Chapter 2
Key Concepts

2.1 Intro
2.1.1 Overview
2.1.2 TOC
2.1.3 Conventions

2.2 Overview
2.2.1 File Structure
2.2.2 Header
2.2.3 Scene graph
2.2.4 Prototypes
2.2.5 Routing
2.2.6 Generating files
2.2.7 Presentation
     & Interaction
2.2.8 Profiles

2.3 UTF-8 syntax
2.3.1 Clear text
2.3.2 Statements
2.3.3 Node
2.3.4 Field
2.3.5 PROTO
2.3.6 IS
2.3.7 EXTERNPROTO
2.3.8 USE
2.3.9 ROUTE

2.4 Scene graph
2.4.1 Root nodes
2.4.2 Hierarchy
2.4.3 Descendants
       & ancestors
2.4.4 Hierarchy
2.4.5 Units & coord sys

2.5 VRML & WWW
2.5.1 MIME type
2.5.2 URLs
2.5.3 Relative URLs
2.5.4 data:
2.5.5 Scripting protocols
2.5.6 URNs

2.6 Nodes
2.6.1 Intro
2.6.2 DEF/USE
2.6.3 Geometry
2.6.4 Bboxes
2.6.5 Grouping & children
2.6.6 Lights
2.6.7 Sensors
2.6.8 Interpolators
2.6.9 Time nodes
2.6.10 Bindable children
2.6.11 Textures

2.7 Field, eventIn,
     & eventOut

2.8 PROTO
2.8.1 Declaration
2.8.2 Definition
2.8.3 Scoping

2.9 EXTERNPROTO
2.9.1  Interface
2.9.2  URL
2.9.3 Extensions

2.10 Events
2.10.1 Intro
2.10.2 Routes
2.10.3 Execution
2.10.4 Loops
2.10.5 Fan-in & fan-out

2.11 Time
2.11.1 Intro
2.11.2 Origin
2.11.3 Discrete/cont

2.12 Scripting
2.12.1 Intro
2.12.2 Execution
2.12.3 Initialize/shutdown
2.12.4 eventsProcessed
2.12.5 Direct outputs
2.12.6 Asynchronous
2.12.7 Languages
2.12.8 EventIns
2.12.9 fields & events
2.12.10 Browser interface

2.13 Navigation
2.13.1 Intro
2.13.2 Navigation
2.13.3 Viewing
2.13.4 Collisions

2.14 Lighting
2.14.1 Intro
2.14.2 'off'
2.14.3 'on'
2.14.4 Equations
2.14.5 References

Chapter 2 Key Concepts

This chapter describes key concepts related to the definition and use of the VRML specification. This includes syntax fundamentals, how nodes are combined into scene graphs, how nodes receive and generate events, how to create new node types using prototypes, how to distribute and share new nodes, how to incorporate user-programmed scripts into a VRML file, and various general topics on nodes.

2.1 Introduction

2.1.1 Overview

This chapter describes key concepts of the definition and use of the VRML standard. This includes how nodes are combined into scene graphs, how nodes receive and generate events, how to create node types using prototypes, how to add node types to VRML and export them for use by others, how to incorporate scripts into a VRML file, and various general topics on nodes.

2.1.2 Table of contents

See table at left for contents for this chapter.

2.1.3 Conventions used in this document

The following conventions are used throughout this standard:

Italics are used for event and field names, and are also used when new terms are introduced and equation variables are referenced.

A fixed-space font is used for URL addresses and source code examples. VRML file examples appear in bold, fixed-space font.

Node type names are appropriately capitalized (e.g., "The Billboard node is a grouping node..."). However, the concept of the node is often referred to in lower case in order to refer to the semantics of the node, not the node itself (e.g., "To rotate the billboard...", "A special case of billboarding is...").

Throughout this document references are denoted using the "[ABCD]" notation, where "[ABCD]" is an abbreviation of the reference title that is described in detail in the Bibliography.