#include <VehicleConstraint.h>

Inheritance diagram for VehicleConstraint:

Public Types
using	CombineFunction = function< void(uint inWheelIndex, float &ioLongitudinalFriction, float &ioLateralFriction, const Body &inBody2, const SubShapeID &inSubShapeID2)>

using	StepCallback = function< void(VehicleConstraint &inVehicle, float inDeltaTime, PhysicsSystem &inPhysicsSystem)>
	Callback function to notify of current stage in PhysicsStepListener::OnStep.

Public Member Functions
	VehicleConstraint (Body &inVehicleBody, const VehicleConstraintSettings &inSettings)
	Constructor / destructor.

virtual	~VehicleConstraint () override

virtual EConstraintSubType	GetSubType () const override
	Get the type of a constraint.

void	SetMaxPitchRollAngle (float inMaxPitchRollAngle)
	Defines the maximum pitch/roll angle (rad), can be used to avoid the car from getting upside down. The vehicle up direction will stay within a cone centered around the up axis with half top angle mMaxPitchRollAngle, set to pi to turn off.

void	SetVehicleCollisionTester (const VehicleCollisionTester *inTester)
	Set the interface that tests collision between wheel and ground.

void	SetCombineFriction (const CombineFunction &inCombineFriction)

const CombineFunction &	GetCombineFriction () const

const StepCallback &	GetPreStepCallback () const

void	SetPreStepCallback (const StepCallback &inPreStepCallback)

const StepCallback &	GetPostCollideCallback () const

void	SetPostCollideCallback (const StepCallback &inPostCollideCallback)

const StepCallback &	GetPostStepCallback () const

void	SetPostStepCallback (const StepCallback &inPostStepCallback)

Vec3	GetLocalForward () const
	Get the local space forward vector of the vehicle.

Vec3	GetLocalUp () const
	Get the local space up vector of the vehicle.

Vec3	GetWorldUp () const
	Vector indicating the world space up direction (used to limit vehicle pitch/roll), calculated every frame by inverting gravity.

Body *	GetVehicleBody () const
	Access to the vehicle body.

const VehicleController *	GetController () const
	Access to the vehicle controller interface (determines acceleration / deceleration)

VehicleController *	GetController ()
	Access to the vehicle controller interface (determines acceleration / deceleration)

const Wheels &	GetWheels () const
	Get the state of the wheels.

Wheels &	GetWheels ()
	Get the state of a wheels (writable interface, allows you to make changes to the configuration which will take effect the next time step)

Wheel *	GetWheel (uint inIdx)
	Get the state of a wheel.

const Wheel *	GetWheel (uint inIdx) const

void	GetWheelLocalBasis (const Wheel *inWheel, Vec3 &outForward, Vec3 &outUp, Vec3 &outRight) const

Mat44	GetWheelLocalTransform (uint inWheelIndex, Vec3Arg inWheelRight, Vec3Arg inWheelUp) const

RMat44	GetWheelWorldTransform (uint inWheelIndex, Vec3Arg inWheelRight, Vec3Arg inWheelUp) const

void	SetNumStepsBetweenCollisionTestActive (uint inSteps)

uint	GetNumStepsBetweenCollisionTestActive () const

void	SetNumStepsBetweenCollisionTestInactive (uint inSteps)

uint	GetNumStepsBetweenCollisionTestInactive () const

virtual bool	IsActive () const override

virtual void	NotifyShapeChanged (const BodyID &inBodyID, Vec3Arg inDeltaCOM) override

virtual void	SetupVelocityConstraint (float inDeltaTime) override

virtual void	ResetWarmStart () override

virtual void	WarmStartVelocityConstraint (float inWarmStartImpulseRatio) override

virtual bool	SolveVelocityConstraint (float inDeltaTime) override

virtual bool	SolvePositionConstraint (float inDeltaTime, float inBaumgarte) override

virtual void	BuildIslands (uint32 inConstraintIndex, IslandBuilder &ioBuilder, BodyManager &inBodyManager) override
	Link bodies that are connected by this constraint in the island builder.

virtual uint	BuildIslandSplits (LargeIslandSplitter &ioSplitter) const override
	Link bodies that are connected by this constraint in the same split. Returns the split index.

virtual void	DrawConstraint (DebugRenderer *inRenderer) const override

virtual void	DrawConstraintLimits (DebugRenderer *inRenderer) const override

virtual void	SaveState (StateRecorder &inStream) const override
	Saving state for replay.

virtual void	RestoreState (StateRecorder &inStream) override
	Restoring state for replay.

virtual Ref< ConstraintSettings >	GetConstraintSettings () const override
	Debug function to convert a constraint to its settings, note that this will not save to which bodies the constraint is connected to.

Public Member Functions inherited from Constraint
JPH_OVERRIDE_NEW_DELETE	Constraint (const ConstraintSettings &inSettings)
	Constructor.

virtual	~Constraint ()=default
	Virtual destructor.

virtual EConstraintType	GetType () const
	Get the type of a constraint.

uint32	GetConstraintPriority () const

void	SetConstraintPriority (uint32 inPriority)

void	SetNumVelocityStepsOverride (uint inN)
	Used only when the constraint is active. Override for the number of solver velocity iterations to run, 0 means use the default in PhysicsSettings::mNumVelocitySteps. The number of iterations to use is the max of all contacts and constraints in the island.

uint	GetNumVelocityStepsOverride () const

void	SetNumPositionStepsOverride (uint inN)
	Used only when the constraint is active. Override for the number of solver position iterations to run, 0 means use the default in PhysicsSettings::mNumPositionSteps. The number of iterations to use is the max of all contacts and constraints in the island.

uint	GetNumPositionStepsOverride () const

void	SetEnabled (bool inEnabled)

bool	GetEnabled () const
	Test if a constraint is enabled.

uint64	GetUserData () const
	Access to the user data, can be used for anything by the application.

void	SetUserData (uint64 inUserData)

virtual void	DrawConstraintReferenceFrame (DebugRenderer *inRenderer) const

float	GetDrawConstraintSize () const
	Size of constraint when drawing it through the debug renderer.

void	SetDrawConstraintSize (float inSize)

Public Member Functions inherited from RefTarget< Constraint >
	RefTarget ()=default
	Constructor.

	RefTarget (const RefTarget &)

	~RefTarget ()
	assert no one is referencing us

void	SetEmbedded () const

RefTarget &	operator= (const RefTarget &)
	Assignment operator.

uint32	GetRefCount () const
	Get current refcount of this object.

void	AddRef () const
	Add or release a reference to this object.

void	Release () const

Public Member Functions inherited from NonCopyable
	NonCopyable ()=default

	NonCopyable (const NonCopyable &)=delete

void	operator= (const NonCopyable &)=delete

Public Member Functions inherited from PhysicsStepListener
virtual	~PhysicsStepListener ()=default
	Ensure virtual destructor.

Additional Inherited Members
Static Public Member Functions inherited from RefTarget< Constraint >
static int	sInternalGetRefCountOffset ()
	INTERNAL HELPER FUNCTION USED BY SERIALIZATION.

Protected Member Functions inherited from Constraint
void	ToConstraintSettings (ConstraintSettings &outSettings) const
	Helper function to copy settings back to constraint settings for this base class.

Protected Attributes inherited from Constraint
float	mDrawConstraintSize
	Size of constraint when drawing it through the debug renderer.

Protected Attributes inherited from RefTarget< Constraint >
atomic< uint32 >	mRefCount
	Current reference count.

Static Protected Attributes inherited from RefTarget< Constraint >
static constexpr uint32	cEmbedded
	A large value that gets added to the refcount to mark the object as embedded.

Detailed Description

Constraint that simulates a vehicle Note: Don't forget to register the constraint as a StepListener with the PhysicsSystem!

When the vehicle drives over very light objects (rubble) you may see the car body dip down. This is a known issue and is an artifact of the iterative solver that Jolt is using. Basically if a light object is sandwiched between two heavy objects (the static floor and the car body), the light object is not able to transfer enough force from the ground to the car body to keep the car body up. You can see this effect in the HeavyOnLightTest sample, the boxes on the right have a lot of penetration because they're on top of light objects.

There are a couple of ways to improve this:

You can increase the number of velocity steps (global settings PhysicsSettings::mNumVelocitySteps or if you only want to increase it on the vehicle you can use VehicleConstraintSettings::mNumVelocityStepsOverride). E.g. going from 10 to 30 steps in the HeavyOnLightTest sample makes the penetration a lot less. The number of position steps can also be increased (the first prevents the body from going down, the second corrects it if the problem did occur which inevitably happens due to numerical drift). This solution costs CPU cycles.
You can reduce the mass difference between the vehicle body and the rubble on the floor (by making the rubble heavier or the car lighter).
You could filter out collisions between the vehicle collision test and the rubble completely. This would make the wheels ignore the rubble but would cause the vehicle to drive through it as if nothing happened. You could create fake wheels (keyframed bodies) that move along with the vehicle and that only collide with rubble (and not the vehicle or the ground). This would cause the vehicle to push away the rubble without the rubble being able to affect the vehicle (unless it hits the main body of course).

Note that when driving over rubble, you may see the wheel jump up and down quite quickly because one frame a collision is found and the next frame not. To alleviate this, it may be needed to smooth the motion of the visual mesh for the wheel.

Member Typedef Documentation

◆ CombineFunction

using VehicleConstraint::CombineFunction = function<void(uint inWheelIndex, float &ioLongitudinalFriction, float &ioLateralFriction, const Body &inBody2, const SubShapeID &inSubShapeID2)>

Callback function to combine the friction of a tire with the friction of the body it is colliding with. On input ioLongitudinalFriction and ioLateralFriction contain the friction of the tire, on output they should contain the combined friction with inBody2.

◆ StepCallback

using VehicleConstraint::StepCallback = function<void(VehicleConstraint &inVehicle, float inDeltaTime, PhysicsSystem &inPhysicsSystem)>

Callback function to notify of current stage in PhysicsStepListener::OnStep.

Constructor & Destructor Documentation

◆ VehicleConstraint()

VehicleConstraint::VehicleConstraint	(	Body &	inVehicleBody,
		const VehicleConstraintSettings &	inSettings
	)

Constructor / destructor.

◆ ~VehicleConstraint()

VehicleConstraint::~VehicleConstraint ( )

overridevirtual

Member Function Documentation

◆ BuildIslands()

void VehicleConstraint::BuildIslands	(	uint32	inConstraintIndex,
		IslandBuilder &	ioBuilder,
		BodyManager &	inBodyManager
	)

overridevirtual

Link bodies that are connected by this constraint in the island builder.

Implements Constraint.

◆ BuildIslandSplits()

uint VehicleConstraint::BuildIslandSplits ( LargeIslandSplitter & ioSplitter ) const

overridevirtual

Link bodies that are connected by this constraint in the same split. Returns the split index.

Implements Constraint.

◆ DrawConstraint()

void VehicleConstraint::DrawConstraint ( DebugRenderer * inRenderer ) const

overridevirtual

Implements Constraint.

◆ DrawConstraintLimits()

void VehicleConstraint::DrawConstraintLimits ( DebugRenderer * inRenderer ) const

overridevirtual

Reimplemented from Constraint.

◆ GetCombineFriction()

const CombineFunction & VehicleConstraint::GetCombineFriction ( ) const

inline

◆ GetConstraintSettings()

Ref< ConstraintSettings > VehicleConstraint::GetConstraintSettings ( ) const

overridevirtual

Debug function to convert a constraint to its settings, note that this will not save to which bodies the constraint is connected to.

Implements Constraint.

◆ GetController() [1/2]

VehicleController * VehicleConstraint::GetController ( )

inline

Access to the vehicle controller interface (determines acceleration / deceleration)

◆ GetController() [2/2]

const VehicleController * VehicleConstraint::GetController ( ) const

inline

Access to the vehicle controller interface (determines acceleration / deceleration)

◆ GetLocalForward()

Vec3 VehicleConstraint::GetLocalForward ( ) const

inline

Get the local space forward vector of the vehicle.

◆ GetLocalUp()

Vec3 VehicleConstraint::GetLocalUp ( ) const

inline

Get the local space up vector of the vehicle.

◆ GetNumStepsBetweenCollisionTestActive()

uint VehicleConstraint::GetNumStepsBetweenCollisionTestActive ( ) const

inline

◆ GetNumStepsBetweenCollisionTestInactive()

uint VehicleConstraint::GetNumStepsBetweenCollisionTestInactive ( ) const

inline

◆ GetPostCollideCallback()

const StepCallback & VehicleConstraint::GetPostCollideCallback ( ) const

inline

Callback function to notify that PhysicsStepListener::OnStep has just completed wheel collision checks. Default is to do nothing. Can be used to allow higher-level code to e.g. detect tire contact or to modify the velocity of the vehicle based on the wheel contacts. You should not change the position of the vehicle in this callback as the wheel collision checks have already been performed.

◆ GetPostStepCallback()

const StepCallback & VehicleConstraint::GetPostStepCallback ( ) const

inline

Callback function to notify that PhysicsStepListener::OnStep has completed for this vehicle. Default is to do nothing. Can be used to allow higher-level code to e.g. control the vehicle in the air. You should not change the position of the vehicle in this callback as the wheel collision checks have already been performed.

◆ GetPreStepCallback()

const StepCallback & VehicleConstraint::GetPreStepCallback ( ) const

inline

Callback function to notify that PhysicsStepListener::OnStep has started for this vehicle. Default is to do nothing. Can be used to allow higher-level code to e.g. control steering. This is the last moment that the position/orientation of the vehicle can be changed. Wheel collision checks have not been performed yet.

◆ GetSubType()

virtual EConstraintSubType VehicleConstraint::GetSubType ( ) const

inlineoverridevirtual

Get the type of a constraint.

Implements Constraint.

◆ GetVehicleBody()

Body * VehicleConstraint::GetVehicleBody ( ) const

inline

Access to the vehicle body.

◆ GetWheel() [1/2]

Wheel * VehicleConstraint::GetWheel ( uint inIdx )

inline

Get the state of a wheel.

◆ GetWheel() [2/2]

const Wheel * VehicleConstraint::GetWheel ( uint inIdx ) const

inline

◆ GetWheelLocalBasis()

void VehicleConstraint::GetWheelLocalBasis	(	const Wheel *	inWheel,
		Vec3 &	outForward,
		Vec3 &	outUp,
		Vec3 &	outRight
	)		const

Get the basis vectors for the wheel in local space to the vehicle body (note: basis does not rotate when the wheel rotates around its axis)

Parameters

inWheel	Wheel to fetch basis for
outForward	Forward vector for the wheel
outUp	Up vector for the wheel
outRight	Right vector for the wheel

◆ GetWheelLocalTransform()

Mat44 VehicleConstraint::GetWheelLocalTransform	(	uint	inWheelIndex,
		Vec3Arg	inWheelRight,
		Vec3Arg	inWheelUp
	)		const

Get the transform of a wheel in local space to the vehicle body, returns a matrix that transforms a cylinder aligned with the Y axis in body space (not COM space)

Parameters

inWheelIndex	Index of the wheel to fetch
inWheelRight	Unit vector that indicates right in model space of the wheel (so if you only have 1 wheel model, you probably want to specify the opposite direction for the left and right wheels)
inWheelUp	Unit vector that indicates up in model space of the wheel

◆ GetWheels() [1/2]

Wheels & VehicleConstraint::GetWheels ( )

inline

Get the state of a wheels (writable interface, allows you to make changes to the configuration which will take effect the next time step)

◆ GetWheels() [2/2]

const Wheels & VehicleConstraint::GetWheels ( ) const

inline

Get the state of the wheels.

◆ GetWheelWorldTransform()

RMat44 VehicleConstraint::GetWheelWorldTransform	(	uint	inWheelIndex,
		Vec3Arg	inWheelRight,
		Vec3Arg	inWheelUp
	)		const

Get the transform of a wheel in world space, returns a matrix that transforms a cylinder aligned with the Y axis in world space

Parameters

inWheelIndex	Index of the wheel to fetch
inWheelRight	Unit vector that indicates right in model space of the wheel (so if you only have 1 wheel model, you probably want to specify the opposite direction for the left and right wheels)
inWheelUp	Unit vector that indicates up in model space of the wheel

◆ GetWorldUp()

Vec3 VehicleConstraint::GetWorldUp ( ) const

inline

Vector indicating the world space up direction (used to limit vehicle pitch/roll), calculated every frame by inverting gravity.

◆ IsActive()

virtual bool VehicleConstraint::IsActive ( ) const

inlineoverridevirtual

Reimplemented from Constraint.

◆ NotifyShapeChanged()

virtual void VehicleConstraint::NotifyShapeChanged	(	const BodyID &	inBodyID,
		Vec3Arg	inDeltaCOM
	)

inlineoverridevirtual

Notify the constraint that the shape of a body has changed and that its center of mass has moved by inDeltaCOM. Bodies don't know which constraints are connected to them so the user is responsible for notifying the relevant constraints when a body changes.

Parameters

inBodyID	ID of the body that has changed
inDeltaCOM	The delta of the center of mass of the body (shape->GetCenterOfMass() - shape_before_change->GetCenterOfMass())

Implements Constraint.

◆ ResetWarmStart()

void VehicleConstraint::ResetWarmStart ( )

overridevirtual

Notify the system that the configuration of the bodies and/or constraint has changed enough so that the warm start impulses should not be applied the next frame. You can use this function for example when repositioning a ragdoll through Ragdoll::SetPose in such a way that the orientation of the bodies completely changes so that the previous frame impulses are no longer a good approximation of what the impulses will be in the next frame. Calling this function when there are no big changes will result in the constraints being much 'softer' than usual so they are more easily violated (e.g. a long chain of bodies might sag a bit if you call this every frame).

Implements Constraint.

◆ RestoreState()

void VehicleConstraint::RestoreState ( StateRecorder & inStream )

overridevirtual

Restoring state for replay.

Reimplemented from Constraint.

◆ SaveState()

void VehicleConstraint::SaveState ( StateRecorder & inStream ) const

overridevirtual

Saving state for replay.

Reimplemented from Constraint.

◆ SetCombineFriction()

void VehicleConstraint::SetCombineFriction ( const CombineFunction & inCombineFriction )

inline

Set the function that combines the friction of two bodies and returns it Default method is the geometric mean: sqrt(friction1 * friction2).

◆ SetMaxPitchRollAngle()

void VehicleConstraint::SetMaxPitchRollAngle ( float inMaxPitchRollAngle )

inline

Defines the maximum pitch/roll angle (rad), can be used to avoid the car from getting upside down. The vehicle up direction will stay within a cone centered around the up axis with half top angle mMaxPitchRollAngle, set to pi to turn off.

◆ SetNumStepsBetweenCollisionTestActive()

void VehicleConstraint::SetNumStepsBetweenCollisionTestActive ( uint inSteps )

inline

Number of simulation steps between wheel collision tests when the vehicle is active. Default is 1. 0 = never, 1 = every step, 2 = every other step, etc. Note that if a vehicle has multiple wheels and the number of steps > 1, the wheels will be tested in a round robin fashion. If there are multiple vehicles, the tests will be spread out based on the BodyID of the vehicle. If you set this to test less than every step, you may see simulation artifacts. This setting can be used to reduce the cost of simulating vehicles in the distance.

◆ SetNumStepsBetweenCollisionTestInactive()

void VehicleConstraint::SetNumStepsBetweenCollisionTestInactive ( uint inSteps )

inline

Number of simulation steps between wheel collision tests when the vehicle is inactive. Default is 1. 0 = never, 1 = every step, 2 = every other step, etc. Note that if a vehicle has multiple wheels and the number of steps > 1, the wheels will be tested in a round robin fashion. If there are multiple vehicles, the tests will be spread out based on the BodyID of the vehicle. This number can be lower than the number of steps when the vehicle is active as the only purpose of this test is to allow the vehicle to wake up in response to bodies moving into the wheels but not touching the body of the vehicle.

◆ SetPostCollideCallback()

void VehicleConstraint::SetPostCollideCallback ( const StepCallback & inPostCollideCallback )

inline

◆ SetPostStepCallback()

void VehicleConstraint::SetPostStepCallback ( const StepCallback & inPostStepCallback )

inline

◆ SetPreStepCallback()

void VehicleConstraint::SetPreStepCallback ( const StepCallback & inPreStepCallback )

inline

◆ SetupVelocityConstraint()

void VehicleConstraint::SetupVelocityConstraint ( float inDeltaTime )

overridevirtual

Implements Constraint.

◆ SetVehicleCollisionTester()

void VehicleConstraint::SetVehicleCollisionTester ( const VehicleCollisionTester * inTester )

inline

Set the interface that tests collision between wheel and ground.

◆ SolvePositionConstraint()

bool VehicleConstraint::SolvePositionConstraint	(	float	inDeltaTime,
		float	inBaumgarte
	)

overridevirtual

Implements Constraint.

◆ SolveVelocityConstraint()

bool VehicleConstraint::SolveVelocityConstraint ( float inDeltaTime )

overridevirtual

Implements Constraint.

◆ WarmStartVelocityConstraint()

void VehicleConstraint::WarmStartVelocityConstraint ( float inWarmStartImpulseRatio )

overridevirtual

Implements Constraint.

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

Jolt/Physics/Vehicle/VehicleConstraint.h
Jolt/Physics/Vehicle/VehicleConstraint.cpp

Public Types

Public Member Functions

Additional Inherited Members

Detailed Description

Member Typedef Documentation

◆ CombineFunction

◆ StepCallback

Constructor & Destructor Documentation

◆ VehicleConstraint()

◆ ~VehicleConstraint()

Member Function Documentation

◆ BuildIslands()

◆ BuildIslandSplits()

◆ DrawConstraint()

◆ DrawConstraintLimits()

◆ GetCombineFriction()

◆ GetConstraintSettings()

◆ GetController() [1/2]

◆ GetController() [2/2]

◆ GetLocalForward()

◆ GetLocalUp()

◆ GetNumStepsBetweenCollisionTestActive()

◆ GetNumStepsBetweenCollisionTestInactive()

◆ GetPostCollideCallback()

◆ GetPostStepCallback()

◆ GetPreStepCallback()

◆ GetSubType()

◆ GetVehicleBody()

◆ GetWheel() [1/2]

◆ GetWheel() [2/2]

◆ GetWheelLocalBasis()

◆ GetWheelLocalTransform()

◆ GetWheels() [1/2]

◆ GetWheels() [2/2]

◆ GetWheelWorldTransform()

◆ GetWorldUp()

◆ IsActive()

◆ NotifyShapeChanged()

◆ ResetWarmStart()

◆ RestoreState()

◆ SaveState()

◆ SetCombineFriction()

◆ SetMaxPitchRollAngle()

◆ SetNumStepsBetweenCollisionTestActive()

◆ SetNumStepsBetweenCollisionTestInactive()

◆ SetPostCollideCallback()

◆ SetPostStepCallback()

◆ SetPreStepCallback()

◆ SetupVelocityConstraint()

◆ SetVehicleCollisionTester()

◆ SolvePositionConstraint()

◆ SolveVelocityConstraint()

◆ WarmStartVelocityConstraint()