VRML 1.0

In addition to the official VRML 1.0 specification there exists also a VRML 1.0 specification with clarifications and a VRML 1.0 specification with examples.

scene graph

A VRML-scene consists of a hierarchy (scene graph) of nodes. Each node defines a primitive shape, a property of appearance, a transformation, a lightsource, a camera, a WWW-link, a information or a group of other nodes.

state and local coordinate systems

Nodes change the state of the scene graph in the order they appear. Therefore a node affects the properties of the nodes that appear after it. For example a node whitch defines the current material to be red causes the following shapes to be drawn red. The change of state can be limited to affect only a part of the scene graph by using a separator node.

The current local coordinate system is also part of the state. A series of transformations

T1

...

Tn

pw=pl*Tn*...*T1

3spheres is an example with a material and two sequential transformations per sphere.

syntax of a node

A node of a predefined type is represented in the form

	type { fields children }

A Field is a specific parameter of that node, written in the form

	fieldname value

Children are other nodes contained in that node. Only grouping nodes may have children.

selfdefined nodetypes

The syntax for a new type of node is

	DEF newtype type { fields children }

Every other instance of this nodetype is created with

	USE newtype

To avoid that the instance created with the DEF is drawn you can use a switch, allowing you to use DEF/USE like functions without parameters.

	switch{
		DEF ...}

extensions

Extensions to VRML are supported by supporting self-describing nodes. This enables all VRML-implementations to parse (and to ignore) these extensions. A extended node-type is written in the form

	extendtype { fields[ fieldtype fieldname, ... ] fieldname fieldvalue ... }

If a extended node-type is a superset of an existing one it can be defined using isA

	extendtype { fields[ MFString isA, ...] isA["existtype"] ... }

These nodes represent primitive objects. Their parameters control specific properties like size or which parts are visible.

These nodes define a set of points, lines or faces by means of a list of points. Therefore they must be used together with a preceding Coordinate3 (look at Sierpinsky-Tetrahedron).

Defines a list of points in 3D-space. They are not visible unless used by a following IndexedFaceSet, IndexedLineSet or PointSet.

Sets the current font style for all following AsciiText-nodes.

They define the materials for all following shape-nodes. The different parts of a shape can consist of different materials. A material includes:

ambient color

diffuse color reflected from light sources

specular color and shininess for reflection-highlights (take a look at 3spheres)

emissive color for self-radiating objects (lightsources)

transparency (take a look at demo)

Theoretical VRML supports radiosity, but not all parameters must be used by a VRML-browser and thats why it is theoretical.

Defines a list of surface-normals and how they are bound to shapes. They are not visible unless used by a following IndexedFaceSet, IndexedLineSet or PointSet.

Shapes can be textured with a texture-map defined pixel per pixel in the VRML-file or as a picture (JPEG, GIF, PNG) read from an URL. A texture can be gray-scale (multiplied with material´s diffuse color) or color (replaces diffuse color) and with or without transparency. Lighting of textures depends on the implementation of the specific VRML-browser. The mapping of the texture on to the shape can be transformed. (look at demo). For an extended guide look at texture mapping in VRML 1.0.

Tells the VRML-browser if the following shapes are solid, convex or contain ordered vertices. This information can be used for rendering-optimizations.

These nodes transform the local coordinate system. Therefore they are used to set the position, rotation and distortion of all following shapes, lights and cameras (look at demo, 3spheres and Sierpinsky-Tetrahedron).

These nodes contain other nodes which makes the hierarchy of the scene graph possible.

Pushes the current state before traversing its children an pops it afterwards so that its children are isolated from the rest of the scene graph. In future versions of VRML all grouping nodes will behave this way to avoid side-effects.

Traverses a specific child or none, depending on the value of its whichChild-field. Can be used to DEFine nodetypes without displaying a corresponding node.

Selects one of its children depending on the distance (in local object- coordinates) to the eye-point. This allows different complex representations of an object depending how near the camera is.

Theoretical it allows recursive definitions of objects like L-systems (look at recursive Sierpinsky-Tetrahedron), but practical it results in a stack-overflow on some VRML-browsers (then you should better look at Sierpinsky-Tetrahedron with four levels of detail).

Defines its children to be a link to a corresponding WWW-document (URL). Usualy it is choosen by clicking on one of its children. It also consists of an information-string which can be displayed. If WWWAnchors are nested then the most deeply one is choosen.

Reads its children from an URL. The corresponding document should be a VRML-document otherwise results are undefined.

Defines the current camera. Only one camera should be traversed. Multiple cameras should be selected in a switch-node.

It shines from every position into the specified direction.

It shines from a specified point into every direction.

It illuminates in a specified cone from a specified point.

This node contains an information-string which is not displayed (for example: copyright).

don´t use this

These features will be removed in future versions of VRML, therefore they should not be used anymore

This is the basic grouping node which doesn´t push/pop the state. In future all grouping nodes will have to behave like Separator-nodes.

This grouping node pushes/pops only the transformation but not the rest of the state.

little practical value

general syntax

VRML is case-sensitive.

VRML-files have the extension .wrl (for world). Their MIME-type is x-world/x-vrml.

Every VRML 1.0-file must begin with this line:

	#VRML V1.0 ascii

A comment begins with a ´#´ (except for being a character in a string) and ends at the end of line. Comments and whitespaces may not be preserved. A VRML-document server may strip comments and extraneous whitespace from a VRML file before transmitting it. Blanks, tabs, newlines and carriage returns outside of string fields are whitespace characters.

Node names must not begin with a digit, and must not contain spaces or control characters, single or double quote characters, backslashes, curly braces, ´#´, ´+´ or ´.´.

Field names start with lower case letters, Node types start with upper case. The remainder of the characters must not be curly braces, square brackets, single or double quotes, ´#´, backslash, ´+´, ´.´ or ´&´.

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Heinrich Hey 1996