

inline

Templated form of SolveVelocityConstraint with the motion types baked in.

TemplatedSolveVelocityConstraintApplyLambda()

template<EMotionType Type1, EMotionType Type2>

JPH_INLINE bool AxisConstraintPart::TemplatedSolveVelocityConstraintApplyLambda ( MotionProperties * ioMotionProperties1, float inInvMass1, MotionProperties * ioMotionProperties2, float inInvMass2, Vec3Arg inWorldSpaceAxis, float inTotalLambda )

inline

Templated form of SolveVelocityConstraint with the motion types baked in, part 2: apply new lambda.

TemplatedSolveVelocityConstraintGetTotalLambda()

template<EMotionType Type1, EMotionType Type2>

JPH_INLINE float AxisConstraintPart::TemplatedSolveVelocityConstraintGetTotalLambda ( const MotionProperties * ioMotionProperties1, const MotionProperties * ioMotionProperties2, Vec3Arg inWorldSpaceAxis ) const

inline

Templated form of SolveVelocityConstraint with the motion types baked in, part 1: get the total lambda.

TemplatedWarmStart()

template<EMotionType Type1, EMotionType Type2>

void AxisConstraintPart::TemplatedWarmStart ( MotionProperties * ioMotionProperties1, float inInvMass1, MotionProperties * ioMotionProperties2, float inInvMass2, Vec3Arg inWorldSpaceAxis, float inWarmStartImpulseRatio )

inline

Templated form of WarmStart with the motion types baked in.

WarmStart()

void AxisConstraintPart::WarmStart ( Body & ioBody1, Body & ioBody2, Vec3Arg inWorldSpaceAxis, float inWarmStartImpulseRatio )

inline

Must be called from the WarmStartVelocityConstraint call to apply the previous frame's impulses

Parameters

ioBody1	The first body that this constraint is attached to
ioBody2	The second body that this constraint is attached to
inWorldSpaceAxis	Axis along which the constraint acts (normalized)
inWarmStartImpulseRatio	Ratio of new step to old time step (dt_new / dt_old) for scaling the lagrange multiplier of the previous frame

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The documentation for this class was generated from the following file:

• Jolt/Physics/Constraints/ConstraintPart/AxisConstraintPart.h