The Virtual Reality Modeling Language

3. Definitions

ISO/IEC DIS14772-1

January 24, 1997

3.1 activate

To cause a sensor node to generate an "isActive" event. The various types of sensor nodes are "activated" by user interactions, the passage of time, or other events. Only active sensors affect the user's experience.

3.2 appearance node

Appearance nodes control the rendered appearance of the geometry nodes with which they are associated. A node of type Appearance, FontStyle, ImageTexture, Material, MovieTexture, PixelTexture, or TextureTransform.

3.3 author

Person or organization that creates VRML files.

3.4 authoring tool

See generator.

3.5 avatar

The abstract representation of the user in a VRML world. The physical dimensions of the avatar are used for collision detection and terrain following. See "5. Nodes Reference -NavigationInfo" for details

3.6 bindable children node

Bindable children nodes may have many instances in a scene graph, but only one instance may be active at any instant of time. A node of type Background, Fog, NavigationInfo, or Viewpoint. Also referred to as "binding node". See "4.9.1 Bindable Children Nodes" for details

3.7 browser

A computer program which interprets VRML files, presents their content to a user on a display device, and allows the user to interact with worlds defined by VRML files by means of a user interface.

3.8 browser extension

Nodes defined using the prototyping mechanism which are understood only by certain browsers. See "4.8 Browser Extensions" for details.

3.9 built-in node

A node type explicitly defined in this standard.

3.10 callback

A function defined in a scripting language to which events are passed. See "4.7.8.EventIn Handling" for details.

3.11 candidate

One of potentially several choices. The user or the browser will select one of the choices when all candidates are identified. See "5. Node Reference - Anchor" and "4.9.1 Bindable Children Nodes - Bind Stack Behaviour " for details.

3.12 children nodes

Nodes which are parented by grouping nodes and are affected by the transformations of all ancestors. See "4.3.1 Grouping and Children Nodes" for list of allowable children nodes.

3.13 collision proxy

A node used as a substitute for a Collision node's children during collision detection. See "5. Node Reference - Collision" for details.

3.14 colour model

Characterization of a colour space in terms of explicit parameters. VRML allows colours to be defined only with the RGB colour model. However, colour interpolation is performed in the HSV colour space.

3.15 culling

The process of identifying objects or parts of objects which do not need to be processed further by the browser in order to produce the desired view of a world.

3.16 display device

A graphics device on which VRML scenes can be represented.

3.17 drag sensor

Drag sensors are pointing device sensors which cause events to be generated in response to pointer motions which are sensor-dependent. For example, the SphereSensor generates spherical rotation events. A node of type CylinderSensor, PlaneSensor, SphereSensor See "4.9.6.2 Drag Sensors" for details.

3.18 event

Messages sent from one node to another as defined by a Route. Events signal changes to field values, external stimuli, and interactions between nodes. Events consist of a time stamp and a field value.

3.19 event cascade

A sequence of events initiated by a script or sensor event and propagated from node to node along one or more routes. All events in an event cascade are considered to have occurred simultaneously. See "4.5.4 Execution Model" for details.

3.20 eventIn

Logical receptors attached to a node which receive events.

3.21 eventOut

A logical output terminal attached to a node from which events are sent. The eventOut for a particular type of event also stores the event most recently sent.

3.22 execution model

The rules governing how events are processed by browsers and scripts.

3.23 exposed field

A field which can both receive events via an eventIn to change its value(s) and generate events via an eventOut when its value(s) change.

3.24 external prototype

Prototypes defined in external files and referenced by a URL..

3.25 field

The parameters that distinguish one node from another of the same type. Fields can contain various kind of data and one or many values.

3.26 field name

The name of a field. Field names are unique within the scope of the node.

3.27 file format

A detailed description of digital data which is typically stored in a computer-based file system.

3.28 frame

A single rendering of the world on a display device or one time-step in a simulation.

3.29 generator

A computer program which creates VRML files.

3.30 geometric sensor node

Geometric sensor nodes generate events based on user actions, such as a mouse click or navigating close to a particular object. A node of type ProximitySensor, VisibilitySensor. TouchSensor, CylinderSensor, PlaneSensor, SphereSensor, or Collision.

3.31 geometry node

Geometry nodes contain mathematical descriptions of three-dimensional points, lines, surfaces, text strings and solid objects. A Node of type Box, Cone, Cylinder, ElevationGrid, Extrusion, IndexedFaceSet, IndexedLineSet, PointSet, Sphere, and Text.

3.32 geometric property node

Geometry property nodes define the properties of specific geometry nodes. A node of type Color, Coordinate, Normal, or TextureCoordinate.

3.33 geometric sensor node

Geometric sensor nodes generate events based on user actions, such as a mouse click or navigating close to a particular object. A node of type ProximitySensor, VisibilitySensor, TouchSensor, CylinderSensor, PlaneSensor, or SphereSensor.

3.34 gravity

The force which causes masses to be attracted to one another. In the context of this standard, gravity may be simulated by constraining navigation to follow a surface. See "5.29 NavigationInfo" for details.

3.35 grouping node

Grouping nodes group child nodes and other grouping nodes together and cause the group to exhibit special behaviour which is dependent on the node type. A node of type Anchor, Billboard, Collision, Group, or Transform.

3.36 HSV

Hue, Saturation, and Value colour model.

3.37 HTML

Hyper Text Markup Language.

3.38 hyperlink

A reference to a URL which is associated with an Anchor node. See "5.2 Anchor" for details.

3.39 ideal VRML implementation

An implementation of VRML which presents all objects and simulates movement without approximation. Not realizable in practice.

3.40 IEC

International Electrotechnical Commission.

3.41 IETF

Internet Engineering Task Force. The organization which develops Internet standards.

3.42 image

A two dimensional rectangular array of pixel values. Pixel values may have from one to four components. See "6.5 SFImage" for details.

3.43 Internet

The worldwide network of interconnected computers which communicate with each other using a common set of communication protocols known as TCP/IP. The " Word Wide Web " is implemented on the Internet.

3.44 instance

An instantiation of a previously defined node created by the USE syntax.

3.45 interpolator node

Interpolator nodes define a piece-wise linear interpolation of a particular type of value at specified times. A node of type ColorInterpolator, CoordinateInterpolator, NormalInterpolator, OrientationInterpolator, PositionInterpolator, or ScalarInterpolator.

3.46 ISO

International Organization for Standardization

3.47 JPEG

Joint Photographic Experts Group.

3.48 JTC 1

Joint Technical Committee 1.

3.49 level of detail

The amount of detail or complexity which is displayed at any particular time for any particular object. The level of detail for an object is controllable as a function of the distance of the object from the viewer. See " 5. Node Reference- LOD " for details.

3.50 LOD

Level Of Detail.

3.51 loop

A sequence of events that results in an event being logically reponsible for generating itself. See "4.4.4 Loops" for details.

3.52 message

Strings sent between nodes upon the occurrence of events. See "4.5 Events" for details.

3.53 MIDI

Musical Instrument Digital Interface. A standard for digital music representation.

3.54 MIME

Multipurpose Internet Mail Extension. Used to specify filetyping rules for browsers. See "Concepts - File Extension and MIME Types" for details.

3.55 MPEG

Moving Picture Experts Group.

3.56 node

The fundamental component of a scene graph in VRML. Nodes are abstractions of various real-world objects and concepts. Examples include spheres, lights, and material descriptions. Nodes contain fields and events. Messages may be sent between nodes along routes.

3.57 node type

A required parameter for each node that describes, in general, its particular semantics. For example, Box, Group, Sound, and SpotLight. See "4.2 Nodes, Fields, and Events" and "5. Nodes Reference" for details.

3.58 object

A collection of data and procedures packaged according to the rules and syntax defined in this standard. "Object" is usually synonymous with "node".

3.59 PNG

Portable Network Graphics. A file format for images.

3.60 pointing device sensor

Pointing device sensor nodes generate events based on user actions, such as a mouse click or navigating close to a particular object. A node of type ProximitySensor, VisibilitySensor, TouchSensor, CylinderSensor, PlaneSensor, or SphereSensor.

3.61 polyline

A sequence of straight line segments joined end to end. A piecewise linear curve.

3.62 prototype

The definition of a new node type in terms of the nodes defined in this standard.

3.63 prototyping

A mechanism for extending the set of node types from within a VRML file.

3.64 public interface

The abstract definition of a node in this standard.

3.65 RGB

Red, Green, Blue colour model. This is the colour model used within VRML for the specification of colours. Each colour is represented as a combination of the three primary colours red, green, and blue.

3.66 route

The connection between a node generating an event and a node receiving an event.

3.67 RURL

Relative Uniform Resource Locator .

3.68 scene graph

An ordered collection of grouping nodes and leaf nodes. Grouping nodes, such as Transform, LOD, and Switch nodes, can have child nodes. These children can be other grouping nodes or leaf nodes, such as shapes, browser information nodes, lights, viewpoints, and sounds.

3.69 scripting

The process of creating a script.

3.70 simulation tick

The smallest unit capable of being identified in a digital simulation of analog time. VRML time is conceptually analog but is realized by an implementation as a digital simulation of the abstract analog time.

3.71 special group node

A node of type LOD (level of detail), InLine, or Switch. These nodes are grouping nodes which exhibit special behaviour. Examples of such special behaviour include selecting one of many children to be rendered based on a dynamically changing parameter value or dynamically loading children from an external file.

3.72 teleport

To move an avatar from one viewpoint to another.

3.73 texture coordinates

The set of 2D coordinates used by vertex-based geometry nodes (e.g., IndexedFaceSet and ElevationGrid) and specified in the TextureCoordinate node to map textures to the vertices of some geometry nodes. Texture coordinates range from 0 to 1 across the texture image.

3.74 time

A monotonically increasing value generated by TimeSensor nodes. Time (0.0) starts at 00:00:00 GMT January 1, 1970.

3.75 time sensor node

Time sensor nodes generate events at regular intervals in time. A node of type TimeSensor.

3.76 timestamp

The part of a message which describes the time the event occurred which caused the message to be sent.

3.77 URL

Uniform Resource Locator as defined in IETF RFC 1738.

3.78 URN

Uniform Resource Name.

3.79 UTF

UCS Transformation Format.

3.80 user

Person or agent who uses and interacts with VRML files by means of a browser.

3.81 VRML browser

See browser.

3.82 VRML document server

A computer program that locates and transmits VRML files and supporting files in response to requests from VRML client applications (browsers).

3.83 VRML file

A file containing information encoded according to ISO/IEC 14772.

3.84 world

A collection of VRML files and other multimedia content which, when interpreted by a VRML browser, presents an interactive experience to the user consistent with the author's intent.

3.85 world coordinate space

The coordinate system in which VRML worlds are defined is an orthogonal right-handed Cartesian coordinate system. The units of length are meters.

3.86 World Wide Web

The collection of documents and information linked together using the http Internet protocol.

3.87 XY plane

The plane perpendicular to the Z-axis which passes through the point Z = 0.0.

3.88 XZ plane

The plane perpendicular to the Y-axis which passes through the point Y = 0.0.

3.89 YZ plane

The plane perpendicular to the X-axis which passes through the point X = 0.0.