X3D and HTML5 Summary

Status: these are the X3D and HTML5 working-group slides presented to the HTML Working Group during Technical Plenary Week (TPAC) 2009. These slides are also available in .pdf form.

Family of X3D Specifications

• X3D Abstract Specification describes basic functionality of how X3D works
• Three file formats are available
  • XML (.x3d) with XML Schema and also DTD
  • ClassicVRML (x3dv)
  • Compressed Binary Encoding (.x3db) with geometric compression and Fast Infoset (FI)
• High-performance Application Programming Interfaces (APIs) are defined for Ecmascript-264 (Javascript) and Java

X3D Strengths

• Non-profit Web3D Consortium maintains and extends X3D via working groups
• Set of International Standards certified over 12-year period by multiple national bodies in ISO
• Multiple implementations are available (open and commercial source)
• Numerous resources available online, including specifications themselves
• Third-generation 3D graphics language that extends predecessor Virtual Reality Modeling Language (VRML97)
• Long-time W3C member and contributor

Web3D Consortium has formal liaisons and working partnerships with other key organizations

• International Organization for Standardization (ISO)
• World Wide Web Consortium (W3C)
• Open Geospatial Consortium (OGC)
• The Khronos Group
• Digital Imaging and Communications in Medicine (DICOM)

Relationships between 3D scene graphs, APIs and render layers

• Scene graphs are high-level declarative models about how geometry is constructed, colored and animated; these can be expressed as an XML tree
• APIs are mid-level libraries for programmers to create imperative source code about geometry and animation (various proprietary codebases, perhaps WebGL or O3D)
• Render layers are low-level software libraries that expose the functionality of graphics hardware (e.g. OpenGL and DirectX)
• Numerous other 3D technologies exist at each these other layers, often in the form of codebases
• The X3D Specifications include both declarative models and strongly typed APIs

Similarities between MathML, SVG, and X3D

• MathML describes mathematical expressions and then renders a presentation of them
• Scalable Vector Graphics (SVG) describes and presents renderings of 2D shapes, with optional animation and interaction
• Extensible 3D (X3D) describes and presents renderings of 3D shapes, with optional animation and interaction
• All three languages are formally specified and have well-developed XML encodings
• Authors want to use these languages for multimedia content in HTML pages

X3D scene graph APIs

• X3D Scene Access Interface (SAI) provides functionally consistent standardized high-performance APIs
• X3D SAI has Ecmascript and Java bindings, other programming languages can be added
• X3D SAI is functionally equivalent and has same expressive power as file formats (.x3d, .x3dv, .x3db)
• Document Object Model (DOM) is also legal (X3D is XML after all) but historically has been infrequently used because of low performance

Differences with underlying render layers

• OpenGL, DirectX, others are used as render layers for output of X3D player which parses .x3d XML files and draws them
• Unlikely that all browsers will implement the same render layer (OpenGL ≠ DirectX)
• A Canvas3D layer might be helpful to unify calls to the underlying render layer - but how will it evolve over time?
• Not clear that Web authors are clamoring for ability to program low-level OpenGl (or similar) source code in Javascript, such models are not interoperable or composable
• X3D avoids these problems as a declarative scene-graph language available in XML

Simple X3D and HTML5 examples

Detailed example source is provided on the X3D and HTML5 examples page.

• X3D scene as external reference (Anchor link)

  HTML source:  Here is my <a href='HelloWorld.x3d' title='Link to new X3D document'>HelloWorld example</a> in X3D.

• X3D embedded in object tag

  HTML Object Tag for X3D shows how to place X3D objects within an HTML page

• HTML5 with embedded X3D as mixed-namespace document

  X3Dom demonstration

X3DOM.org implementation

• Open Source, Javascript / WebGL based
• Needs Firefox/WebKit nightly builds
• Runs without any plugin
• Can be easily modified while evolving
• Needs XHTML encoded data, one line script per XHTML

X3DOM.org functionality

• Searches for existing <X3D xmlns= > and creates scenegraph from DOM Tree
• Creates canvas with WebGL-Context for rendering
• Monitors changes with DOM Level 2 events (DOMNodeRemoved, DOMNodeInserted, DOMAttrModified)
  • DOMAttrModified buggy in WebKit !!!
• Supports simple interaction (HTML events on 3D Object) and navigation

X3DOM.org status

• 3 work-months of development
• Manageable Code Size (~5000 Lines JavaScript Code, ~1000 Lines GLSL Shader Code)
• Support well defined Subset of X3D
  • Interchange Profile + Inline, Scripting, Text nodes
  • No Scripting or Prototype on the X3D side
• Dynamic X3D content
  • Support for n:m FieldToField ROUTEs, TimeSensor + Interpolator + Follower nodes

X3DOM.org solution considerations

• Provides an experimental open-source runtime – not the ultimate solution
  • Feature Limitations: e.g. no access to spatial audio or video texture layer
  • Performance Limitation: Javascript/WebGL can only handle models up to ~200.000 Triangle right now
• Standardization and native implementations are needed
  • Support for SAI/X3D-Plugin in addition to the WebGL-Render backend will be next iteration
  • Final deployment solution best as part of browser
  • X3D community has multiple open-source C/C++ codebase resources available

Lessons learned from years developing the FreeWrl X3D player

• Experience: FreeWRL was originally interpreted Perl with specialized "C" functions. Hoped that hardware would improve faster than size of models; that was not the case.
• Interpreted was not the way to go, rewritten in C for performance
• Differing OpenGL capabilities: X3D Browsers can handle these, so older models can run efficiently on new hardware (write once, run anytime; even VRML1 models from NASA run fast now)
• X3D models are not tied to specific hardware, can run over OpenGL-ES, OpenGL-3.2, DirectX11, older standards like OpenGL-1.0...
• OpenGL requires significant programming skills. Don't know why the average web author would want to code in OpenGL.
• What does FreeWRL require from Web browser or window? An OpenGL Context (i.e. a number); mouse and keyboard events, window size events, that's about it.

Action items for X3D and HTML5

• Ensure proper X3D references in HTML5 specifications - what happened, what happens next?
• How to allow X3D scene to either reserve screen space or float over the page? Presumably CSS, X3D elements include the class attribute
• X3D version 3.3 draft is considering SVG and HTML as source for image textures; how to pass events?
• X3D compression will likely evolve to use Efficient XML Interchange (EXI)
• Web Accessibility is a future interest
• Continue to document correct integration and best practices for X3D and HTML5

Conclusions

• X3D Graphics is a natural fit for HTML5
• We want to maximize capabilities and deployment
• Further collaboration welcome