Virtual Reality Modeling Language 97 Whats VRML Virtual

Virtual Reality Modeling Language 97

What’s VRML? • Virtual Reality Modeling Language 2 D/3 D graphics Audio: . wav, . mid Video: MPEG-1 Interactivity: time- and action-based Hyperlinks Java • VRML 97 International Standard (IS) ISO/IEC 14772 -1: 1997

Basic Concepts • VRML File Structure Prototypes Scene Graph Event Routing • A VRML browser

VRML File Structure • A VRML file contains #VRML V 2. 0 utf 8 # A sample VRML 97 file Prototypes Scene graph Event routing

Prototypes • Provides a capability to extend VRML node types • Can reuse defined nodes – e. g. , defines different chairs, tables, etc.

Scene Graph • A hierarchical structures for nodes • Good for transformations • Good for event generation and routing

Event Routing • For interactivity • User, time, or script triggered • Routing path defined by authors – e. g. , collide --> alarm --> crash -->. . .

A VRML Browser user input VRML file Parser built-in nodes prototypes World scene graph routing path Audio/Visual Presentation user

Node Reference (1) Group Nodes (2) Coordinates (3) Anchor (4) Sound (5) Sensor (6) Interpolator (7) Script

Group Nodes • Transformations, events, etc. occur within a group • Includes: • Group: all children • Transform: all children, new coordinate • Switch: one child Group { children [ Shape { … }. . . ] }

Coordinates Transform { # X Y Z translation 2. 0 0. 0 children [ Shape Cylinder { radius 1. 0 height 1. 0 }, ] }

Anchor • A group node • Select any child in the group jumps to a new VRML file Anchor { url "stairway. wrl" } description "Floating Stairs" children [. . . ] }

Sound • Audio. Clip: signal source • Sound: place to play Sound { source Audio. Clip { url "bach. wav" description ”music" loop TRUE start. Time 1 stop. Time 0 }, location 0 0 0 min. Front 10 min. Back 10 max. Front 40 max. Back 40 spatialize TRUE },

Sensor • Generated from depressed buttons, collision, timer, etc. • Define a route path to trigger other nodes • Each node has event. In and event. Out interfaces out A B in

Interpolator Position. Interpolator { key [ 0. 0, 0. 5, 1. 0 ] key. Value [ 0. 0, 3. 0 0. 0, 0. 0 ] } • Given a fraction [0. . 1], interpolate a new value – e. g. , given 0. 3 --> key = 0. 3 --> key. Value = (0. 0+3. 0)/0. 5*0. 3 = 1. 8, i. e. , (1. 8, 0. 0)

Script • Extend VRML’s capabilities to more complex objects/behaviors Script { field … event. In …set_zzz event. Out … xxx_changed url "circle. class" or. . . url "circle. js" or. . . url "javascript: . . . " }

References • Official site: www. vrml. org • VRML repository: www. sdsc. edu/vrml • Industry: – vrml. sgi. com – www. intervista. com – www. microsoft. com/vrml