VRML 1

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Virtual Reality Modeling Language (VRML)

• Peter OGrady

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VRML

• Background
• Example VRML
• Versions
• VRML language
• Creating a VRML world

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VRML - Background

• Sometimes pronounced vermel.
• A language for building 3-D worlds on the WWW.
• Use a VRML browser to walk around virtual world.
• Browser downloads file containing description of
  world (in VRML format).
• Browser interprets scene descriptions and renders
  the resulting image.

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VRML - Background (2)

• Manipulation is performed on client (host)
  computer.
• Use of 3-D cards can speed performance.
• Rendering performed through lens of a virtual
  camera.
• Can move, twist and twirl.
• Can alter lighting.

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Using VRML
VRML Renderer usually browser plug-in or
ActiveX control
VRML text file .wrl
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VRML - History

• WWW conference in March 1994 - basic requirements
  defined.
• WWW conference October 1994 - draft specification
  of VRML 1.0 presented.
• Used language from a 3-D modeler
• Version 1.0 introduced April 1995.
• Version 97 now available and in use

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VRML Versions

• 1.0 Initial version. Static images.
• 97 aims to be multi-user, objects defined their
  behavior, participants can see each other

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VRML Language

• VRML 97 provides these extensions and
  enhancements to VRML 1.0
• Enhanced static worlds
• Interaction
• Animation
• Scripting
• Prototyping

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VRML Language

• Script-like language in ASCII text
• Given extension .wrl
• For easy identification of VRML files, every VRML
  97 file must begin with the characters
• VRML V2.0 utf8
• Scene graphs consist of nodes
• Each node has attributes
• See example on web site

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VRML Working Process

• Generation of a VRML file
• Transmission of VRML file to viewer
• Viewing of VRML world
• Interacting with the VRML world

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The Structure of VRML

• VRML can be viewed at a high level of abstraction
  as a collection of objects which are called
  nodes.
• These objects, or nodes, are defined for 3D
  graphics
• Nodes are arranged in hierarchical structures
  called scene graphs, which define an ordering for
  the nodes.

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The Structure of VRML

• This was originally based on the Open Inventor 3D
  toolkit developed by SGI, for VRML 1.0.
• The scene graph represents such aspects of a 3D
  world as geometry, materials, textures, geometric
  transformations, lights, viewpoints, and nesting
  structures.

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Characteristics of a Node

• A node might be a cube, a sphere, a texture map,
  a transformation, etc.
• The node has parameters that distinguish the node
  from other nodes of the same type.
• The node has a name.
• The node can be part of a hierarchy.

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Enhancement of VRML

• VRML 97 adds five constructs to VRML 1.0 that can
  significantly improve a 3D world.
• Four of these (namely node event field, routes,
  sensors, interpolators) connect and control
  animations, actions and reactions.
• The fifth (script nodes) allows for the interface
  with JavaScript or Java programs.

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Enhancement of VRML

• In addition, VRML 97 allows for video images (in
  MPEG format) to be mapped to a surface, collision
  detection, fog, text that always points to the
  user, contoured terrains, and texture mapped
  backgrounds.

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VRML Language -Nodes

• Cylinder
• bottom TRUE
• height 2
• radius 1
• side TRUE
• top TRUE

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VRML Language -Nodes

• Cone
• bottomRadius 1
• height 2
• side TRUE
• bottom TRUE

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VRML Language -Nodes

• Box
• size 2 2 2

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VRML Language -Nodes

• Sphere radius 1

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Coordinate Systems and Transformations

• VRML uses a Cartesian, right-handed,
  3-dimensional coordinate system.
• By default, objects are projected onto a
  2-dimensional display device by projecting them
  in the direction of the positive Z-axis, with the
  positive X-axis to the right and the positive
  Y-axis up.

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VRML Language -Nodes

• Transform
• children
• scale 1 1 1
• translation 0 0 0

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VRML Language -Nodes

• Coordinate
• point

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VRML Language -Nodes

• Color
• color

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VRML Language -Nodes

• PointSet color NULL coord
  NULL

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VRML Language -Nodes

• IndexedFaceSet
• color NULL
• coord NULL
• coordIndex
• normalIndex
• normalPerVertex TRUE
• solid TRUE

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VRML Language -Nodes

• Appearance
• material NULL
• texture NULL
• textureTransform NULL

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VRML Language

• Material - with attributes such as diffuseColor,
  and shininess
• diffuseColor 0 0 0 is black, 1 1 1 is white
• shininess 1.0 is highly reflective
• Translation - to specify position of object
• Level of Detail (LOD) nodes allow varying level
  of detail with distance
• WWWAnchor creates link to another VRML world

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Example 1 - source code
VRML V2.0 utf8 DEF Machine3 Transform
translation 2 0 0 rotation 0 1 0 0 children
Shape geometry Box size 6
10 6 appearance Appearance
material Material diffuseColor 0.2 0
0.8
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Example 2 - source code
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Example 2 - VRML World
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Creating VRML Worlds

• Free formed surfaces, such as that arising from
  imaging, are not included in the VRML
  specification.
• Therefore, a set of polygons should approximate
  to a free-formed surface or curve.

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Creating VRML Worlds

• For the purpose of rendering and shading the
  created polygons, their normal vectors are
  calculated and given to the respective polygons.
• Suppose that the surface is an imaging object.
  Then, the surface is translated into a VRML file
  format.

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Creating VRML Worlds - One Proposal
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Working With VRML

• Native code
• Converters
• Software that produces VRML code
• Can be large files - problem is to make the code
  efficient
• IIL work gives about 1001 reduction from
  original data set.

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Examples - See IIL Site

• Data from MRI
• Data from CT
• Lung
• Lung and tumor

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VRML and Medical Applications

• Visualization over WWW
• Need advanced methods to map from data to VRML.
• Acceleration
• 3D boards
• Better software

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Medical Applications - Creation of Virtual
Reality Worlds from Medical Imaging Data

• Image Segmentation
• VRML Mapping

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Literature on Medical Image Segmentation

• Manually
• Automatically
• Semi-automatically
• Thresholding
• Boundary finding
• Mathematical Morphology
• Region Growing

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Literature on Medical Image Segmentation

• Segmentation is a challenging task, especially
  considering an organ like the lung.
• Much of the work on lung segmentation has
  involved manual segmentation (Naidich et al,
  1993) but this involves considerable labor and
  can be prone to bias.

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Literature on Medical Image Segmentation

• Two Dimensional (2D) images require that the
  physician mentally determine 3D images from 2D
  slices, and this is difficult and error prone.
• The fundamental problems with current approaches
  to 3D display of scans are that they are not
  interactive once reported.

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Boundary Identification (2D Segmentation)

• Grouping Analysis
• Vx(Px,y,z) ABS((MEAN (Px-p,y,z ,. Px-2,y,z ,
  Px-1,y,z )-MEAN (Px1,y,z , Px2,y,z , Pxp,y,z
  ))

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Case Study - Lung/Tumor
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Case Study - Lung/Tumor
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Other Considerations

• Variety of VRML browsers available.
• Netscape uses Cosmo player (from SGI, CA) for
  VRML
• Microsoft new browser with IE 4
• For Windows 9x, Direct3D has been defined.
• 3D Boards now have Direct3D drivers
• Need to have VRML browser with Direct3D support.