Alverson, G

Barrand, Guy

Boudreau, Joe

Böhnlein, A

Fan Xioa Ling

Gaponenko, Iana A

Kallenbach, Jeff

Kubarovsky, Andrey V

Lebrun, P

Taylor, Lucas

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Status of the HEPVis Class LibraryGeorge Alverson (Northeastern Univ.), Guy Barrand (LAL/Orsay), Amber Boehnlein (FNAL), JoeBoudreau (Univ. Of Pittsburgh), Xioaling Fan (FNAL), Iana Gaponenko (CERN), Jeff Kallenbach (FNAL),Andrey Kubarovsky (FNAL), Paul Lebrun (FNAL), Lucas Taylor (Northeastern Univ.)Abstract:Since 1994 a group of High Energy Physicists and Computer Scientists have been collaborating on HEPVis,a library of 2-D and 3-D shapes for detector visualization and HEP analysis.  Based on the Open Inventor (1)toolkit, HEPVis has grown into an international collaboration since its inception in 1994.  This paperdescribes the library, its history, and its future.  Images from HEP applications that use the library are alsoincluded.1. IntroductionThe HEPVis class library was created and is maintained with the following goals in mind:• Identification of common elements of interactive detector and event visualization and analysis systems,to avoid duplication of effort• Provision of an object-oriented class library with the following properties:• Generic graphics classes for detector and event objects.• Components for the construction of portable graphical user interfaces.  This includes viewers withintuitive, HEP-specific controls and easily extensible menus.• Consistency with HEP software strategies.  We intend the library to be used as part of thecomputing suite of LHC, FNAL Run II, GEANT4, and other near-term HEP projects.• Based on mainstream technologies.  OpenGL 2 and OpenInventor are proven, widely usedtechnologies that integrate easily into different applications.• Participation in a forum, approximately every 18 months, for sharing progress. HEPVis workshopshave been held at FNAL in 1995, CERN in 1996, and at SLAC in 1998.2. History• 1994 - The HEPVis library originated by Joe Boudreau.  Concept for the entire project, and some basicshapes.• 1996 – Collaborators were solicited at the HEPVis96 Workshop at CERN.   Fermilab committed towriting an Open Inventor graphics subsystem for the Geant4 collaboration.  As part of this effort, OpenInventor subclasses of the Geant4 shapes were developed, as well as complete viewers that make use ofthe library shapes.• 1997 - Joe Boudreau and Matt Schell wrote the CDF Run II tracking program, which makes use of thelibrary’s Event Viewer.  This application was used in the first Virtual Reality demonstration at FNAL.The L3, and CMS experiments began using the library.  Guy Barrand contributed additional classes andoptimization.• 1998 – The library went into code management.  CDF and D0 began experimenting3. HEPVis Library Contents3.1 Basic ShapesThe basic shape classes in the library are SoG4Box, SoG4Tubs, SoG4Cons, SoHelicalTrack, SoEllipsoid,SoEllipticalPrism, SoG4Trap, and SoG4Trd.  These are subclasses of Open Inventor classes, with memberdata corresponding to various physical properties.  In the case of SoG4*, they are also subclasses of thecorresponding Geant4 shapes.3.2 Complex Shapes/Node KitsThe next level of HEPVis shapes are the complex shapes and node kits.  This group includes SoSiStrips,SoSiStripDetKit, SoDblStripDetKit, SoStereoStripDetKit, and SoDetectorTreeKit.  They are subclasses ofthe Open Inventor nodes, and are used to construct the detector in a hierarchical form.  The library providesthe capability to edit the detector components interactively.  By clicking with the mouse, the user can editthe material property or actually “move” the component out of the way to expose the underlyingcomponents.Figure 1 – HEPVis primitives – basic shapes, SoSiStrips, SoDetectorTreeKitFigure 1 shows a number of the basic shapes and features of the HEPVis library.  In the upper left,SoHelicalTrack and SpVtxReconTrack are used to represent tracks in two different ways.  SoEllipsoid isused to display a computed vertex.  In the upper right, SoSiStripDetKit and SoStereoStripDetKit are used toshow silicon strips on a wafer.  Note the stereo strips, and how the pulse height is shown using the height ofthe strip.  In the bottom view, SoDetectorTreeKit is used to show the layers of a silicon detector.  Usingmouse clicks, the user of the program can “peel off” layers of the detector to view, at different points, thebarrel exteriors, the wedges, or the individual silicon wafers.  Note how in all views color is used todifferentiate between the various components.3.3 Widgets & Add-onsIn addition to basic shapes and primitives, HEPVis also contains X widgets and annotators.  SoArrow andSbAxis can be used to add 3D arrows and axes to the Open Inventor scene, respectively.  TheSmPushButton class adds an X pushbutton and the corresponding callback. SoPlotter is a new class thatprovides the capability to add an histogram to the Open Inventor scene.  The key here is the fact that thenew nodes and their corresponding data are actually part of the entire scene being visualized.3.4 ViewersHEPVis also comes with two viewer classes, SoXtHepViewer and SoXtHepEventViewer.  These viewersare extensions of the Open Inventor class SoXtFullViewer, and as such provide full 3D control, materialeditors, and other value-added features.  In addition, the HEPVis viewers provide the following features:• Intuitive control of scene & data.  Conventional mouse clicks are used for selection, rotation, etc.• C++ provides extensibility.  For example, the CDF tracking program is a subclass ofSoXtHepEventViewer, which in turn is a subclass of SoXtHepViewer.• The GUI can be extended by adding to the default menu bar or by creating new panels.• Complete management of selection lists• Node Kits provide scene reduction & geometry hierarchy4.0 HEPVis in use4.1 CDF RunII TrackingFigure 2 – CDF RunII Tracking using SoXtHepEventViewerFigure 2 shows features of SoXtHepEventViewer as used in the CDF RunII tracking.  The intuitive menubar appears, and properties of the selected particle appear in the message box.  Color and linestyle are usedto distinguish different particles.  The ISL is transparent to expose the SVX.  One SVX wedge has beenremoved to expose individual wafers.Figure 3 – Multiple views in the SoXtHepEventViewerFigure 3 shows different features of SoXtHepEventViewer.  The left side shows a computed vertex alongwith the tracks from which it was computed.  The multiple views remain in synch.  On the right side is ashot of the full viewer.  The intuitive menu bar and message box appear.  Color and linestyle are used todistinguish different particles, and zoomed and panned views orient the user.4.2 L3/CMS 3Figure 4 – An event in the L3 detector displayed using a prototype OO event display program based onHEPVis.Figure 5 – L3/CMS extensions to the standard GUI for controlling visibility.  Now this functionality can beinvoked from the main menu bar in the standard HEPVis fashion.The Northeastern University group (G. Alverson, T. Paul, L. Taylor, and S. Villa) are using and extendingthe HEPVis library to create new event display programs for the L3 and CMS experiments. Figure 4 showsan example of the L3 prototype showing the L3 detector, based on new classes for GEANT3 detectorvolumes for tracks, energy towers in the crystal calorimeter, clusters in the HCAL, and reconstructed jets.Figure 5 shows extensions to the user interface for controlling the visibility using a tree-like visibilitywidget constructed automatically from the tree-like organization of the Inventor scene.   RecentlyNortheastern (G. Alverson) has become active in the D0 effort to produce a new event display for Run IIbased on HEPVis.5. HEPVis Recent ActivityOther current activity using HEPVis includes:• MCFast (A. Boehnlein)4• Geant4 (G. Barrand, J. Boudreau, J. Kallenbach)5• Prototyping at D0 (various), Muon Collider (P. Lebrun), Minos (J. Kallenbach)• Virtual reality demonstration at FNAL (J. Kallenbach, A. Kubarovsky)6• SND (I. Gaponenko)7Recent improvements to the library include:• SbAxis – Axis base class• SbGraphicContext – Graphics context including font, linestyle, fill style, etc.• SmPushButton – Complete pushbutton class, derived from trd• SoPlotter – Histogram class• SoGrid – Grid class derived from SoShape• SoTextHershey – Provides the capability to mix English and Greek text• Win32 Port• Lots of Optimization of picking and rendering• Collaboration and source code controlFigure 6 shows a demonstration of the use SoPlotter, SmPushButton, SoGrid, and SbAxis classes toconstruct and plot a histogram in an Open Inventor window.Figure 6 – Histogram in OpenInventor using SoPlotter, SbAxis, SmPushButton6. Hepvis FutureWe expect the near future to be busy.  At FNAL, we will be finishing the port to Linux KCC, and hoping tomake the product an integral part of CDF and D0 as well as other experiments such as Minos and Btev.  Wehope to complete the Geant4 shape list as well.  Of major importance will be the merging of the efforts ofour users/collaborators.  We plan to help those who are using the library to get their fixes/extensions intothe future releases.  The code is now under cvs control, and anyone who has something to contribute shouldmake contact and we’ll grant them access to the repository.7. HEPVis Availability• Platforms• IRIX 5, 6 - CC, KCC, NT - VC++, Linux (g++), Digital Unix (cxx)• To get the library:• Users - http://www-pat.fnal.gov/graphics/hepvislib.html• Collaborator information, picture gallery, etc.: http://cactus.phyast.pitt.edu/~joe/hepvis/hepvis.html8. References1. Open Inventor is a trademark of Silicon Graphics, Inc. and Template Graphics Software, Inc.2. Open GL is a trademark of Silicon Graphics, Inc.3. See http://l3www.cern.ch/~taylorl/l3scan/4. See http://fnpspa.fnal.gov/mcfast.html5. See http://asdwww.cern.ch/asd/geant/geant4.html6. See http://fnpspa.fnal.gov/virt/7. See http://www.inp.nsk.su/snd

Status of the HEPVis class library

Status of the HEPVis class library

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