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Developing VR Applications with the inVRs Framework at IEEE VR’10 Part I – Introduction

Developing VR Applications with the inVRs Framework at IEEE VR’10 Part I – Introduction. Overview. Introduction System Core User Database World Database Event Manager Transformation Manager Interfaces Input Interface Output Interface Modules Navigation Interaction Network Outlook

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Developing VR Applications with the inVRs Framework at IEEE VR’10 Part I – Introduction

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  1. Developing VR Applicationswith the inVRs Frameworkat IEEE VR’10Part I – Introduction

  2. Overview • Introduction • System Core • User Database • World Database • Event Manager • Transformation Manager • Interfaces • Input Interface • Output Interface • Modules • Navigation • Interaction • Network • Outlook • Acknowledgements Developing VR Applications with the inVRs Framework

  3. Introduction and Architecture Overview Developing VR Applications with the inVRs Framework

  4. Introduction • inVRs(interactive networked Virtual Reality system) • Pronounced • C++ application framework for Networked Virtual Environments (NVEs) • Publicly available under www.invrs.org (under LGPL) • Uses Trac system for distribution • Alternatively latest stable release as zip • Windows binary available as well • Available for Linux, Windows, Mac OS X, and maybe IRIX • Variety of out-of-the-box Features • Network communication supporting close coupled collaboration • Clear definition for navigation and interaction (with many techniques provided) • Designed for reusability of developed components • Easy-to-use configuration for immersive devices Developing VR Applications with the inVRs Framework

  5. Introduction • Documentation available on Trac System • Several publications (BiBTeX files) • Tutorial examples • Medieval Town Tutorial and Going Immersive Tutorial • Programmers’ Guide (coming soon) • Doxygen (http://doxygen.invrs.org/) • Libraries • Required • OpenSG v1.8 (http://www.opensg.org/) • GMTL distributed with source (http://ggt.sourceforge.net) • IrrXML distributed with source (http://www.ambiera.com/irrxml/) • CMake (http://www.cmake.org/) • Optional • OpenAL and ALUT (http://www.openal.org/) • ODE (http://www.ode.org/) • trackD (with CAVELib), VRPN (http://www.cs.unc.edu/Research/vrpn/) Developing VR Applications with the inVRs Framework

  6. Introduction • Where to position inVRs in the development approaches for VR applications • Graphical Editors (using software components) • (e.g. VirTools, Quest3D) • VR systems incorporating scripting languages • (e.g. DIVE, ALICE, AVOCADO) • Application Frameworks • (e.g. VRJuggler, instantreality) • Scene Graphs • (e.g. OpenSG, OpenSceneGraph) • Full development from scratch via C or C++ • OpenGL presents comparably high effort for new development of VR applications Developing VR Applications with the inVRs Framework

  7. Introduction • Application Areas Collaborative Work Entertainment Safety Training Art Scientific Visualization Education Architecture Visualization Product Presentation World Layout Developing VR Applications with the inVRs Framework

  8. Introduction • inVRs consists of the following components • Interfaces (designed for flexible extension) • Modules (designed as plug-ins for exchangeability, modularity) • System Core (not to be changed in structure, provides many extensible, exchangeable sub-components) • Communication in the diagram happens typically top-down Developing VR Applications with the inVRs Framework

  9. System Core Developing VR Applications with the inVRs Framework

  10. System Core • Acts as glue • Internally between communication units and database units • Externally to interfaces and modules • Core functionality • Data types • Configuration handling (parsing and updating of XML configuration) • Logging (used for profiling application parts) • Timer (common timer for all inVRs components) • Interfaces (interfaces to modules and other inVRs components) • ID management (unique ID handling) • Application base (used for simplification of the development process) • Contains subcomponents for database handling and message handling • User and world database are used for VE storage • Event and transformation manager are used for communication Developing VR Applications with the inVRs Framework

  11. System Core - User Database Developing VR Applications with the inVRs Framework

  12. System Core - User Database • Stores information about users • Local user • Remote users • Settings for user dependent application behavior • User Representation • Cursor Representation • User Transformation • Cursor Transformation • Coordinate Systems • Origin of the VE • Navigated transformation • User transformation • Hand transformation • Head transformation Developing VR Applications with the inVRs Framework

  13. System Core - User Database • Different models for representation are available • User Representation • Simple Avatar • Simple textured geometry not articulated • Avatara Avatar • Use of mesh skinning for animations • Separate control of head, back and hand • More detail in Going Immersive Tutorial • Cursor Representation • Simple Cursor • Basic textured geometry displayed at cursor position • Interaction Cursor • Illustrates the state of interaction (idle, selection, manipulation) • Implemented by switching through three different graphical representations Developing VR Applications with the inVRs Framework

  14. System Core - User Database • Different models for user and cursor behavior are available • User Transformation • Defines the user transformations • Has to be modified e.g. if tracking systems are used • Cursor Transformation • Defines behavior of the user cursor • Might have to be altered to implement specific interaction technique • Models are available for • Virtual Hand • HOMER Developing VR Applications with the inVRs Framework

  15. System Core - World Database Developing VR Applications with the inVRs Framework

  16. System Core - World Database • Keeps information about the objects of the virtual world • Initially designed to partition the VE • Partitioning idea relates to network scalability concepts • Supports as well frustum culling of the underlying scene graph • Partitioning concept ideal for 2D layout of the scenes, usable in 3D applications as well • Important objects for structuring • Entities and entity types • Objects in a VE and their type • Tiles • Element used to partition the VE • Environment and environment layout • Describes a local coordinate system and the layout of several coordinate systems Developing VR Applications with the inVRs Framework

  17. System Core - World Database • World Database - Scene Graph Representation • Data is stored inside STL vectors • Mapping of object IDs via hash tables for improved seek performance • IDs stored in ID pools Developing VR Applications with the inVRs Framework

  18. System Core - Event Manager Developing VR Applications with the inVRs Framework

  19. System Core - Event Manager • Used for handling and distribution of discrete events • Handles discrete communication • Components can register via piping mechanism to the event manager • Events are generated by components • Sent to an event pipe in the event manager • They can be filtered in the pipe (partially implemented) • Events are stored in event queues • Receiving components poll their queues • Events are executed inside the components • Depending on the visibility level (LOCAL, REMOTE, GLOBAL) of the messages they are sent to the network module (if available) and are distributed in a reliable manner (typically via TCP) Developing VR Applications with the inVRs Framework

  20. System Core - Event Manager • Conceptual Approach Developing VR Applications with the inVRs Framework

  21. System Core - Transformation Manager Developing VR Applications with the inVRs Framework

  22. System Core - Transformation Manager • Used for handling and distribution transformation data • Handles continuous flow of transformation data packets • Transformation Matrices • Common type of data in VEs besides events are transformation matrices (navigation, object manipulation) • Vast amount of transformations are present because of the use of position tracking devices • Transmission not necessarily reliable • Manager has several pipes with source and destination • Every object which is to be transformed in the VE gets it‘s own pipe which is opened at the start of the transformation • Transformations are applied typically on the database of the VE and are (if available) partially transferred via the network module in an unreliable manner • Each pipe can have an arbitrary amount of stages • Each stage contains one transformation modifier • The pipe stages are predefined at application setup • Once per frame all pipe stages on each pipe are computed Developing VR Applications with the inVRs Framework

  23. System Core - Transformation Manager • Pipe stages contain transformation modifiers which are set up by the application developer • If more than one transformation pipe exists for a single object the transformations are processed to one resulting transformation • Implemented as a merger modifier • Transformation Modifiers • Various modules can influence the transformation pipes via the modifiers • Network, interaction, navigation, physics, collision detection, … • Pipe Stages – Different types of modifiers can be applied • Modifiers • Modify pipe content, can write values to other inVRs components • Writers • Write values to other inVRs components, do not modify pipe content • Mergers • Used to merge pipes • Interrupters • Pipes have to be interrupted after merging Developing VR Applications with the inVRs Framework

  24. System Core - Transformation Manager • Transformation Manager – Program Flow Developing VR Applications with the inVRs Framework

  25. Interfaces - Input Interface Developing VR Applications with the inVRs Framework

  26. Interfaces - Input Interface • Input Interface • Used for the abstraction of input devices • Important since it is not often possible to develop on the VR installation and in case of Networked Virtual Environment seldom similar installations are interconnected • Low-level device drivers or high-level libraries can be used for gathering input Developing VR Applications with the inVRs Framework

  27. Interfaces - Input Interface • Input Interface • Data of the input devices is exposed in a unified form (buttons, sensors, axes) as an abstract controller • This abstract controller can be accessed by inVRs components like modules or core components Developing VR Applications with the inVRs Framework

  28. Interfaces - Output Interface Developing VR Applications with the inVRs Framework

  29. Interfaces - Output Interface • Output Interface • Used for the abstraction of output devices • Interface to common scene graphs (OpenSG, OpenSceneGraph) and audio library (only partially implemented yet) • Use of OpenSG allows easy rendering on arbitrary multi-display installations Developing VR Applications with the inVRs Framework

  30. Modules - Navigation Developing VR Applications with the inVRs Framework

  31. Modules - Navigation • Navigation Module – Architecture • Transformation results from speed, direction and orientation • These three components are individually configurable Developing VR Applications with the inVRs Framework

  32. Modules - Interaction Developing VR Applications with the inVRs Framework

  33. Modules - Interaction • Interaction Module • Different interaction techniques exist e.g. • Virtual Hand (aka Natural Interaction) • Most common interaction technique in VR • Direct mapping of cursor transformation for selection and manipulation • HOMER • Combination of ray-casting for selection und Virtual Hand for manipulation at distance • GoGo • Non-Linear scaling of distance vector between user sensors for determination of the cursor transformation • Interactions techniques can be split up into individual reusable components for different parts of the interaction Developing VR Applications with the inVRs Framework

  34. Modules - Interaction • Interaction Module is implemented as an automaton • Input alphabet Σ defined through components of abstract controller and system states • q = {q0 (Idle), q1 (Selection), q2 (Manipulation)} • Transition functions δ defined through components of interaction techniques • Begin and end state = q0 Developing VR Applications with the inVRs Framework

  35. Modules - Interaction • Collaborative interaction from a scene graph perspective • Collaborative interaction allows concurrent manipulation of an object through several users at the same attribute (typically transformation matrix) • Having more than one parent nodes in a scene graph (if allowed) lead to multiple rendering of an object • Transformation changes initiated by different sources, which refer to the same object are detected as a conflict an resolved with the help of the transformation manager Developing VR Applications with the inVRs Framework

  36. Modules - Network Developing VR Applications with the inVRs Framework

  37. Modules - Network • Network Module • General problem with network solutions is their ambivalence • Thus the inVRs network module is designed for exchangeability • Consists of two layers • High-Level: general interface to the framework • Low-Level: implementation of network communication and topology • Different implementations of the low-level layer exist • Separation of the virtual world on different servers (e.g. via Grid computing) • Standard implementation of the network module uses peer-to-peer communication and topology • Typically events are distributed via TCP (reliable) and transformation data is distributed via UDP (unreliable but fast) Developing VR Applications with the inVRs Framework

  38. Outlook Developing VR Applications with the inVRs Framework

  39. Outlook • Additional Tools Joint Interaction Avatars Physics Module 3D Menus Particle System Wrapper Height Maps Collision Maps CAVE Scene Manager Free Form Deformation Module Developing VR Applications with the inVRs Framework

  40. Outlook • Novel concepts • Clear distinction in the area of communication patterns • Events and transformations are handled independently • Transformation management allows for concurrent object manipulation • Composeable and clearly defined interaction and navigation • Automatic data distribution mechanism • Next slide sets • Medieval Town Tutorial • Going Immersive Tutorial Developing VR Applications with the inVRs Framework

  41. Acknowledgements • Contributors • Architecture and Main Development Christoph Anthes, Helmut Bressler, Roland Landertshamer, Marina Lenger • Tools Helmut Garstenauer, Martin Garstenauer, Adrian Haffegee, Marlene Hochrieser, Roland Hopferwieser, Robert Owen, Stephan Reiter, Thomas Weberndorfer, Christian Wressnegger, Johannes Zarl Developing VR Applications with the inVRs Framework

  42. Questions ?

  43. Bibliography • Christoph AnthesA Collaborative Interaction Framework for Networked Virtual Environments. PhD Thesis at Institute of Graphics and Parallel Processing at JKU Linz, Austria, August 2009. • Christoph Anthes, Philipp Aumayr, Clemens Birklbauer, Roland Hackl, Marlene Hochrieser, Roland Hopferwieser, Simon Opelt, Christoph Payrhuber, Mika Satomi, Stefan Simmer, Georg Stevenson, Roland Landertshamer, Bernhard Lehner, Marina Lenger, Martin Lenzelbauer, Clemens Mock, and Alexander Wilhelm.Space Trash – Development of a Networked Immersive Virtual Reality Installation. Technical Report at Institute of Graphics and Parallel Processing, Johannes Kepler University Linz, June 2009. • Christoph Anthes, Mika Satomi, Alexander Wilhelm, Christa Sommerer, and Jens Volkert. Space Trash – An Interactive Networked Virtual Reality Installation. In Proceedings of the 11th Virtual Reality International Conference (VRIC ’09), pages 107-118, Laval, France, April 2009. • Christoph Anthes, Mika Satomi, Alexander Wilhelm, Christa Sommerer, and Jens Volkert. Design and Setup of Space Trash – A Collaborative Virtual Reality Installation using Physical Interfaces. Installation description in Proceedings of the 11th Virtual Reality International Conference (VRIC ’09) ReVolution, pages 355-362, Laval, France, April 2009. Developing VR Applications with the inVRs Framework

  44. Bibliography • Christoph Anthes, Roland Landertshamer, Helmut Bressler, and Jens Volkert.Developing VR Applications for the Grid. In 1st International Workshop on Real–Time Online Interactive Applications (ROIA) on the GRID at the 14th International Euro-Par Conference European Conference on Parallel and Distributed Computing (Euro-Par ’08), pages 343–351, Las Palmas de Gran Canaria, Spain, August 2008. • Eva Pajorová, Ladislav Hluchý, and Christoph Anthes.3D Geovisualization Service for Grid-oriented applications of Natural Disasters.Poster in the 16th International Conference in Central Europe on Computer Graphics, Visualization and Computer Vision (WSCG '08), Plzen, Czech Republic, February 2008. • Christoph Anthes, Alexander Wilhelm, Roland Landertshamer, Helmut Bressler, and Jens Volkert.Net’O’Drom – An Example for the Development of Networked Immersive VR Applications. In International Conference on Computational Science (ICCS '07), pages 752-759, Beijing, China, May 2007. • Christoph Anthes, Roland Landertshamer, and Jens Volkert.Physically-Based Interaction for Networked Virtual Environments. In International Conference on Computational Science (ICCS '07), pages 776-783, Beijing, China, May 2007. Developing VR Applications with the inVRs Framework

  45. Bibliography • Christoph Anthes, Roland Landertshamer, Helmut Bressler, and Jens Volkert.Managing Transformations and Events in Networked Virtual Environments. In ACM Multimedia Modeling (MMM '07), pages 722-729, Singapore, January 2007. • Helmut Bressler, Roland Landertshamer, Christoph Anthes, and Jens Volkert.An efficient Physics Engine for Virtual Worlds. In medi@terra, pages 152-158, Athens, Greece, October 2006. • Christoph Anthes and Jens Volkert.inVRs - A Framework for Building Interactive Networked Virtual Reality Systems. In International Conference on High Performance Computing and Communications (HPCC '06), pages 894-904, Munich, Germany, September 2006. • Christoph Anthes, Adrian Haffegee, Paul Heinzlreiter, and Jens Volkert.A Scalable Network Architecture for Closely Coupled Collaboration. In Journal of Computing and Informatics, 24(1):31-51, August 2005. • Christoph Anthes and Jens Volkert.A Toolbox Supporting Collaboration in Networked Virtual Environments. In International Conference on Computational Science (ICCS '05), pages 383-390, Atlanta, GA, USA, May 2005. Developing VR Applications with the inVRs Framework

  46. Bibliography • Adrian Haffegee, Ronan Jamieson, Christoph Anthes, and Vassil N. Alexandrov.Tools For Collaborative VR Application Development. In International Conference on Computational Science (ICCS '05), pages 350-358, Atlanta, GA, USA, May 2005. • Christoph Anthes, Paul Heinzlreiter, Adrian Haffegee, and Jens Volkert.Message Traffic in a Distributed Virtual Environment for Close-coupled Collaboration. In Parallel and Distributed Computing and Systems (PDCS '04), pages 484-490, San Francisco, CA, USA, September 2004. • Christoph Anthes, Paul Heinzlreiter, Gerhard Kurka, and Jens Volkert.Navigation models for a flexible, multi-mode VR Navigation Framework. In ACM SIGGRAPH International Conference on Virtual Reality Continuum and its Applications in Industry (VRCAI '04), pages 476-479, Singapore, June 2004. • Christoph Anthes, Paul Heinzlreiter, and Jens Volkert.An adaptive Network Architecture for Close-coupled Collaboration in Distributed Virtual Environments. In ACM SIGGRAPH International Conference on Virtual Reality Continuum and its Applications in Industry (VRCAI '04), pages 382-385, Singapore, June 2004. Developing VR Applications with the inVRs Framework

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