Geant4 Workshop, CERN - 1 October 2002 Joseph Perl

Graphics Requirements for G4 TrajectoriesGraphics Requirements for G4 Trajectories(draft: hastily prepared for trajectories parallel session)(draft: hastily prepared for trajectories parallel session)

Geant4 Workshop, CERN - 1 October 2002 Geant4 Workshop, CERN - 1 October 2002 Joseph PerlJoseph Perl

1 October 20021 October 2002 Graphics Requirements for G4 Trajectories JoseGraphics Requirements for G4 Trajectories Joseph Perl, SLAC Computing Servicesph Perl, SLAC Computing Services

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Problem with Existing TrajectoriesProblem with Existing Trajectories

Graphics drivers have access to detailed information about Graphics drivers have access to detailed information about geometry since the sceneHandler has access to physical geometry since the sceneHandler has access to physical volume, etc. and can present this information to the end user volume, etc. and can present this information to the end user through labels on graphics objects or through picking.through labels on graphics objects or through picking.

Graphics drivers have no access to detailed information Graphics drivers have no access to detailed information about trajectories (or sensitive detector hits). The about trajectories (or sensitive detector hits). The sceneHandler only sees this data as graphics primitives (no sceneHandler only sees this data as graphics primitives (no pointer back to the trajectory).pointer back to the trajectory).

Graphics drivers have no access to auxiliary points. These Graphics drivers have no access to auxiliary points. These points are not persisted long enough for graphics to use points are not persisted long enough for graphics to use them, hence we can’t draw smooth trajectories.them, hence we can’t draw smooth trajectories.


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Auxiliary PointsAuxiliary Points On this topic, I only know what I’ve learned from John On this topic, I only know what I’ve learned from John

Allison. See his mail of 5 Sept 2002:Allison. See his mail of 5 Sept 2002:


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Effect of lack on information: Example T01Effect of lack on information: Example T01


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Picking on Detector Volumes Gives Detailed AttributesPicking on Detector Volumes Gives Detailed Attributes


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Picking on Trajectory Gives No DetailsPicking on Trajectory Gives No Details


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Picking on Trajectory if Graphics DriversPicking on Trajectory if Graphics Drivershad Better Access to Trajectory Informationhad Better Access to Trajectory Information


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Proposal for Better Graphics from TrajectoriesProposal for Better Graphics from Trajectories

• Give sceneHandler a DrawTrajectories method with pointer back to Trajectory

• Persist Auxiliary Points long enough for sceneHandler to use them to draw smooth trajectories

• Allow attachment of arbitrary attributes to Trajectories and Trajectory Points (and sensitive detector hits)

• A successful scheme for such arbitrary attributes has been used in HepRep for several years

The proposal is NOT for G4 to depend on HepRep The proposal is only for G4 to incorporate two small classes

that hold “HepRep-style” attributes. The HepRep attribute classes are just two simple classes

used in HepRep, they are not the entire HepRep design.


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The HepRep Attribute ClassesThe HepRep Attribute Classes

10/1/2002Joseph Perl HepRep218

*

*

*

**

*

*

1 1

1

1

1

1

1

HepRepInstance

HepRepTypeTree

HepRepInstanceTree

HepRepAttValue

HepRepType

HepRepAttDef

Linked by TypeName

ID: HepRepTreeID ID: HepRepTreeIDTypeTreeID:HRTreeIDInstanceTreeIDs:HRTreeID[]

Name: StringDesc: StringInfoURL: String

TypeName: String

X,Y,Z: Double

Name: StringDesc: StringCategory: StringExtra: String

AttDefName: StringValue: AnyShowLabel: Int

Linked by AttDefName

HepRepPoint

HepRepAction

Name:StringExpression:String

HepRep

Comments: String[]

HepRep: a Generic Interface Definition for HEP Event Display Representables

+getInstanceTreeTop(InstanceTreeName: String,InstanceTreeVersion: String):HepRepInstanceTree;

+getTypeTree(TypeTreeName: String,TypeTreeVersion: String):TypeTree;

+getInstances(InstanceTreeName: String,InstanceTreeVersion: String,TypeNames: String[]):HepRepInstanceTree;

+getInstancesAfterAction(InstanceTreeName: String,InstanceTreeVersion: String,TypeNames: String[],Actions:HepRepAction[],GetPoints: Boolean,GetDrawAtts: Boolean,GetNonDrawAtts: Boolean,InvertAtts: String[]):HepRepInstanceTree;

+getLayerOrder( ):String[];

+checkForException( ):String;

Comments: String[]HepRep HepRepTreeID

Name:StringVersion:String

Linked by TypeTreeID

1


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The HepRep Attribute ClassesThe HepRep Attribute Classes

HepRepAttValue

HepRepAttDef



In C++, the “any” is handled as a String that is In C++, the “any” is handled as a String that is interpreted according to an extra member of the interpreted according to an extra member of the AttDef called valueType.AttDef called valueType.

G4AttValue

G4AttDef

Name: StringDesc: StringCategory: StringExtra: StringValueType: String

AttDefName: StringValue: StringShowLabel: Int


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G4AttDef.h now in graphics_repsG4AttDef.h now in graphics_reps


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G4AttValue.h now in graphics_repsG4AttValue.h now in graphics_reps


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HepRep is Well Documented ElsewhereHepRep is Well Documented Elsewhere

For details on the exact use of HepRep Attributes, For details on the exact use of HepRep Attributes, see the HepRep Home Page at: see the HepRep Home Page at: http://heprep.freehep.orghttp://heprep.freehep.org

In particular, see the detailed HepRep2 writeup at:In particular, see the detailed HepRep2 writeup at:http://heprep.freehep.org/heprep2/Complete.ppthttp://heprep.freehep.org/heprep2/Complete.ppthttp://heprep.freehep.org/heprep2/Complete.pdfhttp://heprep.freehep.org/heprep2/Complete.pdf


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Any number of Attributes can be hungfrom a Type, Instance or Point.There are four Categories of Attributes:

•Draw Attributes (such as thicknessand color) can be modified in the clientthrough a draw attribute editor

•Physics Attributes (such as track momentum or hit error) can be used for visibility cuts (client side or server side)

•PickAction Attributes define special things to do when the user picks on theRepresentable (such as remove hit and refit track)

•Association Attributes define loose associations between Representables (such as track cluster matching)

Attribute Categories

To allow for the possible addition of new Categories without backwards compatibility problems, we keep Category as a general String, not an Enum.

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*1

1

1

HepRepInstance

HepRepType

Linked by TypeName TypeName: String

X,Y,Z: Double

HepRepPoint

**1 1

HepRepAttDef


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Name: StringDesc: StringInfoURL: String

HepRepAttValue




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Name Desc Extra Category ValueColor Color unused Draw BlueDrawAs DrawAs unused Draw EllipsoidPt Transverse Momentum GeV Physics 1.76PID Particle ID unused Physics PionSystem Detector System unused Physics Vertex DetectorRemove Remove Hit & Refit Track remove PickAction Track(5).Hit(8)Cluster Cluster Association ID Association 7Track Track Association TrkNum Association 5

HepRepAttDef



Attribute Examples

HepRepAttValue



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The Way ForwardThe Way Forward

• Give sceneHandler a DrawTrajectories method with pointer back to Trajectory

• Persist Auxiliary Points long enough for sceneHandler to use them to draw smooth trajectories

• Allow user to define arbitrary attributes in G4AttDef objects contained in a G4AttDefStore (map<string,G4AttDef> wrapped in a singelton) instantiated by the runManager.

• Allow attachment of G4AttValue attributes to Trajectories and Trajectory Points (and sensitive detector hits)

• G4AttValues do not contain a pointer to the relevant G4AttDef. The G4AttDef and G4AttValue association is done through a common string AttDefName. This simplifies many aspects of attribute use (AttValue user doesn’t need any way to get pointer, serialization is simpler, etc.).


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Extra SlideExtra Slidemore implementation details more implementation details

•We will have a singleton G4AttDefStore instantiated by the run manager.We will have a singleton G4AttDefStore instantiated by the run manager.

•Each trajectory (or trajectory point, hit, etc.) can call a method on this Each trajectory (or trajectory point, hit, etc.) can call a method on this G4AttDefStore to tell it to add an attDef, where first argument is name of G4AttDefStore to tell it to add an attDef, where first argument is name of type of objects that will have this attribute (trajectory, trajectory point, hit, type of objects that will have this attribute (trajectory, trajectory point, hit, etc.), and other arguments define the attDef.etc.), and other arguments define the attDef.The G4AttDefStore will just ignore this def if it has already been created for The G4AttDefStore will just ignore this def if it has already been created for some other trajectory (or trajectory point, etc.).some other trajectory (or trajectory point, etc.).

•The trajectory (or trajectory point, hit, etc.) will have a set of G4AttValues.The trajectory (or trajectory point, hit, etc.) will have a set of G4AttValues.The AttValues are linked to the AttDefs by att def name, rather than by a The AttValues are linked to the AttDefs by att def name, rather than by a pointer, thus the trajectory itself doesn't have to have any way to get a pointer, thus the trajectory itself doesn't have to have any way to get a pointer to the particular attDef.pointer to the particular attDef.We already rely on this weak form of association (association by name We already rely on this weak form of association (association by name rather than pointer) in our xml serialization of the HepRep.rather than pointer) in our xml serialization of the HepRep.

•At the end of the run, the run manager will destory the G4AttDefStore.At the end of the run, the run manager will destory the G4AttDefStore.

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Geant4 Workshop, CERN - 1 October 2002 Joseph Perl