GearConstraintPart Class Reference

#include <GearConstraintPart.h>

Public Member Functions
void	CalculateConstraintProperties (const Body &inBody1, Vec3Arg inWorldSpaceHingeAxis1, const Body &inBody2, Vec3Arg inWorldSpaceHingeAxis2, float inRatio)
void	Deactivate ()
	Deactivate this constraint. More...
bool	IsActive () const
	Check if constraint is active. More...
void	WarmStart (Body &ioBody1, Body &ioBody2, float inWarmStartImpulseRatio)
bool	SolveVelocityConstraint (Body &ioBody1, Vec3Arg inWorldSpaceHingeAxis1, Body &ioBody2, Vec3Arg inWorldSpaceHingeAxis2, float inRatio)
float	GetTotalLambda () const
	Return lagrange multiplier. More...
bool	SolvePositionConstraint (Body &ioBody1, Body &ioBody2, float inC, float inBaumgarte) const
void	SaveState (StateRecorder &inStream) const
	Save state of this constraint part. More...
void	RestoreState (StateRecorder &inStream)
	Restore state of this constraint part. More...

Detailed Description

Constraint that constrains two rotations using a gear (rotating in opposite direction)

Constraint equation:

C = Rotation1(t) + r Rotation2(t)

Derivative:

d/dt C = 0 <=> w1 . a + r w2 . b = 0

Jacobian:

\[J = \begin{bmatrix}0 & a^T & 0 & r b^T\end{bmatrix}\]

Used terms (here and below, everything in world space):
a = axis around which body 1 rotates (normalized).
b = axis along which body 2 slides (normalized).
Rotation1(t) = rotation around a of body 1.
Rotation2(t) = rotation around b of body 2.
r = ratio between rotation for body 1 and 2.
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.
\(\beta\) = baumgarte constant.

Member Function Documentation

CalculateConstraintProperties()

void GearConstraintPart::CalculateConstraintProperties ( const Body &  inBody1, Vec3Arg  inWorldSpaceHingeAxis1, const Body &  inBody2, Vec3Arg  inWorldSpaceHingeAxis2, float  inRatio  )

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
inWorldSpaceHingeAxis1	The axis around which body 1 rotates
inWorldSpaceHingeAxis2	The axis around which body 2 rotates
inRatio	The ratio between rotation and translation

Deactivate()

void GearConstraintPart::Deactivate ( )

inline

Deactivate this constraint.

GetTotalLambda()

float GearConstraintPart::GetTotalLambda ( ) const

inline

Return lagrange multiplier.

IsActive()

bool GearConstraintPart::IsActive ( ) const

inline

Check if constraint is active.

RestoreState()

void GearConstraintPart::RestoreState ( StateRecorder &  inStream )

inline

Restore state of this constraint part.

SaveState()

void GearConstraintPart::SaveState ( StateRecorder &  inStream ) const

inline

Save state of this constraint part.

SolvePositionConstraint()

bool GearConstraintPart::SolvePositionConstraint ( Body &  ioBody1, Body &  ioBody2, 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
inC	Value of the constraint equation (C)
inBaumgarte	Baumgarte constant (fraction of the error to correct)

SolveVelocityConstraint()

bool GearConstraintPart::SolveVelocityConstraint ( Body &  ioBody1, Vec3Arg  inWorldSpaceHingeAxis1, Body &  ioBody2, Vec3Arg  inWorldSpaceHingeAxis2, float  inRatio  )

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
inWorldSpaceHingeAxis1	The axis around which body 1 rotates
inWorldSpaceHingeAxis2	The axis around which body 2 rotates
inRatio	The ratio between rotation and translation

WarmStart()

void GearConstraintPart::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/GearConstraintPart.h