PointConstraintPart Class Reference

#include <PointConstraintPart.h>

Public Member Functions
void	CalculateConstraintProperties (const Body &inBody1, Mat44Arg inRotation1, Vec3Arg inR1, const Body &inBody2, Mat44Arg inRotation2, Vec3Arg inR2)
void	Deactivate ()
	Deactivate this constraint.
bool	IsActive () const
	Check if constraint is active.
void	WarmStart (Body &ioBody1, Body &ioBody2, float inWarmStartImpulseRatio)
bool	SolveVelocityConstraint (Body &ioBody1, Body &ioBody2)
bool	SolvePositionConstraint (Body &ioBody1, Body &ioBody2, float inBaumgarte) const
Vec3	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

Constrains movement along 3 axis

See also

"Constraints Derivation for Rigid Body Simulation in 3D" - Daniel Chappuis, section 2.2.1

Constraint equation (eq 45):

\[C = p_2 - p_1\]

Jacobian (transposed) (eq 47):

\[J^T = \begin{bmatrix}-E & r1x & E & -r2x^T\end{bmatrix} = \begin{bmatrix}-E^T \\ r1x^T \\ E^T \\ -r2x^T\end{bmatrix} = \begin{bmatrix}-E \\ -r1x \\ E \\ r2x\end{bmatrix}\]

Used terms (here and below, everything in world space):
p1, p2 = constraint points.
r1 = p1 - x1.
r2 = p2 - x2.
r1x = 3x3 matrix for which r1x v = r1 x v (cross product).
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.
E = identity matrix.

Member Function Documentation

CalculateConstraintProperties()

void PointConstraintPart::CalculateConstraintProperties ( const Body & inBody1, Mat44Arg inRotation1, Vec3Arg inR1, const Body & inBody2, Mat44Arg inRotation2, Vec3Arg inR2 )

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
inRotation1	The 3x3 rotation matrix for body 1 (translation part is ignored)
inRotation2	The 3x3 rotation matrix for body 2 (translation part is ignored)
inR1	Local space vector from center of mass to constraint point for body 1
inR2	Local space vector from center of mass to constraint point for body 2

Deactivate()

void PointConstraintPart::Deactivate ( )

inline

Deactivate this constraint.

GetTotalLambda()

Vec3 PointConstraintPart::GetTotalLambda ( ) const

inline

Return lagrange multiplier.

IsActive()

bool PointConstraintPart::IsActive ( ) const

inline

Check if constraint is active.

RestoreState()

void PointConstraintPart::RestoreState ( StateRecorder & inStream )

inline

Restore state of this constraint part.

SaveState()

void PointConstraintPart::SaveState ( StateRecorder & inStream ) const

inline

Save state of this constraint part.

SolvePositionConstraint()

bool PointConstraintPart::SolvePositionConstraint ( Body & ioBody1, Body & ioBody2, 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
inBaumgarte	Baumgarte constant (fraction of the error to correct)

SolveVelocityConstraint()

bool PointConstraintPart::SolveVelocityConstraint ( Body & ioBody1, Body & ioBody2 )

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

WarmStart()

void PointConstraintPart::WarmStart ( Body & ioBody1, Body & ioBody2, 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
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/PointConstraintPart.h