Session 4B: VRML, Java, and Virtual Reality     

This session provides a brief introduction to VRML, the Virtual Reality Modeling Language.  We illustrate how VRML can be used in conjunction with Java and describe the benefits of incorporating VRML into a computer science curriculum.  We conclude with an introduction to virtual reality (VR) technologies and the role that VRML and Java play in the development ov VR applications.  This session provides a basic background for the subsequent demonstrations  in the UITS Advanced Visualization Lab during Session 5.
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Outline

1. VRML - What, When, Why, and Why Not
2. VRML and Java
   
3. Virtual Reality
   
4. Resources
   

1. VRML - What, When, Why, and Why Not

VRML Description (from the ISO Specification)

VRML is capable of representing static and animated dynamic 3D and multimedia objects with hyperlinks to other media such as text, sounds, movies, and images. VRML browsers, as well as authoring tools for the creation of VRML files, are widely available for many different platforms.

VRML supports an extensibility model that allows new dynamic 3D objects to be defined allowing application communities to develop interoperable extensions to the base standard. There are mappings between VRML objects and commonly used 3D application programmer interface (API) features.

Brief History of VRML

1994 - VRML1.0 standard based on SGI's Open Inventor - static models only
1997 - VRML2.0 standard (officially VRML97) based on "Moving Worlds" proposal - dynamic models and extensibility
2003 - X3D standard (eXtensible 3D, "VRML3.0") -  clarification and modularization of  VRML 97  +  expanded capabilities
-- We'll be refering to the VRML97 standard in these notes.

VRML Examples

• static VRML model - Supercomputing Conference exhibit booth (VRML 1.0) MIR space station (VRML2.0)
  
• animated VRML model - Groundwater flow simulation
  
• VRML embedded with HTML - CyberAstronomy (developed by SGI)
  
  

Benefits of VRML for teaching Computer Science

• Open Standard - refined be the collective wisdom of expert user community
• Widely supported - static file VRML file import and export in most 3D packages and visualization tools
  
• ASCII encoding -> many possible developer interfaces
• GUI Editors
• Text Editors
• Translation programs (Java or Perl)
• combinations of the above
• Motivating - 3D graphics, audio, media files; immediate feedback; visual debugging
• Gradual exposure to programming - modeling -> animation -> interaction -> scripting -> programming
  
• Object-Oriented concepts - objects (nodes), fields, input/output interfaces (routes), abstraction and inheritence (protos), etc.
• Other applied concepts - data structures (trees, stacks, etc), 3D math, linear algebra, etc.
  
• Lots of resources - content components, examples, tutorials, and tools

Why not use VRML?

• Relatively complex standard - lots of features and functionality
• Lacks comprehensive debugging tools
  
• May not scale well to complex problems - becomes very "kludgey" for certain types of applications
  
• Event and execution model is less explicit than procedural languages
  
• Fewer robust tools outside of MS Windows
• Evolving standard
  
• moving target (X3D)
  
• competing, proporietary technologies are quicker with new features
  

2. VRML and Java

VRML Scene Graph Structure

• A snippet of VRML "code"
• The conceptual scene graph equivalent
• The resulting 3D world

More than just objects, appearances, and transformations

• Interpolators vary position, orientation, color, shapes, etc. over time
• Sensors detect and respond to user actions and control timers
  
• Node outputs may be ROUTEd to node inputs creating explicit chains of events
• special working group extensions for GIS (GeoVRML), humanoid animation (H-ANIM), MPEG4, etc.
  

Programming VRML with Java - 3 Possible methods:

• VRML Script Node
• JavaScript/VRMLscript/ECMAscript - interpreted at runtime
• Java - precompiled classes
• both methods (Java/VRML/ECMAScript & Java) are supported in most commercial browsers
• examples: simple orrery, animation with playback control
  
• VRML EAI  (External Authoring Interface)
• Java classes for interacting with the VRML browser from an external Java applet
• powerful, but requires the right combination of Web browser, VRML browser, and Java
• example - astronomy visualization tool (screen shot)
  
• VRML implemented (in whole or in part) within another programming environment
• VRML loader for Java3D
• VRML classes in Java, C++, and other scene graph libraries
• usually no execution model -> developer must implement that in the native language
  

Programming X3D with Java - promises more possibilities

• lightweight X3D viewers in Java only
• full X3D browsers written in Java3D - www.xj3d.org

3. Virtual Reality

Characteristics of a VR system

• immersive - wide field of view -> wide screen or head-mounted display
• stereographic
• interactive
• first person perspective -> head tracking
• natural interaction -> hand/body tracking
• multi-modal - visual + audio, haptic

VR Displays

• CAVE - fully immersive display
  
• ImmersaDesk / John-e-Box - semi-immersive, single-screen displays
  
• Haptic Workstation - couples force feedback with graphics
  

So, VRML is ideal for VR displays, right?

• Not really. 
  
• VRML is great as a rapid prototyping tool, but issues with device drivers, multi-processing, and synchronization make it cumbersome for more complex applications and VR.
• A few successful VRML-based tools:
• CAVE6U browser for CAVEs - covers ~ 90% of the standard
• VRML97 is the basis for haptics API from Reachin, Inc.

So, how do people program for VR?

• OpenGL + C + VR Library
• OpenPerformer (visual simulation scene graph library) + C++
• YG (scripting language built on top of Performer)
• Java3D - with many custom extensions (U. of Calgary)

VR Demos:

• Crayoland - simple VR environment using OpenGL - audio, animation, interaction
  
• 3DIVE - scientific visualization application - natural interaction, volume rendering
  
• Mission to MIR - VRML content in CAVE6U browser - "Gorby" visit in `97
  
• Reachin Haptic Display - simple environments coupling graphics with force feedback - VRML-based API
  
  

4. Resources

• Web3D Consortium (www.web3d.org) - home to VRML and X3D standards
  
• VRML97 specification
• VRML Repository of Content, Tools,  and Applications
• ParallelGraphic's Cortona VRML Browser
  
• Annotated VRML97 Reference Manual (complete book online)
  
• Dave Nadeau's VRML97 course notes (SDSC)