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GR2Advanced Computer

GraphicsAGR

GR2Advanced Computer

GraphicsAGR

Lecture 10VRML - An Introduction

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Good Ideas are SimpleGood Ideas are Simple

Realization 1:– Hypertext + Internet = World Wide Web

Realization 2:– Adding images makes pages more interesting

Realization 3:– Images are pictures taken by the publisher -

why not send 3D scenes and allow the user to take the picture!

VRML: Virtual Reality Modelling Language– a language to describe 3D worlds - for the

Web

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World Wide Web PagesWorld Wide Web Pages

AUTHORINGPROCESS HTML

file

server

INTERNET

client

WEBBROWSER

text/html

.htmlMIMEtype

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VRMLVRML

AUTHORINGPROCESS VRML

file

server

INTERNET

client

VRMLBROWSER

x-world/x-vrml

.wrl

Major browser:CosmoPlayer

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Advantages of VRMLAdvantages of VRML

Transferring a 3D model - rather than a 2D image - to the browser has great advantages– viewer can choose how to look at

the model - or world– viewer can navigate the world– file size can often be much less

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How Did It All Begin?How Did It All Begin?

Original brainwave– Mark Pesce and Tony Parisi - early 1994– vision of a VR interface to the Web

VRML 1.0– practical realisation based on Open

Inventor (Silicon Graphics toolkit - similar to OpenGL but higher level)

– Open Inventor file format PLUS hyperlinks

– static, non-interactive worlds– Gavin Bell (SGI) - late 1994

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Where are we now?Where are we now?

VRML97– adds object behaviours and

interaction to allow creation of dynamicdynamic worlds

– ISO standard - December 1997– Gavin Bell, Rikk Carey (ex-SGI) and

Chris Marrin (SGI) 2000

– being reworked as XML (X3D)– many new developments

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A VRML FileA VRML File

VRML file consists of:

header nodes

– objects such as cylinders and spheres

– operations such as transformations

fields– parameters of

nodes

#VRML V2.0 utf8Shape {

geometry Cylinder {

radius3height 6

}}

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As Seen By A BrowserAs Seen By A Browser

#VRML V2.0 utf8

Shape {

geometry Cylinder {

radius2

height 4

}

}

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Adding Colour to the Scene

Adding Colour to the Scene

#VRML V2.0 utf8

Shape {

geometry Cylinder {

radius 2

height 4

}

appearance Appearance {

material Material {

diffuseColor 1 0 0

specularColor 1 1 1 }

}

}

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Co-ordinate SystemsCo-ordinate Systems

Each node is drawn within its own local co-ordinate system..

x

z

y

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Modelling TransformationsModelling Transformations

...and can be subjected to a modelling transformation to scale, rotate, translate

Transform is a VRML node - treated just like an object

It applies to a group of children nodes

#VRML V2.0 utf8

Transform{

scale 5.0 0.5 1.0

children [

Shape {

geometry Cylinder {

radius 2

height 4

}

appearance Appearance {

material Material {

diffuseColor 1 0 0

specularColor 1 1 1 }

} } ] }

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Hierarchical StructureHierarchical Structure

#VRML V2.0 utf8

Transform{

scale 5.0 0.5 1.0

children [

Shape {

geometry Cylinder {

radius 2

height 4

}

appearance Appearance {

material Material {

diffuseColor 1 0 0

specularColor 1 1 1 }

} } ] }

TRANSFORM

SHAPE

parent

child

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Hierarchical StructureHierarchical Structure

This generalises to allow nodes to appear in a hierarchy

This is known as the VRML scene scene graphgraph

TRANSFORM

SHAPE TRANSFORM

SHAPE SHAPE

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TransformationsTransformations

Here we see Cylinder, Sphere and Cone nodes

Each has been subjected to a modelling transformation in order to position them

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InstancesInstances

A node can be given a ‘name’ and then used multiple times - with different transformations applied to each

DEF kwb Shape {...} gives it a name

USE kwb allows it to be included at other points in the scene graph

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AnchorsAnchors

A piece of geometry can act as a link to another URL

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TexturesTextures

Texture mapping: Images can be mapped to geometry to provide texturing

VRML looks like:Shape{

geometry Sphere { }

appearance Appearance{

texture ImageTexture{

url “http://..../kwb.gif”}

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Polygonal SurfacesPolygonal Surfaces

The general primitive for drawing polygonal surfaces is:– IndexedFaceSet– coord field lists

the points– coordIndex

describes the polygons

Shape{geometry IndexedFaceSet {

coord Coordinate {point [ 17.5 11.2 -

1.2,17.5 15.0 -

1.2,… ]}

coordIndex [ 0 1 2 3 -1,4 1 0 5 -1,…]

}}

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LightsLights

VRML includes:– DirectionalLight– PointLight– SpotLight

Note # sign is a comment

Example:

PointLight{

on TRUE

intensity 0.75

color 1 0 0 #red

location 0 0 0

radius 100

}

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Viewing Viewing

Specified via the Viewpoint node

VRML file can have a number of Viewpoint nodes - browsers allow a user to jump from one viewpoint to another

Orientation = axis + angle of rotation

Example:

Viewpoint {

position 0 0 5

orientation 0 0 1 0.3

description“frontview”

}

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Other Basic FeaturesOther Basic Features

Inline node– incorporate VRML code from

another url– this allows us to composecompose large

worlds from many smaller ones Level of Detail

– different geometric representations depending on distance

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Information About VRMLInformation About VRML

Web3D Consortium– http://www.web3d.org– links to specifications and resources

Web3D Information– http://web3d.about.com/compute/web3d

Leeds University VRML/Java3D Information Centre – http://www.scs.leeds.ac.uk/vrmljava3d

VRML Repository– http://www.sdsc.edu/vrml/

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Range of books now available– The VRML 2.0 Handbook (Addison Wesley)

Jed Hartman and Josie Wernecke

http://vrml.sgi.com/handbook– The Annotated VRML Reference Book (Addison

Wesley)

Rikk Carey and Gavin Bell

http://www.best.com/~rikk/Book/ Tutorials include:

– Floppy’s guide: www.vapourtech.com/vrmlguide

Books and TutorialsBooks and Tutorials