Introduction to Virtual Reality

History of Web3D

Review Progress

1. VRML97
2. Consortium's first attempts at a DTD: 1998 - 2000
3. Community's first attempts at a Schema: 2001 - 2003
4. xVRML Project: 2003 - Present

Why VRML97 was good, and why it was problematical

Learning curve, notational scheme, stock of knowledge at hand

Why not the X3D DTD or Schema?

• complexity
• size
• committees build monsters

• Current X3D DTD
• Current X3D Schema

xVRML Standard Intro

The xVRML Specifications are based on the xVRML Schema, which in turn provides a "model" of the data in a virtual reality instance document (or "world"). The xVRML Schema & Specifications also form the basis for the development of "view" and "controller" software technologies to express xVRML instance documents.

In the end, xVRML is simply XML. Just as a webpage is just data for a 2D display structured by HTML tags, so an xVRML file is just data for a 3D display structured by xVRML tags. Classroom experience has taught that, if someone can read and understand .html files, then they can also read and understand .xwrl files.

xVRML scenes can be distributed across the Internet, and can currently be viewed in a free-standing application. A set of complimentary browser plugins is planned. xVRML provides all the features of a basic VR language, and only requires a text editor to create and modify objects and scenes.

xVRML works with standard Schema-aware XML editors. xVRML is simple, lightweight, easy to read, and easy to understand.

• Current xVRML Schema

Object Representation

Objects in 3D are defined by:

• points in three-dimensional space ("3-space")
• lines linking the points to create faces
• surface qualities applied to faces (colors, textures, shininess, etc.)

Position and Orientation

The Web-pages you are used to building are essentially two-dimensional (2D). VR is an attempt to impose a sense of three-dimensionality onto that 2D surface.

Coordinate System

The three dimensions in VR are known as X and Y and Z. X goes left-right from the origin (0.0 0.0 0.0), Y goes up-down from the origin, and Z goes in-out of the screen. Positive X is to the right, positive Y is up, and positive Z is out from the screen. A good discussion of this can be found here.

We use what is known as a "right-handed coordinate system" to visualize things. Hold up your right hand like the picture to the right, with your forefinger (Z) pointing towards you to help with your visualization.

Transform Node Details

• translation
  • review right-handed coordinate system
• rotation
  • review radians vs degrees
  • remember that pi = 180° = 3.14159
• scale

Sample xVRML Code

BallWorld.xwrl

<?xml version="1.0" encoding="UTF-8"?>
<World xmlns="http://www.xvrml.net/schemas/core"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://www.xvrml.net/schemas/core
  http://xvrml.net/schemas/xVRML.xsd" headlight="false">
  <WorldInfo>
    <title>Ball World</title>
    <info>A simple nested-transformations test</info>
    <info>2005 Jeff Sonstein</info>
  </WorldInfo>
  <children>
    <DirectionalLight/>
    <Transform name="aBall" translation="-2.0 0.0 -5.0">
      <children>
        <Shape name="redBall">
          <appearance>
            <Material>
              <diffuseColor red="1.0" green="0.0" blue="0.0" alpha="1.0"/>
            </Material>
          </appearance>
          <geometry>
            <Sphere radius="1.0"/>
          </geometry>
        </Shape>
      </children>
    </Transform>
  </children>
</World>
    

Node Groupings

• grouping nodes (defining coordinate spaces)
• common nodes (lights, sounds, routes, etc)
• sensors (click, proximity, etc)
• geometry (boxes, spheres, cylinders, etc)
• appearance (shininess, color, etc)
• interpolators (for keyframe animations)

Basic Geometry

• Box
• Sphere
• Cone
• Cylinder
• IndexedFaceSet

Documentation

Visit the xVRML Schema documentation.

Lighting Model

A good discussion of the lighting model may be found here. Note that there are no shadows and no reflections (you have to fake those).

Objects, Sets & Scenes

• similarities to constructing a play or a video
• discussion
  • what is a set?
  • what is a scene?
  • what is a world?