Gravity Engine Core Central class for evolution using gravity and propagators. More...

Classes
struct	GEConfig

Public Types
enum	BodyType { MASSIVE_G , MASSLESS_G , FIXED , KEPLER_MASSIVE1 , KEPLER_MASSIVE2 , KEPLER_MASSIVE3 , KEPLER_MASSLESS , SGP4 , PKEPLER , EPHEMERIS , UNUSED }

enum	ReferenceFrame { INERTIAL , COROTATING_CR3BP }

Public Member Functions
	GECore (GECore ge, bool copyCallbacks=false)
	COPY CONSTRUCTOR Create a new GE as a clone of an existing GE.

	GECore (Integrators.Type integrator, GBUnits.Units defaultUnits, CR3BP.CR3BPSystemData cr3bpSystem, double stepsPerOrbit, double startTimeJD)
	Construct a GECore to perform evolution in the circular-restricted three body coordinate system (CR3BP). In this system the primary and secondary bodies are fixed and the equations of evolution model gravity and include terms to account for the rotating frame.

	GECore (Integrators.Type integrator, GBUnits.Units defaultUnits, double lengthScale, double massScale, double stepsPerOrbit, double startTimeJD=0)
	Construct a GECore to evolve bodies. The majority of the parameters relate to the scaling to be configured for numerical integration. Generally the information in/out is expressed in the defaultUnits (world units). The numerical integration is best when "typical values" of mass and length are of order 1. Internally physical parameters are scaled to obtain this.

ref GEPhysicsCore.GEBodies	BodiesGetAll ()

int	BodyAdd (double3 rWorld, double3 vWorld, double massWorld=0, bool isFixed=false)
	Adding Bodies.

int	BodyAddInOrbitWithCOE (Orbital.COE coeWorld, int centerId, GEPhysicsCore.Propagator prop, double massWorld=0.0, bool isPatched=false, double time_patch_start=0.0)
	Add a body in orbit relative to a center body using COE (classical orbital elements, a, eccentricy, inclination etc.)

int	BodyAddInOrbitWithRVRelative (double3 rWorld, double3 vWorld, int centerId, GEPhysicsCore.Propagator prop, double massWorld=0.0, bool isPatched=false, double time_patch_start=0.0)
	Add a body by specifying state relative to a second body. Typically this is used to place a body in orbit around a body when the specific R, V is known.

int	BodyAddInOrbitWithTLE (string tleData, int centerId, GEPhysicsCore.Propagator prop, bool isPatched=false, double time_patch_start=0.0)
	Add a body in orbit around Earth (only Earth!) using a two-line element data structure.

int	BodyAddWithEphemeris (EphemerisData ephemData, int cid, double m, bool isPatched=false, double time_patch_start=0.0)
	Add a body with a table of ephemeris data (a table of position and velocity at future times). Some websites (JPL) and third-party software tools can emit an ephemeris table.

bool	BodyRemove (int id)
	Remove a body from GECore.

BodyType	BodyTypeById (int id)
	Get the type of the body. Does not change at run time, so ok to just return it now.

Orbital.COE	COE (int bodyId, int centerId, bool usePropCOE=true)
	Get the classical orbital elements (COE) for the indicated body with respect to the center body.

void	ColliderAddToBody (int id, double radius, double bounceF, GEPhysicsCore.CollisionType collisionType, double mass)
	Add collision detection to a body. This results in the GEPhysicsCore performing comparisions to other bodies that habve collision detection enabled.

void	Complete ()
	Signal that jobs running must complete and wait for this to happen.

void	Dispose ()

double	Dt ()
	Numerical integration timestep value.

void	DtSet (double dt)
	Configure the internal timestep used in numerical integration.

string	DumpAll (string info="", bool worldScale=false)

void	EvolveNow (double tUntilWorld)

void	EvolveNowRecordOutput (double tUntilWorld, NativeArray< double > timePoints, NativeArray< int > bodies)
	Evolve the gravitational system in-line (may take more that one frame depending on the t_until) and record the state of the bodies described in bodies at the times in timePoints.

int	ExternalAccelerationAdd (int bodyId, ExternalAccel.ExtAccelType eaType, ExternalAccel.AccelType accelType, double3[] accelData=null)
	An external acceleration function can be added to a body. This acceleration may be a "self-force" (e.g. thrust from an ion drive) or a force from this bodyId to other bodies (e.g. the J2 force due to a non-spherical planet). This is specified by the eaType (SELF or ON_OTHER).

double3[]	ExternalAccelerationData (int extAccelId)
	Return a copy of the external acceleration params.

int	ExternalAccelerationDataOffset (int extAccelId)

void	ExternalAccelerationDataUpdate (int extAccelId, double3[] data)
	Update the external acceleration parameters for a specific external acceleration.

void	ExternalAccelerationRemove (int extAccelId)
	Remove the external acceleration.

GBUnits.GEScaler	GEScaler ()

double	GetParm (int index)
	Get information from the GE physics config.

GECore	GeTrajectory ()

bool	IsCompleted ()
	Poll to see if the jobs that were scheduled are complete.

bool	IsRunning ()
	Determine if GECore is currently running a physical loop.

void	ListenerAdd (GEListenerIF geListener)
	Add a listener.

void	ManeuverAdd (int id, GEManeuver m, double timeOffsetWorldTime=double.NaN)
	Add a maneuver to the list of pending maneuvers. If no timeOffset is given it is assumed the t_relative in the maneuver is to be added to the current time to establish the overall maneuver time.

List< int >	MassiveIndicesGet ()

double	MassWorld (int id)
	Return mass for a specified object.

double	MuWorld (int id)
	Return G * world mass for the body id given.

int	NumBodies ()
	Return the total number of bodies in GE (of all types)

int	NumRecordedBodies ()
	Number of bodies active in recording function.

bool	OnRails ()
	Determine if all bodies are using deterministic propagators aka all "On Rails". Conversly ensure no bodies are evolving using numerical integration of gravitational forces.

double	OrbitPeriodWorldTime ()
	Provide the time for one period of the reference (scale) orbit in world time units.

void	PatchAddToBody (int id, double3 r, double3 v, int centerId, GEPhysicsCore.Propagator prop, double time_start, double time_end=-1.0, double mass=0.0)
	Add a patch specified via R, V, T at the indicated start time.

void	PatchAddToBody (int id, Orbital.COE oe, int centerId, GEPhysicsCore.Propagator prop, double time_start, double time_end=-1.0, double mass=0.0)
	Add a patch specified via classical orbital elements (COE) at the indicated start time.

void	PhyLoopCompleteCallbackAdd (PhysLoopCompleteCallback cb, object arg=null)
	Add a callback to be invoked when GE physics loop completes running.

delegate void	PhysicsEventCallback (GECore ge, GEPhysicsCore.PhysEvent physEvent)

void	PhysicsEventListenerAdd (PhysicsEventCallback physEventCB)

void	PhysicsEventListenerRemove (PhysicsEventCallback physEventCB)

ref GEPhysicsCore.GEPhysicsJob	PhysicsJob ()
	Get a reference to the GEPhysicsJob.

delegate void	PhysLoopCompleteCallback (GECore ge, object arg=null)
	The most flexible way to ask GE to do things is via a callback when the physics loop is complete. This allows the scene to toggle between IMMEDIATE modes and job mode without code changes. When in immediate mode the callbacks are not stored and immediatly run.

void	PreCalcIntegration ()
	Call prior to beginning evolution in case integrator needs to set up internal info.

void	PropagateToTime (double tWorld, int id, ref GEBodyState state)
	Using the propagator for the ID propagate to the requested time and fill in the state struct with the R, V at that time.

GEPhysicsCore.Propagator	PropagatorTypeForId (int id)
	Return the propagator type for the specified id.

NativeArray< int >	RecordedBodies ()

NativeArray< GEBodyState >	RecordedOutputGEUnits ()
	Get a reference to the recorded output in GE units.

NativeArray< double >	RecordedTimesGEUnits ()

ReferenceFrame	RefFrame ()

bool	RelativeState (int bodyId, int centerId, ref GEBodyState bodyState, bool geUnits=false)
	Provide the state of a body relative to another body (typically the center body which the first body orbits.

void	RepositionAll (double3 r_offest)
	Apply a position and velocity transformation to all states.

double3	RWorldById (int id)
	Get the world position of a body of specified id.

void	Schedule (double tUntilWorld)
	Schedule the job to run until t_until. Do this in a way that the job can be continued with subsequent schedule calls.

void	ScheduleRecordOutput (double tUntilWorld, NativeArray< double > timePoints, NativeArray< int > bodies)
	Run GE evolution in "batch" mode and record the output at specified timePoints for the indicated bodies.

bool	StateById (int id, ref GEBodyState state, bool geUnits=false, bool maintainCoRo=false)
	Fill in a state using the id (unique to this GE). The state is at the current world time. Note that the current world time may slightly exceed the time that was requested in the preceeding Evolve() or Schedule() due to the finite step sixe in the numerical integration.

bool	StateByIdInterpolated (int id, ref GEBodyState state, double atTime, bool geUnits=false)
	Determine the state at a time that is slightly earlier than the current world time.

bool	StateSetById (int id, GEBodyState s, bool velocityOnly=false, bool relative=false, bool geUnits=false)

double	TimeGE ()
	Time in internal GECore units.

double	TimeJulianDays ()
	Time expressed as Julian days.

double	TimeWorld ()
	Time in world units (defaultUnits when GEC was created).

bool	TimeWorldSet (double worldTime)
	Set the world time.

void	TrajectoryRemove (int bodyId)
	Remove a trajectory from the trajectory recording. This will not require a trajectory reset so it can be done without too much fuss.

void	TrajectorySetup (double t_ahead, int numSteps, List< int > bodiesToRecord)
	Configure this GE to evolve forward by "timeAhead" recording positions at intervals of timeAhead/numSteps.

Public Attributes
Integrators.Type	integrator

Static Public Attributes
const double	DT_DEFAULT = 2.0 * math.PI / 500.0

const int	DT_PARAM = 0

const int	NUM_PARAMS = 9

const int	START_TIME_JD = 8

const int	T_END_JD = 3

const int	T_END_PARAM = 2

const int	T_PARAM = 1

const int	TRAJ_INDEX_PARAM = 4

const int	TRAJ_INTERVAL_PARAM = 7

const int	TRAJ_NUM_UPDATED_PARAM = 6

const int	TRAJ_NUMSTEPS_PARM = 5

Detailed Description

Gravity Engine Core Central class for evolution using gravity and propagators.

Handles:

evolution directly or as a job
management of physics data structures for bodies, maneuvers, patches etc.
handles body additions with a variety of initial conditions (RV, COE, ephemeris, TLE etc.)
the physics evolution is handed to
See also
GEPhysicsCore
This class can be used directly or
See also
GSController will instantiate a instance.
Since execution may be via the Unity job system a large part of what GECore does is to arrange data into arrays suitable for use in the job system. This aids in memory locality and speed. Hence there are often parallel data stores for info in GECore as lists and then an array version of the info for GEPhysicsCore.

Constructor & Destructor Documentation

◆ GECore() [1/3]

GravityEngine2.GECore.GECore	(	Integrators::Type	integrator,
		GBUnits::Units	defaultUnits,
		double	lengthScale,
		double	massScale,
		double	stepsPerOrbit,
		double	startTimeJD = 0 )

Construct a GECore to evolve bodies. The majority of the parameters relate to the scaling to be configured for numerical integration. Generally the information in/out is expressed in the defaultUnits (world units). The numerical integration is best when "typical values" of mass and length are of order 1. Internally physical parameters are scaled to obtain this.

Parameters

integrator	specify numerical inegration scheme
defaultUnits
lengthScale	length in world units that will be 1 physics unit
massScale	mass in world units that will be 1 mass unit
stepsPerOrbit	suggested number of time steps per circular orbit of radius lengthScale
startTimeJD	start time in Julian date format (only needed when satellite info in TLEs)

◆ GECore() [2/3]

GravityEngine2.GECore.GECore	(	Integrators::Type	integrator,
		GBUnits::Units	defaultUnits,
		CR3BP::CR3BPSystemData	cr3bpSystem,
		double	stepsPerOrbit,
		double	startTimeJD )

Construct a GECore to perform evolution in the circular-restricted three body coordinate system (CR3BP). In this system the primary and secondary bodies are fixed and the equations of evolution model gravity and include terms to account for the rotating frame.

This constructor explcitly adds the primary and secondary bodies based on the information in the cr3bpSystem parameter.

Parameters

integrator
defaultUnits
cr3bpSystem
stepsPerOrbit
startTimeJD

Exceptions

NotSupportedException

◆ GECore() [3/3]

GravityEngine2.GECore.GECore	(	GECore	ge,
		bool	copyCallbacks = false )

COPY CONSTRUCTOR Create a new GE as a clone of an existing GE.

the clone will have the same id mapping for bodies and internal structure
NotRunningCallbacks may optionally NOT be copied (since likely want to attach new ones)

Parameters

ge
copyCallbacks

Member Function Documentation

◆ BodiesGetAll()

ref GEPhysicsCore.GEBodies GravityEngine2.GECore.BodiesGetAll ( )

Returns

◆ BodyAdd()

int GravityEngine2.GECore.BodyAdd	(	double3	rWorld,
		double3	vWorld,
		double	massWorld = 0,
		bool	isFixed = false )

Adding Bodies.

Add a body with absolute world R, V, mass state information to GE with world information expressed in the defaultUnits specified in the GECore constructor.

There is no general propagator choice in this case because all the propagators are relative to some center body. To add with a propagtor use one of the BodyAddInOrbitWithRVRelative or BodyAddInOrbitWithCOE methods. are relative to some center body. To add with a propagator use one of

See also: BodyAddInOrbitWithRVRelative; BodyAddInOrbitWithCOE; BodyAddInOrbitWithTLE

Parameters

rWorld	position in World default units
vWorld	velocity in World default units
massWorld	world mass (may be zero)
isFixed	(optional) body is fixed and will not be moved by GE

Returns

◆ BodyAddInOrbitWithCOE()

int GravityEngine2.GECore.BodyAddInOrbitWithCOE	(	Orbital::COE	coeWorld,
		int	centerId,
		GEPhysicsCore::Propagator	prop,
		double	massWorld = 0::0,
		bool	isPatched = false,
		double	time_patch_start = 0::0 )

Add a body in orbit relative to a center body using COE (classical orbital elements, a, eccentricy, inclination etc.)

For patching information see comments in BodyAddInOrbitWithRVRelative

Parameters

coeWorld	orbit elements in default units
centerId	id of center body of orbit
prop	propagator
massWorld	mass of body to add
isPatched	updates to this body as patches
time_patch_start	time patches start

Returns

◆ BodyAddInOrbitWithRVRelative()

int GravityEngine2.GECore.BodyAddInOrbitWithRVRelative	(	double3	rWorld,
		double3	vWorld,
		int	centerId,
		GEPhysicsCore::Propagator	prop,
		double	massWorld = 0::0,
		bool	isPatched = false,
		double	time_patch_start = 0::0 )

Add a body by specifying state relative to a second body. Typically this is used to place a body in orbit around a body when the specific R, V is known.

To put a body in orbit using orbit parameters BodyAddInOrbitWithCOE

Patching: Bodies that have deterministic (i.e. no numerical integration) propagators are candidates to be "patched". A patched body records subsequent changes in state (r, v) by appending a propagator segment to the body. The patch has an associated start and end time and the evolution code uses the patch corresponding to the current time.

Patching is typically used to either:

handle a maneuver sequence in a way that allows time to be jumped forward or backward
implement a sequence of orbital propagators (aka conics) to model movement from one gravity system to another where only one system at a time exerts a gravitational force.

Parameters

rWorld	relative position in default units
vWorld	relative velocity in default units
centerId	body id of center body
prop	propagator type
massWorld	mass of object to add
isPatched	subsequent changes should be added as patches
time_patch_start	time of first patch

Returns

◆ BodyAddInOrbitWithTLE()

int GravityEngine2.GECore.BodyAddInOrbitWithTLE	(	string	tleData,
		int	centerId,
		GEPhysicsCore::Propagator	prop,
		bool	isPatched = false,
		double	time_patch_start = 0::0 )

Add a body in orbit around Earth (only Earth!) using a two-line element data structure.

Earth satellite information is often expressed in a two-line forms (e.g. celestrak.com) which harkens back to two 80 column punch cards (some API choices are "sticky"!).

Use of this method requires that the center body have the mass of the Earth. It also requires that the start time of the GECore in Julian days has been configured. Satellite data provides the orbit information at a specific date/time and this time must be earlier than the start time of GECore.

For patching information see comments in BodyAddInOrbitWithRVRelative

Parameters

tleData	string representing the two line element info
centerId	id of center body
prop	propagator
isPatched	handle updates to state as patches
time_patch_start

Returns

◆ BodyAddWithEphemeris()

int GravityEngine2.GECore.BodyAddWithEphemeris	(	EphemerisData	ephemData,
		int	cid,
		double	m,
		bool	isPatched = false,
		double	time_patch_start = 0::0 )

Add a body with a table of ephemeris data (a table of position and velocity at future times). Some websites (JPL) and third-party software tools can emit an ephemeris table.

Ephemeris data is wrapped in a class.

For patching information see comments in BodyAddInOrbitWithRVRelative

Parameters

ephemData	ephemeris data
cid	center body
m	mass of body
isPatched	handle updates as patches
time_patch_start

Returns

◆ BodyRemove()

bool GravityEngine2.GECore.BodyRemove ( int id )

Remove a body from GECore.

Parameters

id

◆ BodyTypeById()

BodyType GravityEngine2.GECore.BodyTypeById ( int id )

Get the type of the body. Does not change at run time, so ok to just return it now.

Parameters

id

Returns

◆ COE()

Orbital.COE GravityEngine2.GECore.COE	(	int	bodyId,
		int	centerId,
		bool	usePropCOE = true )

Get the classical orbital elements (COE) for the indicated body with respect to the center body.

The most common way to do this is to take the R, V state of the body and use an algorithm (RVtoCOE) to determine the COE elements. This algorithm imposes a choice of when an orbit is to be considered flat or circular.

A flat orbit (i=0) has it's OmegaU/RAAN set to 0. A circular orbit has it's argp set to zero (this is the reference point for the phase, nu).

Of course the zero detect is not exactly zero, so there will be some threshold (usually E-6) where e.g. an orbit can transition from flat to non-flat. When this happens the argp and phase may have a discontinuity (athough their sum will remain constant).

Parameters

bodyId
centerId
usePropCOE	If propagator has internal COE, use that instead of recomputing from R, V

Returns

◆ ColliderAddToBody()

void GravityEngine2.GECore.ColliderAddToBody	(	int	id,
		double	radius,
		double	bounceF,
		GEPhysicsCore::CollisionType	collisionType,
		double	mass )

Add collision detection to a body. This results in the GEPhysicsCore performing comparisions to other bodies that habve collision detection enabled.

Collision detection is performed by checking if the separation of the bodies is less than the sum of their radii (ie. as if there were spherical colliders).

This collision detection is internal to GECore and is not related to the Unity physics collision detection system.

The mass provided to the collision system is not necessarily the same as the gravitational mass. For example it makes sense to treat a satellite as having zero gravitational mass (so force of satellite on Earth is not computed) but for the purpose of a collision a mass e.g. 2000 kg is appropriate.

Parameters

id	body id
radius	spherical size of this body in default World units
bounceF	bounce factor for elastic collisions
collisionType	interaction type (absorb/bounce)
mass	inertial mass

◆ Complete()

void GravityEngine2.GECore.Complete ( )

Signal that jobs running must complete and wait for this to happen.

If a trajectory job is also being used, this will complete also.

◆ Dt()

double GravityEngine2.GECore.Dt ( )

Numerical integration timestep value.

Returns

◆ DtSet()

void GravityEngine2.GECore.DtSet ( double dt )

Configure the internal timestep used in numerical integration.

Parameters

dt

◆ DumpAll()

string GravityEngine2.GECore.DumpAll	(	string	info = "",
		bool	worldScale = false )

Parameters

info
worldScale

Returns

◆ EvolveNow()

void GravityEngine2.GECore.EvolveNow ( double tUntilWorld )

Parameters

tUntilWorld

◆ EvolveNowRecordOutput()

void GravityEngine2.GECore.EvolveNowRecordOutput	(	double	tUntilWorld,
		NativeArray< double >	timePoints,
		NativeArray< int >	bodies )

Evolve the gravitational system in-line (may take more that one frame depending on the t_until) and record the state of the bodies described in bodies at the times in timePoints.

The result is placed in a large linear NativeArray indexed as: timePointNum * numBodies +

Parameters

t_until
timePoints
bodies

◆ ExternalAccelerationAdd()

int GravityEngine2.GECore.ExternalAccelerationAdd	(	int	bodyId,
		ExternalAccel::ExtAccelType	eaType,
		ExternalAccel::AccelType	accelType,
		double3[]	accelData = null )

An external acceleration function can be added to a body. This acceleration may be a "self-force" (e.g. thrust from an ion drive) or a force from this bodyId to other bodies (e.g. the J2 force due to a non-spherical planet). This is specified by the eaType (SELF or ON_OTHER).

The return value is an index to the external acceleration. Updates to the acceleration parameters require a reference to the external acceleration. (A given body ID may have more that one external acceleration e.g. rocket engine and atmospheric drag).

The application of the acceleration takes place in the depths of GEPhysicsCore numerical integration and this may use the Job system: Consequently

any parameter information must be presented as a block of double3[].
function pointers are not permitted [*]. Any user defined forces will require an extension in
See also
ExtAccelFactory
Each function can take a block of double3[] as parameters and scratch memory.

[*] technically an unsafe function pointer can be used, but the Asset Store does not permit assets to declare unsafe code.

Parameters

bodyId	identity of body to compute external acceleration
eaType	type of force (self/on-other)
accelType	enumerated type to slect force
accelData	parameters for force calculation

Returns: id for the acceleration

◆ ExternalAccelerationData()

double3[] GravityEngine2.GECore.ExternalAccelerationData ( int extAccelId )

Return a copy of the external acceleration params.

Parameters

extAccelId the id of the external acceleration (NOT bodyId!)

Returns

◆ ExternalAccelerationDataUpdate()

void GravityEngine2.GECore.ExternalAccelerationDataUpdate	(	int	extAccelId,
		double3[]	data )

Update the external acceleration parameters for a specific external acceleration.

Parameters

extAccelId
data

◆ ExternalAccelerationRemove()

void GravityEngine2.GECore.ExternalAccelerationRemove ( int extAccelId )

Remove the external acceleration.

Parameters

extAccelId

◆ GEScaler()

GBUnits.GEScaler GravityEngine2.GECore.GEScaler ( )

Get the GEScalar. Used when code needs to determine conversions from physics space (GEC internal) to world units.

Returns: GEScalar

◆ GetParm()

double GravityEngine2.GECore.GetParm ( int index )

Get information from the GE physics config.

Parameters

index

Returns

◆ IsCompleted()

bool GravityEngine2.GECore.IsCompleted ( )

Poll to see if the jobs that were scheduled are complete.

Returns

◆ IsRunning()

bool GravityEngine2.GECore.IsRunning ( )

Determine if GECore is currently running a physical loop.

Returns

◆ ListenerAdd()

void GravityEngine2.GECore.ListenerAdd ( GEListenerIF geListener )

Add a listener.

Currently used to get a callback when a body is removed due to a collision.

Parameters

geListener

◆ ManeuverAdd()

void GravityEngine2.GECore.ManeuverAdd	(	int	id,
		GEManeuver	m,
		double	timeOffsetWorldTime = double::NaN )

Add a maneuver to the list of pending maneuvers. If no timeOffset is given it is assumed the t_relative in the maneuver is to be added to the current time to establish the overall maneuver time.

If an explicit timeOffset is provided, use it.

If the body the maneuver is being applied to is patched, and the maneuver has isPatched then instead of adding a maneuver we can add a patch. It is assumed that maneuvers for a given id are added in increasing time order. (Note: GEPhysicsJob cannot easily create a patch "on the fly" since it would need to dynamically change it's data structures and let GE know. This could be solved but defer for now).

Note that the GEManeuver instances are kept in GE but must be converted into a GEManeuverStruct for the IJob (it cannot handle classes).

Life Cycle: Maneuvers are added to pendingManeuvers. GECore then copies this list of manuvers into a NativeList<GEManeuverStruct>. Once a maneuver has been executed by the physics core it generates a PhysEvent. PhysicsLoopComplete() examines those maneuvers that have been executed and runs their callbacks (if present). These are then removed from the masterManeuverList and the pending

Note that this means the callbacks will occur when Evolve() loop completes and not when the maneuver occurs. As a result the current GECore state will not correspond to the state at the time of the maneuver. The exact time, position and before/after velocity of the maneuver is contained in the PhysEvent that reports the maneuver was completed.

Parameters

id	id of body
m	maneuver to be added
timeOffsetWorldTime	(optional) specific offset for maneuver. By default current world time is used.

◆ MassiveIndicesGet()

List< int > GravityEngine2.GECore.MassiveIndicesGet ( )

Returns

◆ MassWorld()

double GravityEngine2.GECore.MassWorld ( int id )

Return mass for a specified object.

Parameters

id

Returns

◆ MuWorld()

double GravityEngine2.GECore.MuWorld ( int id )

Return G * world mass for the body id given.

Parameters

id

Returns: mass

◆ NumBodies()

int GravityEngine2.GECore.NumBodies ( )

Return the total number of bodies in GE (of all types)

Returns

◆ NumRecordedBodies()

int GravityEngine2.GECore.NumRecordedBodies ( )

Number of bodies active in recording function.

Returns

◆ OnRails()

bool GravityEngine2.GECore.OnRails ( )

Determine if all bodies are using deterministic propagators aka all "On Rails". Conversly ensure no bodies are evolving using numerical integration of gravitational forces.

Returns

◆ OrbitPeriodWorldTime()

double GravityEngine2.GECore.OrbitPeriodWorldTime ( )

Provide the time for one period of the reference (scale) orbit in world time units.

Returns

◆ PatchAddToBody() [1/2]

void GravityEngine2.GECore.PatchAddToBody	(	int	id,
		double3	r,
		double3	v,
		int	centerId,
		GEPhysicsCore::Propagator	prop,
		double	time_start,
		double	time_end = -1::0,
		double	mass = 0::0 )

Add a patch specified via R, V, T at the indicated start time.

This can only be performed on a body for which patch mode is enabled.

Parameters

id
r
v
centerId
prop
time_start
time_end
mass

◆ PatchAddToBody() [2/2]

void GravityEngine2.GECore.PatchAddToBody	(	int	id,
		Orbital::COE	oe,
		int	centerId,
		GEPhysicsCore::Propagator	prop,
		double	time_start,
		double	time_end = -1::0,
		double	mass = 0::0 )

Add a patch specified via classical orbital elements (COE) at the indicated start time.

This can only be performed on a body for which patch mode is enabled.

Wrapper on the RV AddPatch.

Parameters

id
oe
centerId
prop
time_start
time_end
mass

◆ PhyLoopCompleteCallbackAdd()

void GravityEngine2.GECore.PhyLoopCompleteCallbackAdd	(	PhysLoopCompleteCallback	cb,
		object	arg = null )

Add a callback to be invoked when GE physics loop completes running.

This is used when GE is using an IJob on another thread to ensure that changes to state, adding, removing etc are not done while GE is using the physics data.

Physics data from a coherent snapshot can be retreived when the physics loop is running. It cannot be set. This makes code to e.g. compare distance between bodies to run in Update() methods without adding callbacks.

If GE is in immediate mode this code will simply call the cb immediatly. Changes can always be wrapped this way and the control code does not need to care if GE is running physics or not.

Parameters

cb

◆ PhysicsEventCallback()

delegate void GravityEngine2.GECore.PhysicsEventCallback	(	GECore	ge,
		GEPhysicsCore.PhysEvent	physEvent )

Parameters

ge
physEvent

◆ PhysicsEventListenerAdd()

void GravityEngine2.GECore.PhysicsEventListenerAdd ( PhysicsEventCallback physEventCB )

Parameters

physEventCB

◆ PhysicsEventListenerRemove()

void GravityEngine2.GECore.PhysicsEventListenerRemove ( PhysicsEventCallback physEventCB )

Parameters

physEventCB

◆ PhysicsJob()

ref GEPhysicsCore.GEPhysicsJob GravityEngine2.GECore.PhysicsJob ( )

Get a reference to the GEPhysicsJob.

Used by GSController for particle update.

User use at your own risk.

Returns

◆ PhysLoopCompleteCallback()

delegate void GravityEngine2.GECore.PhysLoopCompleteCallback	(	GECore	ge,
		object	arg = null )

The most flexible way to ask GE to do things is via a callback when the physics loop is complete. This allows the scene to toggle between IMMEDIATE modes and job mode without code changes. When in immediate mode the callbacks are not stored and immediatly run.

This does result in unnecessary indirection when using only IMMEDIATE mode, so it can be skipped if IMMEDIATE mode will not be changed during development.

Parameters

ge
arg

◆ PropagateToTime()

void GravityEngine2.GECore.PropagateToTime	(	double	tWorld,
		int	id,
		ref GEBodyState	state )

Using the propagator for the ID propagate to the requested time and fill in the state struct with the R, V at that time.

If the propagator does not support this, set the time to a negative number.

This only does relative propagation.

Parameters

t	world time to propagate to
id	id of body to propagate
state	struct to hold state info (ref)

◆ PropagatorTypeForId()

GEPhysicsCore.Propagator GravityEngine2.GECore.PropagatorTypeForId ( int id )

Return the propagator type for the specified id.

Parameters

id

Returns

◆ RecordedBodies()

NativeArray< int > GravityEngine2.GECore.RecordedBodies ( )

Returns

◆ RecordedOutputGEUnits()

NativeArray< GEBodyState > GravityEngine2.GECore.RecordedOutputGEUnits ( )

Get a reference to the recorded output in GE units.

The output is arranged in "body major" sequence. At timePoint[0] entries 0..numBodies will hold state for each body at time zero. At tp[1] the info is at numBodies..2*numBodies-1 etc.

In the case of trajectory data the array is written as a circular buffer and the last written entry can be determined by TrajectoryStatus()

Returns

◆ RecordedTimesGEUnits()

NativeArray< double > GravityEngine2.GECore.RecordedTimesGEUnits ( )

Returns

◆ RelativeState()

bool GravityEngine2.GECore.RelativeState	(	int	bodyId,
		int	centerId,
		ref GEBodyState	bodyState,
		bool	geUnits = false )

Provide the state of a body relative to another body (typically the center body which the first body orbits.

Parameters

bodyId	id for which state info is requested
centerId	id for which state is relative to
bodyState	struct to hold the state information (ref)
geUnits	return value in internal GE units (by default will be in world units)

Returns

◆ RepositionAll()

void GravityEngine2.GECore.RepositionAll ( double3 r_offest )

Apply a position and velocity transformation to all states.

Useful to move entire system to e.g. center of mass position and velocity.

Parameters

r_offest

◆ RWorldById()

double3 GravityEngine2.GECore.RWorldById ( int id )

Get the world position of a body of specified id.

Parameters

id

Returns

◆ Schedule()

void GravityEngine2.GECore.Schedule ( double tUntilWorld )

Schedule the job to run until t_until. Do this in a way that the job can be continued with subsequent schedule calls.

Parameters

tUntilWorld end time of gravity evolution

◆ ScheduleRecordOutput()

void GravityEngine2.GECore.ScheduleRecordOutput	(	double	tUntilWorld,
		NativeArray< double >	timePoints,
		NativeArray< int >	bodies )

Run GE evolution in "batch" mode and record the output at specified timePoints for the indicated bodies.

Parameters

tUntilWorld
timePoints
bodies

◆ StateById()

bool GravityEngine2.GECore.StateById	(	int	id,
		ref GEBodyState	state,
		bool	geUnits = false,
		bool	maintainCoRo = false )

Fill in a state using the id (unique to this GE). The state is at the current world time. Note that the current world time may slightly exceed the time that was requested in the preceeding Evolve() or Schedule() due to the finite step sixe in the numerical integration.

Return value is in default world units unless geUnits are explicitly requested.

Parameters

id	id of body
state	struct to hold state info (ref)
geUnits	return value in internal GE units (by default will be in world units)

Returns

◆ StateByIdInterpolated()

bool GravityEngine2.GECore.StateByIdInterpolated	(	int	id,
		ref GEBodyState	state,
		double	atTime,
		bool	geUnits = false )

Determine the state at a time that is slightly earlier than the current world time.

This can be used when a high precision state is required. For example:

GECore is asked to evolve to t=10.1
due to internal dt step it evolves to t=10.13
the state at exactly t=10.1 is of interest In this case asking for the state at time 10.1 will result in an linear interpolation of r and v by the delta.

Parameters

id	body to retrieve state for
state	struct to hold state information (ref)
atTime	specific world time to intepolate state to (less than current world time)
geUnits	return value in internal GE units (by default will be in world units)

Returns

◆ StateSetById()

bool GravityEngine2.GECore.StateSetById	(	int	id,
		GEBodyState	s,
		bool	velocityOnly = false,
		bool	relative = false,
		bool	geUnits = false )

Parameters

id
s
velocityOnly
relative
geUnits

Returns

◆ TimeGE()

double GravityEngine2.GECore.TimeGE ( )

Time in internal GECore units.

When GEC is configured for ideal scaling (center mass = 1, orbit radius = 1) then the scaling will result in an orbit period of 2 Pi (6.28-ish).

Returns

◆ TimeJulianDays()

double GravityEngine2.GECore.TimeJulianDays ( )

Time expressed as Julian days.

Returns

◆ TimeWorld()

double GravityEngine2.GECore.TimeWorld ( )

Time in world units (defaultUnits when GEC was created).

When in Job mode this function cannot be called when the job is running since time is evolving in the job system. In that case use this function within code added to a physics loop complete callback.

Returns

◆ TimeWorldSet()

bool GravityEngine2.GECore.TimeWorldSet ( double worldTime )

Set the world time.

This is only permitted if all bodies have determinsitic propagators i.e. everything is "on-rails". In such cases the time can be jumped to the future or the past.

Note:

any consumed maneuvers will not be undone. This is not a true rewind.
if a true rewind is needed for some rails objects, consider enabling patches for those bodies

Parameters

worldTime

Returns

◆ TrajectoryRemove()

void GravityEngine2.GECore.TrajectoryRemove ( int bodyId )

Remove a trajectory from the trajectory recording. This will not require a trajectory reset so it can be done without too much fuss.

Parameters

bodyId

◆ TrajectorySetup()

void GravityEngine2.GECore.TrajectorySetup	(	double	t_ahead,
		int	numSteps,
		List< int >	bodiesToRecord )

Configure this GE to evolve forward by "timeAhead" recording positions at intervals of timeAhead/numSteps.

This is also used when a new body is added: build a new list of bodiesToRecord and run a new setup. [A trajectory reset is needed and more memory needs to be allocated for the circular buffer so there is simple way to 'just' do an add.]

Typical usage: 1) Clone an existing GE (into trajClone, say) and set the clone with ConfigTrajectory 2) Register the trajectory clone with the intial GE so that if there are changes (body add/del etc.) the clone can recompute it's trajectories 3) Have the display/evolve code run the evolution for trajClone the same way it does for GE 4) Display code then retrieves the update position info from trajClone and displays

Parameters

t_ahead	time into future to determine trajectoories
numSteps	number of intermediate values to asses
bodiesToRecord	indices of bodies to gather trajectory information for

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

ge2/GE2/Assets/GravityEngine2/Runtime/Core/GECore.cs

Classes

Public Types

Public Member Functions

Public Attributes

Static Public Attributes

Detailed Description

Constructor & Destructor Documentation

◆ GECore() [1/3]

◆ GECore() [2/3]

◆ GECore() [3/3]

Member Function Documentation

◆ BodiesGetAll()

◆ BodyAdd()

◆ BodyAddInOrbitWithCOE()

◆ BodyAddInOrbitWithRVRelative()

◆ BodyAddInOrbitWithTLE()

◆ BodyAddWithEphemeris()

◆ BodyRemove()

◆ BodyTypeById()

◆ COE()

◆ ColliderAddToBody()

◆ Complete()

◆ Dt()

◆ DtSet()

◆ DumpAll()

◆ EvolveNow()

◆ EvolveNowRecordOutput()

◆ ExternalAccelerationAdd()

◆ ExternalAccelerationData()

◆ ExternalAccelerationDataUpdate()

◆ ExternalAccelerationRemove()

◆ GEScaler()

◆ GetParm()

◆ IsCompleted()

◆ IsRunning()

◆ ListenerAdd()

◆ ManeuverAdd()

◆ MassiveIndicesGet()

◆ MassWorld()

◆ MuWorld()

◆ NumBodies()

◆ NumRecordedBodies()

◆ OnRails()

◆ OrbitPeriodWorldTime()

◆ PatchAddToBody() [1/2]

◆ PatchAddToBody() [2/2]

◆ PhyLoopCompleteCallbackAdd()

◆ PhysicsEventCallback()

◆ PhysicsEventListenerAdd()

◆ PhysicsEventListenerRemove()

◆ PhysicsJob()

◆ PhysLoopCompleteCallback()

◆ PropagateToTime()

◆ PropagatorTypeForId()

◆ RecordedBodies()

◆ RecordedOutputGEUnits()

◆ RecordedTimesGEUnits()

◆ RelativeState()

◆ RepositionAll()

◆ RWorldById()

◆ Schedule()

◆ ScheduleRecordOutput()

◆ StateById()

◆ StateByIdInterpolated()

◆ StateSetById()

◆ TimeGE()

◆ TimeJulianDays()

◆ TimeWorld()

◆ TimeWorldSet()

◆ TrajectoryRemove()

◆ TrajectorySetup()