Virtual Reality Modeling Language (VRML97)

8/14/2019 Virtual Reality Modeling Language (VRML97)

1/31

Virtual Reality Modeling Language

(VRML97)

Anthony Steed 1998-2005


2/31

Introduction to VRML

s Virtual Reality Modelling Language

A file format to describe 3D scenes

identified by .wrl extension

Also a description of a run-time system foranimating worlds

Designed to be used in network situations

Supports interaction and simulation of behaviour

of objects Designed to run on desktop PCs through to high-

end workstations

MIME type is model/vrml


3/31

VRML Basics

s VRML file contains

Nodes that describe

the scene

s A Node is definedwith severalFields

Each line give the

field, the type of the

field, the name andthe default value.

s Example Node specification

Cone {

field SFFloat bottomRadius 1field SFFloat height 2

field SFBool side TRUE

field SFBool bottom TRUE

}


4/31

Sample VRML File example1.wrl

#VRML V2.0 utf8Transform {

children [

Shape {

appearance Appearance {material Material {

diffuseColor 0.1 0.7 0.2

}

}

geometry Sphere {

radius 2

} }

]

}

Every VRML97 file starts

#VRML V2.0 utf8


5/31

Classes of Node

s Shapes

Geometry

Appearance

s Transformations

s Lights

s

Groups


6/31

Shapes

s Each Shape has a geometry

field that contains a geometry

node and an appearance field

that contains an Appearance

node

Shape {

appearance

geometry

}

s Example (fromexample1.wrl)

Shape {

appearance Appearance {material Material {


}

}

geometry Sphere {radius 2

}


7/31

Geometry Nodes

s Basic types

Box

Sphere

Cylinder Cone

Text

s Box

defined by its size field

Box {

size 2.0 2.0 2.0

}

s Sphere

defined by its radius field

Sphere {

radius 1.5}


8/31

Geometry Nodes

s Cylinder

defined by its height and

radius fields

Cylinder {

height 2.0radius 1.0

}

s Cone

defined by its height and

radius fieldsCone {

radius 1.3

height 1.8

}

s Text

defined by the string

and the font

geometry Text {string ["Hi!"]

fontStyle FontStyle {

family "TYPEWRITER"

style "ITALIC"

}

}


9/31

Complex Geometry

s Many objects can not be described with

standard solids

s

General geometry described with IndexedFaceSet, IndexedLineSet,PointSet, ElevationGrid, Extrusion

s Each uses some of the following nodes

in definition Coordinate, Normal, Color,

TextureCoordinate


10/31

PointSet

s Define a set of points and the colour of

each point

10

11


11/31


12/31

IndexedFaceSet

s Components

the points to construct the face from

the normals to give at the points

the colours of the points

the texture coordinates of the points

s Can define normals and colours

for each vertex or each face

s Texture coordinate defined at each vertex Hints

each face is convex the faces are defined in counter-clockwise order

the object is solid (i.e. each triangle is one-sided)


13/31

IndexedFaceSet

s Coordinate

s Define faces using list of vertices each

terminated by -1

geometry IndexedFaceSet {coord USE COORDS

coordIndex [ 0, 2, 9, 5, 0, -1, 3, 0, 5, 11, 3, -1,

1, 3, 11, 7, 1, -1, 2, 1, 7, 9, 2, -1

0, 3, 10 ,4, 0, -1, 3, 1, 6, 10, 3, -1,2, 8, 6, 1, 2, -1, 2, 0, 4, 8, 2, -1,

9, 8, 4, 5, 9, -1, 5, 4, 10, 11, 5, -1,

11, 10, 6, 7, 11, -1, 7, 6, 8, 9, 7, -1

]


14/31

IndexedFaceSet

s Colour per facecolor Color { color [ 1 1 1, 0.3 0.3

0.3]}

colorPerVertex FALSE

colorIndex [ 0, 0, 0, 0, 0, 0,0, 0, 1, 1, 1, 1]

s Colour per vertexcolor Color { color [ 1 1 1, 0.3

0.3 0.3]}

colorPerVertex TRUE

colorIndex[ 0, 1, 1, 0, 0, -1, 1, 0, 0, 1, 1,

-1,

0, 1, 1, 0, 0, -1, 1, 0, 0, 1, 1, -1

0, 1, 1 ,0, 0, -1, 1, 0, 0, 1, 1, -1,

0, 1, 1 ,0, 0, -1, 1, 0, 0, 1, 1, -1,

0, 1, 1 ,0, 0, -1, 1, 0, 0, 1, 1, -1,

0, 1, 1 ,0, 0, -1, 1, 0, 0, 1, 1, -1

]12 colours = 1 per face 72 indices = 1 for each vertex in the

face set definition


15/31

IndexedFaceSet

s Normal defines the direction of

each point and the way it

reflects light

default normal isperpendicular to surface

of polygon

polygon is flat if all

normals point same way

otherwise smoothinterpolation

normal Normal {

vector [

-1 0 -1, 1 0 1, 1 0 -1, -1 0 1,

1 0 0, -1 0 0, 0 0 1, 0 0 -1

]

}

normalPerVertex TRUE

normalIndex [5, 7, 7, 5, 5, -1, 6, 5, 5, 6, 6, -1,

4, 6, 6, 4, 4, -1, 7, 4, 4, 7, 7, -1

5, 6, 6 ,5, 5, -1, 6, 4, 4, 6, 6, -1,

7, 7, 4, 4, 7, -1, 7, 5, 5, 7, 7, -1,

1, 1, 1, 1, 1, -1, 2, 2, 2 ,2, 2, -1,

0, 0, 0, 0, 0, -1, 3, 3, 3, 3, 3, -1

]


16/31


17/31

IndexedLineSet

s Defines a line set

s Colour per line or per vertexgeometry IndexedLineSet {

coord USE COORDS

coordIndex [ 0, 4, 5, 0, -1, 3, 10 , 11, 3, -1,

1, 6, 7, 1, -1, 2, 8, 9, 2, -1,

0, 2, 1, 3, 0, -1,

4, 8, 6, 10, 4, -1,

5, 9, 7, 11, 5, -1]

color Color { color 1 1 1}colorPerVertex FALSE

colorIndex [ 0, 0, 0, 0, 0, 0, 0, 0,

0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]

}


18/31

Transformations

s Define the positions of objects in 3Dspace

s XY are the plane of the screens

Z is towards the Viewers Transformation basically contains

rotation

scale

translation a set of children nodes

s Rotations follow right-hand screwrule

X

Z

Y


19/31

Effects of Transformation

s translationTransform {

translation 1 1 -1

children [

]}

s rotationtranslation 1 1 -1

rotation 0 1 0 0.785

s

scaletranslation 1 1 -1rotation 0 1 0 0.785

scale 0.5 1.0 0.5


20/31

Scene Graph

s Transforms are

hierarchical

forms a directed

acyclic graph

Transform {

translation 0 2 0

children [

Shape { }

Transform {

translation 2 0 0

children [

Shape { }

Transform {

translation 0 0 -2

children [

Shape { }

]

}

]

}

]

}


21/31


22/31

Node Re-Use

s Objects can be re-usedusing DEF/USE pairs

s DEF a name for a nodewhen it is first being

decsribedUSE a node

whenever a node of thattype is required I.E. if you DEF an

Appearance node thenUSE of that node mustbe in a place that is validfor an Appearance nodeto be

DEF UCL_BOX Shape {

appearance Appearance {

texture ImageTexture {

url ["logo.jpeg"]

}

}

geometry Box {

size 2 2 2

}

}


23/31

DEF/USE Example

#VRML V2.0 utf8

Transform {

translation 0 0 0

children [

DEF UCL_BOX Shape {

appearance Appearance {

texture ImageTexture {

url ["logo.jpeg"]}

}

geometry Box {

size 2 2 2

}

}

]

}

Transform {

translation 0 3 0

children [

USE UCL_BOX

]

}


24/31

Appearance

s Defines the look of some piece of geometry Material

combination of ambient colour, diffuse colour, emmisive colour,shinines,

transparency, specular colour Texture

defines a picture to paste to the object fetch from a URL

supports movies

TextureTransform defines how the picture is applied to the object


25/31

Material Examples

s Material Shiny Material

ambientIntensity 0.3


specularColor 0.6 0.8 0.6

shininess 0.6 Dull Material

ambientIntensity 0.1


shininess 0.0

Transparent Material diffuseColor 0.1 0.7 0.2

transparency 0.5

Colour components defined inRGB (red, green, blue triplets)


26/31

Lights

s Provide illumination in the scene

DirectionalLight

PointLight

SpotLights DirectionalLight

light rays travelling in parallel lines e.g. sunlightDirectionalLight {

direction -1 -1 -1

intensity 0.8

}


27/31

Lights

s PointLight

radiate in all directions

s SpotLight

radiate only in certain directions, and with

volumes of different intensity

s SpotLight and PointLight attenuate -

their effect can decrease over distance


28/31

Other Things

s Interaction

s Scripting

Java

JavaScripts Interpolators

s Sensors

s Fog

s Background

s Audio

s Video

s LOD

s Billboard


29/31

LOD

s Switches between two ormore views depending ondistance

s

Nearby ViewBunny1 = ~56K polygons

s Distant View

Bunny2= ~1K polygons


30/31

Billboards

s Billboards object always faces the

viewer

Transform {

translation 0 3 0

children [

Billboard {

children [

USE UCL_BOX

]

}

]

}


31/31

Summary

s VRML97 provides a simply file format to

put 3D objects on the web

sAnimation and scripting are allowed, but

we havent discussed these

s Somewhat restricted model of local

lighting compared to todays graphics

cards

Documents

Virtual Reality Modeling Language (VRML97)