VRML - 1 Virtual Reality Modeling Language (VRML) Peter O’Grady

VRML - 2 VRML n Background n Example VRML n Versions n VRML language n Creating a VRML world

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

VRML - 4 VRML - Background (2) n Manipulation is performed on client (host) computer. n Use of 3-D cards can speed performance. n Rendering performed through lens of a virtual camera. n Can move, twist and twirl. n Can alter lighting.

VRML - 5 Using VRML VRML text file *.wrl VRML Renderer usually browser plug-in or ActiveX control

VRML - 6

VRML - 7

VRML - 8 VRML - History n WWW conference in March basic requirements defined. n WWW conference October draft specification of VRML 1.0 presented. n Used language from a 3-D modeler n Version 1.0 introduced April n Version 97 now available and in use

VRML - 9 VRML Versions n 1.0 Initial version. Static images. n 97 aims to be multi-user, objects defined their behavior, “participants” can see each other

VRML - 10 VRML Language n VRML 97 provides these extensions and enhancements to VRML 1.0: – Enhanced static worlds – Interaction – Animation – Scripting – Prototyping

VRML - 11 VRML Language n Script-like language in ASCII text n Given extension.wrl n For easy identification of VRML files, every VRML 97 file must begin with the characters: #VRML V2.0 utf8 n Scene graphs consist of “nodes” n Each node has attributes n See example on web site

VRML - 12 VRML Working Process n Generation of a VRML file n Transmission of VRML file to viewer n Viewing of VRML world n Interacting with the VRML world

VRML - 13 The Structure of VRML n VRML can be viewed at a high level of abstraction as a collection of objects which are called nodes. n These objects, or nodes, are defined for 3D graphics n Nodes are arranged in hierarchical structures called scene graphs, which define an ordering for the nodes.

VRML - 14 The Structure of VRML n This was originally based on the Open Inventor 3D toolkit developed by SGI, for VRML 1.0. n The scene graph represents such aspects of a 3D world as geometry, materials, textures, geometric transformations, lights, viewpoints, and nesting structures.

VRML - 15 Characteristics of a Node n A node might be a cube, a sphere, a texture map, a transformation, etc. n The node has parameters that distinguish the node from other nodes of the same type. n The node has a name. n The node can be part of a hierarchy.

VRML - 16 Enhancement of VRML n VRML 97 adds five constructs to VRML 1.0 that can significantly improve a 3D world. n Four of these (namely node event field, routes, sensors, interpolators) connect and control animations, actions and reactions. n The fifth (script nodes) allows for the interface with JavaScript or Java programs.

VRML - 17 Enhancement of VRML n 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.

VRML - 18 VRML Language -Nodes n Cylinder { bottom TRUE height 2 radius 1 side TRUE top TRUE }

VRML - 19 VRML Language -Nodes n Cone { bottomRadius 1 height 2 side TRUE bottom TRUE }

VRML - 20 VRML Language -Nodes n Box { size }

VRML - 21 VRML Language -Nodes n Sphere { radius 1 }

VRML - 22 Coordinate Systems and Transformations n VRML uses a Cartesian, right-handed, 3-dimensional coordinate system. n 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.

VRML - 23 VRML Language -Nodes n Transform { children [ ] scale translation }

VRML - 24 VRML Language -Nodes n Coordinate { point [ ] }

VRML - 25 VRML Language -Nodes n Color { color [ ] }

VRML - 26 VRML Language -Nodes n PointSet { color NULL coord NULL }

VRML - 27 VRML Language -Nodes n IndexedFaceSet { color NULL coord NULL coordIndex [ ] normalIndex [ ] normalPerVertex TRUE solid TRUE }

VRML - 28 VRML Language -Nodes n Appearance { material NULL texture NULL textureTransform NULL }

VRML - 29 VRML Language n Material - with attributes such as diffuseColor, and shininess n diffuseColor is black, is white n shininess 1.0 is highly reflective n Translation - to specify position of object n Level of Detail (LOD) nodes allow varying level of detail with distance n WWWAnchor creates link to another VRML world

VRML - 30 Example 1 - source code #VRML V2.0 utf8 DEF Machine3 Transform { translation rotation children [ Shape { geometry Box { size } appearance Appearance { material Material { diffuseColor }

VRML - 31 Example 2 - source code

VRML - 32 Example 2 - VRML World

VRML - 33 Creating VRML Worlds n Free formed surfaces, such as that arising from imaging, are not included in the VRML specification. n Therefore, a set of polygons should approximate to a free-formed surface or curve.

VRML - 34 Creating VRML Worlds n For the purpose of rendering and shading the created polygons, their normal vectors are calculated and given to the respective polygons. n Suppose that the surface is an imaging object. Then, the surface is translated into a VRML file format.

VRML - 35 Creating VRML Worlds - One Proposal

VRML - 36 Working With VRML n Native code n Converters n Software that produces VRML code n Can be large files - problem is to make the code efficient n IIL work gives about 100:1 reduction from original data set.

VRML - 37 Examples - See IIL SiteIIL Site n Data from MRI n Data from CT –Lung –Lung and tumor

VRML - 38 VRML and Medical Applications n Visualization over WWW n Need advanced methods to map from data to VRML. n Acceleration –3D boards –Better software

VRML - 39 Medical Applications - Creation of Virtual Reality Worlds from Medical Imaging Data n Image Segmentation n VRML Mapping

VRML - 40 Literature on Medical Image Segmentation n Manually n Automatically n Semi-automatically –Thresholding –Boundary finding –Mathematical Morphology –Region Growing

VRML - 41 Literature on Medical Image Segmentation n Segmentation is a challenging task, especially considering an organ like the lung. n 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.

VRML - 42 Literature on Medical Image Segmentation n Two Dimensional (2D) images require that the physician mentally determine 3D images from 2D slices, and this is difficult and error prone. n The fundamental problems with current approaches to 3D display of scans are that they are not interactive once reported.

VRML - 43 Boundary Identification (2D Segmentation) n Grouping Analysis n V x (P x,y,z ) = ABS((MEAN (P x-p,y,z,…. P x-2,y,z, P x-1,y,z )- MEAN (P x+1,y,z, P x+2,y,z, …P x+p,y,z ))

VRML - 44 Case Study - Lung/Tumor

VRML - 45 Case Study - Lung/Tumor

VRML - 46 Other Considerations n Variety of VRML browsers available. n Netscape uses Cosmo player (from SGI, CA) for VRML n Microsoft new browser with IE 4 n For Windows 9x, Direct3D has been defined. n 3D Boards now have Direct3D drivers n Need to have VRML browser with Direct3D support.