1 / 22


Scope. ROOT. Light Source. Transform. Transform. Sphere. Sphere. Light Source. 3D on the Web.

Télécharger la présentation


An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.


Presentation Transcript

  1. Scope ROOT Light Source Transform Transform Sphere Sphere Light Source

  2. 3D on the Web • If you want any kind of special lighting effect on a surface, such as a spotlight with a soft edge, that surface will have to have many vertices on it and be made up of many faces, as VRML only does lighting at each corner. • This is a very important thing to remember. If you have a light shining on the middle of a large surface, you will not get the effect you want.

  3. 3D on the Web • Just as HyperText Markup Language (HTML) led to a huge increase in the use of graphics on the Internet by implementing a graphical interface • The VRML Consortium intend to add the next level of interaction, structured graphics, and extra dimensions (z and time) to the web • The VRML consortuin was created in 1994 • It has created a standard for a Virtual Reality Modeling Language (VRML) • often pronounced 'vermal’ • ISO Standardised in 96, (ISO VRML97)

  4. History • In 1994, Tim Berners-Lee invited Mark Pesce to present a paper at the First International Conference on the World Wide Web • Pesce and partner Tony Parisi had developed Labyrinth, a prototype three-dimensional interface to the Web • His presentation sparked a consensus: the conference attendees agreed there was a need for a common language to specify 3D scene descriptions • Brian Behlendorf set up an electronic mailing list to facilitate discussion of the specification for VRML

  5. History • Within a month, there were over a thousand members • The list membership quickly agreed upon a set of requirements for VRML: • platform independence • extensibility • ability to work over low-bandwidth (14.4 kBps modem) • After much deliberation, the proto-VRML community selected the Open Inventor ASCII File Format from Silicon Graphics, Inc. as the basis of VRML • Some of the leading technical experts on the VRML mail list formed the VRML Architecture Group (VAG) in 95

  6. Members • The Web3D Consortium has 42 Corporate Members, 10 Charter Members, 12 Voting Members and 20 Non-Voting Associate Members • Microsoft Corporation, Apple Computer, Silicon Graphics, Inc., Sony Corporation, Hewlett-Packard, Philips Electronics, Sun Microsystems etc

  7. Virtual Reality Modeling Language • The Virtual Reality Modeling Language (VRML) is a file format for describing interactive 3D objects and worlds • Conceptually, each VRML file is a 3D time-based space that contains graphic and aural objects that can be dynamically modified through a variety of mechanisms • VRML is designed to be used on the Internet, intranets, and local client systems

  8. Virtual Reality Modeling Language • A characteristic of VRML files is the ability to compose files together through inclusion and to relate files together through hyperlinking • e.g consider the file earth.wrl specifies a world containg a sphere representing the earth • It may also contain references to a variety of other VRML files representing cities on the earth (e.g., file paris.wrl) • earth.wrl defines the coordinate system in which all cities reside • Each city file defines its own world coordinate system that the city resides in that becomes a local coordinate system when contained by the earth file

  9. Virtual Reality Modeling Language • Hierarchical file inclusion enables the creation of arbitrarily large, dynamic worlds • Therefore, VRML ensures that each file is completely described by the objects contained within it • There are various objects and mechanisms built into the language that support multiple distributed files, including: • in-lining of other VRML files; • hyperlinking to other files; • using existing Internet and ISO standards for other file formats; • defining a compact syntax

  10. Characteristics of VRML • VRML is capable of representing • Static and animated dynamic 3D • multimedia objects with hyperlinks to other media such as • text • sounds • movies • images • VRML browsers, as well as authoring tools for the creation of VRML files, are available for a number of different platforms • See links on last slide

  11. VRML and Time • The browser controls the passage of time in a world by causing TimeSensors to generate events as time passes • Specialized browsers or authoring applications may cause time to pass more quickly or slowly than in the real world, but typically the times generated by TimeSensors will approximate "real" time • A world's creator should make no assumptions about how often a TimeSensor will generate events but can safely assume that each time event generated will have a timestamp greater than any previous time event.

  12. VRML Light • Shape nodes are illuminated by the sum of all of the lights in the world that affect them • This includes the contribution of both the direct and ambient illumination from light sources • Ambient illumination is from the scattering and reflection of light originally emitted directly by light sources • The amount of ambient light is associated with the individual lights in the scene • The following node types are light source nodes: • DirectionalLight • PointLight • SpotLight

  13. Sensor nodes • VRML contains the following concepts of sensors: • Environmental sensors • Pointing-device sensors

  14. Environmental sensors • The ProximitySensor detects when the user navigates into a specified region in the world • The ProximitySensor itself is not visible • The TimeSensor is a clock that has no geometry or location associated with it; • it is used to start and stop time-based nodes such as interpolators • The VisibilitySensor detects when a specific part of the world becomes visible to the user • The Collision grouping node detects when the user collides with objects in the virtual world

  15. Pointing-device sensors • Pointing-device sensors detect user pointing events such as the user clicking on a piece of geometry • i.e. TouchSensor • A pointing-device sensor is activated when the user locates the pointing device over geometry that is influenced by that specific pointing-device sensor

  16. Navigation • Conceptually speaking, every VRML world contains a viewpoint from which the world is currently being viewed • Navigation is the action taken by the user to change the position and/or orientation of this viewpoint thereby changing the user's view • This allows the user to move through a world or examine an object

  17. Navigation • The browser may allow the user to modify the location and orientation of the viewer in the virtual world using a navigation paradigm • Many different navigation paradigms are possible, depending on the nature of the virtual world and the task the user wishes to perform • e.g. a walking paradigm would be appropriate in an architectural walkthrough application, while a flying paradigm might be better in an application exploring interstellar space

  18. Simple Example : Output

  19. Further reading • The information in this lecture is extremely changeable so you must access the web for further reading • http://www.vrml.org/faq/faq.html • http://www.vrml.org/Specifications/VRML97/ • http://www.sgi.com/Technology/Inventor/ • http://www.hyperreal.com/~mpesce/ • http://www.ch.ic.ac.uk./talks/www94_report.html • http://www.vrml.org/vag

  20. Further reading VRML 1.0 • Standard objects (cube, sphere, cone, cylinder, text) • Arbitrary objects (surfaces, linesets, pointsets) • Ability to fly through, walk through, examine scenes • Lights • Cameras (viewpoints) • Textures on objects • Clickable links • Define and reuse objects VRML 2.0All of VRML 1.0 plus • Animated objects • Switches • Sensors • Scripts (Java or JavaScript) for behaviors • Interpolators (color, position, orientation, etc.) • Extrusions • Background colors and textures • Sound (.wav and MIDI) • Animated textures • Event routing • Define and reuse objects and behaviors and effectively add new nodes to the language with PROTO and EXTERNPROTO

More Related