GravityState Class Reference

Gravity state. Hold "most" of the information for gravitational evolution of the system. More...

Classes
struct	NbodyState

Public Types
enum	Evolvers { MASSIVE , FIXED , PARTICLES }
	physical time per evolver since start OR last timescale change

Public Member Functions
	GravityState (int size)
	New Gravity state. Also need to call SetAlgorithmAndForce to fully configure.
	GravityState (GravityState fromState)
	Clone constructor.
NbodyState[]	GetNbodyStates ()
void	SetAlgorithmAndForce (GravityEngine.Algorithm algorithm, IForceDelegate forceDelegate)
	Set the integrator required for the chosen algorithm.
void	InitArrays (int arraySize)
bool	GrowArrays (int growBy)
void	Clear ()
void	ResetPhysicalTime ()
void	AddFixedBody (GravityEngine ge, int index, GravityEngine.FixedBody fixedBody, IFixedOrbit fixedOrbit)
void	RemoveFixedBody (NBody nbody)
void	UpdateKeplerDepth (NBody nbody, OrbitUniversal orbitU)
	Recompute and update the kepler depth of a fixed body.
void	AddNBody (NBody nbody, float massScale, float physToWorldFactor, bool isFixed)
void	RemoveNBody (NBody nbody)
	Remove the body at index and shuffle up the rest. Ensure the integrator does the same to stay in alignment.
void	UpdateOnRails ()
	Check if all bodies are on rails.
void	PreEvolve (GravityEngine ge)
bool	IsOnRails ()
	Are all bodies in the world state "on-rails"?
bool	Evolve (GravityEngine ge, double timeStep)
	Evolve the objects subject to gravity.
bool	EvolveReversed (GravityEngine ge, double timeStep)
void	MoveFixedBodies (double time)
void	EvolveForTimestepReversed (GravityEngine ge, double physicsDt, bool exactTime=false)
	Evolve backwards.
Vector3	GetPhysicsPosition (NBody nbody)
	Get the internal position used by the physics engine.
Vector3d	GetPhysicsPositionDoubleV3 (NBody nbody)
Vector3d	GetPhysicsPositionDouble (NBody nbody)
	Get the internal position used by the physics engine.
void	GetVelocityDouble (NBody nbody, ref double[] vel)
	Get the physics velocity for an NBody as a double[].
Vector3d	GetVelocity3d (NBody nbody)
void	UpdatePositionAndVelocity (NBody nbody, Vector3d pos, Vector3d vel, Maneuver m=null)
void	SetVelocityDouble (NBody nbody, ref double[] velocity)
	Set the physics velocity from a double array.
void	SetVelocity3d (NBody nbody, Vector3d velocity)
void	UpdateInternalDouble (NBody nbody, Vector3d pos, Vector3d velocity)
	Internal use only from OrbitUniversal InitFromRVT Ensures cached state is current so can use info prior to the next Evolve call.
void	SetPosition3d (NBody nbody, Vector3d pos)
	Set the physics velocity from a double array.
double	GetMass (NBody nbody)
	Return the internal physics engine mass.
double	GetPhysicsTime ()
	Get the internal physics time for massive bodies.
void	SetTime (double newTime, bool force)
void	EvolveToTime (double newTime)
	Evolve all bodies to the new time (past or future). This will trigger a integration sequence when there is at least one body off rails and this may cause a burst of CPU activity if the time delta is large.
void	ApplyChangeAtTime (NBody nbody, double atTime, Vector3d r, Vector3d v)
	Apply a change in R,V to an NBody object in the past or future.
void	ReverseVelocities ()
GERewindMgr	GetGERewindMgr ()
bool	NbodyIsActive (NBody nbody)
bool	NbodyIndexIsActive (int index)
void	NbodySetIsActive (NBody nbody, bool state)
void	NbodySetNoUpdateFlag (NBody nbody, bool state)
bool	NbodyGetNoUpdateFlag (NBody nbody)
bool	NbodyGetNoUpdateFlag (int index)
bool	NbodyIsFixed (NBody nbody)
void	NbodySetIsFixed (NBody nbody, bool state)
void	SetMass (NBody nbody, double mass)
void	SetSize2 (NBody nbody, double size)
void	AddTrigger (GETriggerMgr.Trigger t)
void	RemoveTrigger (GETriggerMgr.Trigger t)
void	ClearTriggers ()
string	DumpAll (NBody[] gameNBodies, GravityEngine ge)
Vector3d	ComputeCenterOfMass ()
	Deterimine the center of mass.
Vector3d	ComputeCenterOfMassVelocity ()
	Compute the velocity of the CM. Consider only massive bodies. If there are any FixedObject elements they will be weighted with a velocity of zero.
void	SetCenterOfMass (GravityEngine ge, Vector3d pos, Vector3d vel)
	Set the CM to the specified postion and velocity.
void	MoveAll (Vector3d moveBy)

Public Attributes
int	numBodies
List< GravityEngine.FixedBody >	fixedBodies
int	arraySize
	size of the arrays (may exceed the number of bodies due to pre-allocation)
double	time
	time of current state (in the engine physics time)
bool	hasTrajectories
	State has trajectories that require updating.
double[]	physicalTime
bool	isAsync
	Flag to indicate running async (on a non-main thread). If true, cannot do debug logging or access scene.
INBodyIntegrator	integrator
List< GravityParticles >	gravityParticles
ManeuverMgr	maneuverMgr
bool	isCopy

Static Public Attributes
const int	NDIM = 3

Protected Attributes
NbodyState[]	nbodyStates

Detailed Description

Gravity state. Hold "most" of the information for gravitational evolution of the system.

The NBody objects added can be massive or massless. They can independently be in normal gravitational motion or have their motion FIXED in some way (either by a Kepler/on-rail evolution mode or simply being not movable).

Massive bodies are tracked here by the arrays m[] and r[]. These arrays are then updated by passing to the selected numerical integrator. This allows a central object manager to compute the mutual gravitational interactions in the most effecient way. Each fixed frame the r[] value are copied back to the transform positions of the associated game objects (this is done in the GE class).

A parallel list of FixedBodies is maintained BUT they are also in the r[] list, since their masses may affect non-fixed bodies.

Massless bodies are evolved seperately using a simple Leapfrog integrator (unless Optimize Massless has been set to false).

Particles are always evolved seperately using a simpe Leapfrog integrator.

A scene may have more than one gravity state. Additional copies may be used for trajectory prediction, to determine future paths objects will take.

Constructor & Destructor Documentation

GravityState() [1/2]

GravityState.GravityState

(

int

size

)

New Gravity state. Also need to call SetAlgorithmAndForce to fully configure.

Parameters

size

GravityState() [2/2]

GravityState.GravityState

(

GravityState

fromState

)

Clone constructor.

Creates a deep copy suitable for independent evolution as a trajectory or for maneuver iterations. Maneuvers will be executed but the callback to motify the owner of the maneuver will be skipped (only the real evolution will notify).

Parameters

fromState

Member Function Documentation

ApplyChangeAtTime()

void GravityState.ApplyChangeAtTime	(	NBody	nbody,
		double	atTime,
		Vector3d	r,
		Vector3d	v
	)

Apply a change in R,V to an NBody object in the past or future.

The intended use is to allow an update that has experienced network delay to be applied at an earlier point in the simulation to facilitate a distributed lockstep mode for multiplayer games.

Parameters

rewindTime
r
v

ComputeCenterOfMass()

Vector3d GravityState.ComputeCenterOfMass

(

)

Deterimine the center of mass.

Returns

ComputeCenterOfMassVelocity()

Vector3d GravityState.ComputeCenterOfMassVelocity

(

)

Compute the velocity of the CM. Consider only massive bodies. If there are any FixedObject elements they will be weighted with a velocity of zero.

Returns

Evolve()

bool GravityState.Evolve	(	GravityEngine	ge,
		double	timeStep
	)

Evolve the objects subject to gravity.

Normal evolution is done by passing in worldState with a time interval corresponding to the frame advance time multiplied by the time zoom.

For trajectory updates in the case where the trajectory is up to date, this will be for the same interval but starting at a future time.

In order for trajectory computation to "catch up", there are times when the interval may be longer (but limited by the re-compute factor to avoid a huge recomputation on a single frame).

Maneuvers are ONLY added to the world state, so code in the trajectory state will not encounter maneuvers.

Parameters

ge	The Gravity engine
timeStep	The amount of physics DT to be evolved

EvolveForTimestepReversed()

void GravityState.EvolveForTimestepReversed	(	GravityEngine	ge,
		double	physicsDt,
		bool	exactTime = false
	)

Evolve backwards.

• when there are fixed bodies, these are evolved based on absolute time, so cannot just fake it by reversing velocities and running forward
• DO let the integrators just run forrward
• do not evolve particles
• do not run triggers

Parameters

ge
physicsDt	Amount of time to be reversed (positive number!)

EvolveToTime()

void GravityState.EvolveToTime

(

double

newTime

)

Evolve all bodies to the new time (past or future). This will trigger a integration sequence when there is at least one body off rails and this may cause a burst of CPU activity if the time delta is large.

Generally called through the GE wrapper for game logic.

Parameters

newTime

GetMass()

double GravityState.GetMass

(

NBody

nbody

)

Return the internal physics engine mass.

Parameters

nbody

Returns

GetPhysicsPosition()

Vector3 GravityState.GetPhysicsPosition

(

NBody

nbody

)

Get the internal position used by the physics engine.

Parameters

nbody

Returns

GetPhysicsPositionDouble()

Vector3d GravityState.GetPhysicsPositionDouble

(

NBody

nbody

)

Get the internal position used by the physics engine.

Parameters

nbody

Returns

GetPhysicsTime()

double GravityState.GetPhysicsTime

(

)

Get the internal physics time for massive bodies.

Returns

physics time for massive body integrator

GetVelocityDouble()

void GravityState.GetVelocityDouble	(	NBody	nbody,
		ref double[]	vel
	)

Get the physics velocity for an NBody as a double[].

Parameters

nbody
vel

IsOnRails()

bool GravityState.IsOnRails

(

)

Are all bodies in the world state "on-rails"?

Returns

RemoveNBody()

void GravityState.RemoveNBody

(

NBody

nbody

)

Remove the body at index and shuffle up the rest. Ensure the integrator does the same to stay in alignment.

Parameters

index

SetAlgorithmAndForce()

void GravityState.SetAlgorithmAndForce	(	GravityEngine::Algorithm	algorithm,
		IForceDelegate	forceDelegate
	)

Set the integrator required for the chosen algorithm.

Parameters

algorithm

SetCenterOfMass()

void GravityState.SetCenterOfMass	(	GravityEngine	ge,
		Vector3d	pos,
		Vector3d	vel
	)

Set the CM to the specified postion and velocity.

Parameters

pos
vel

SetPosition3d()

void GravityState.SetPosition3d	(	NBody	nbody,
		Vector3d	pos
	)

Set the physics velocity from a double array.

Parameters

nbody
velocity

SetTime()

void GravityState.SetTime	(	double	newTime,
		bool	force
	)

See also

GravityEngine::SetPhysicalTime for restrictions.

Parameters

newTime

SetVelocityDouble()

void GravityState.SetVelocityDouble	(	NBody	nbody,
		ref double[]	velocity
	)

Set the physics velocity from a double array.

Parameters

nbody
velocity

UpdateInternalDouble()

void GravityState.UpdateInternalDouble	(	NBody	nbody,
		Vector3d	pos,
		Vector3d	velocity
	)

Internal use only from OrbitUniversal InitFromRVT Ensures cached state is current so can use info prior to the next Evolve call.

Parameters

nbody
pos
velocity

UpdateKeplerDepth()

void GravityState.UpdateKeplerDepth	(	NBody	nbody,
		OrbitUniversal	orbitU
	)

Recompute and update the kepler depth of a fixed body.

Parameters

nbody

UpdateOnRails()

void GravityState.UpdateOnRails

(

)

Check if all bodies are on rails.

Called after a RemoveBody in GE. Need to move to a single state RemoveBody() but wait until do masslessEngine refactor into integrator.

internal use only.

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

• C:/Users/musgr/Documents/Unity/gravityengine/Assets/GravityEngine/Scripts/Engine/GravityState.cs