GR2 Advanced Computer Graphics AGR

1. GR2Advanced Computer GraphicsAGR Lecture 11 VRML Animation and Interaction

2. We have seen how to build hyperlinked, static, non-interactive 3D worlds VRML - The Story So Far #VRML V2.0 utf8 Shape { geometry Cylinder { radius 2 height 4 } appearance Appearance { material Material { diffuseColor 1 0 0 specularColor 1 1 1 } } }

3. Richer Worlds • VRML97 allows the creation of much more interesting worlds by introducing: • interaction and animation • multimedia • scripting • Worlds become active • can change over time • can change in response to a user’s actions

4. Making Worlds Come Alive • To understand how this works we shall create a really simple example • We shall build a signboard that rotates ... • ... for this we need to understand events and sensors

5. Sensors and Events • A sensor is a type of node that generates data within the world - as the browser navigates it • eg TimeSensor • eg TouchSensor • Data generated within a node is called an event • Events are routed from one node to another to program behaviour in the world

6. Routing of Events • Each node has a specified list of events associated with it • eg TimeSensor has time events • Divided into eventOuts and eventIns • a node can receive eventIns • a node can send eventOuts • Routes assign eventOut of one node to eventIn of another node route Node A Node B eventOuts eventIns

7. Example of Routing DEF OBJECT Shape { .. } DEF LIGHT PointLight { .. } DEF TIMER TimeSensor { .. } DEF SWITCH TouchSensor { .. } # start the clock when someone presses dimmer switch ROUTE SWITCH.touchTime TO TIMER.set_startTime # as the clock ticks, change the intensity of light in the room ROUTE TIMER.fraction_changed TO LIGHT.set_intensity

8. Time Sensor • A Time Sensor generates events as the clock ticks • Fields include: • start time (secs) [0 is default = midnight, 1/1/1970] • cycle time (secs) [1 is default] • loop (TRUE/FALSE) • EventOuts include: • current time • fraction_changed (fraction of current cycle) • EventIn includes • set_startTime

9. Animation • Animation is achieved by routing time events to an animation engine • This engine is programmed with keyframe values • on receiving a time event, it calculates an ‘in-between’ value • this gets routed to another node, typically a transform node

10. Interpolator Nodes • These form the animation engines • Example is Orientation Interpolator OrientationInterpolator { key [0, 0.5, 1] keyValue [0 1 0 0, 0 1 0 3.14, 0 1 0 6.28] } • EventIn set_fraction (eg 0.25) • EventOut value_changed (eg 0 1 0 1.57) Note: Orientation specified as angle about axis - here y-axis

11. Animation • Animation then achieved by routing time events from a time sensor to the animation engine... • ... which then drives say a transform node: animation engine modify geometry sensor ROTATIONINTERPOL- ATOR TRANSFORM TIME SENSOR time elapsed rotation event event

12. Rotating Sign DEF TURN_SIGN Transform { rotation 0 1 0 0 children [ DEF SIGN Shape {...} ] } DEF TIMER TimeSensor { loop TRUE } #continuous DEF ROTOR OrientationInterpolator { key [0, 0.5 1.0] keyValue [0 1 0 0, 0 1 0 3.14 0 1 0 6.28] #rotate twopi in a cycle } ROUTE TIMER.fraction_changed TO ROTOR.set_fraction ROUTE ROTOR.value_changed TO TURN_SIGN.set_rotation

13. User Activated Sensors • Another set of sensor nodes generate events in response to user actions • A TouchSensor node creates an event when you click on any sibling geometry nodes • siblings are brothers / sisters (ie at same level in hierarchy) • an eventOut called “touchTime” is created

14. Touch Sensor Example DEF TURN_SIGN Transform { rotation 0 1 0 0 children [ DEF SIGN Shape {...} DEF HIT TouchSensor{ } ] } DEF TIMER TimeSensor { loop FALSE } #once only DEF ROTOR OrientationInterpolator { key [0, 0.5, 1.0] keyValue [0 1 0 0, 0 1 0 3.14 0 1 0 6.28] #rotate twopi in a cycle } ROUTE HIT.touchTime TO TIMER.set_startTime ROUTE TIMER.fraction_changed TO ROTOR.set_fraction ROUTE ROTOR.value_changed TO TURN_SIGN.set_rotation

15. Proximity Sensor • This acts as a detector as the viewer enters a region • It generates events on entry and exit • You can use this for example to turn on a light as someone enters a room

16. Proximity Sensor Example DEF SIGN Shape {...} DEF TIMER TimeSensor { loop FALSE } #once only DEF SPY ProximitySensor { size 16 16 16 } DEF LIGHT PointLight { intensity 0 location 0 0 5} NavigationInfo { headlight FALSE } # turn off the browser h’light # start clock when browser nears the sign ROUTE SPY.enterTime TO TIMER.set_startTime # increase the intensity from zero to one in the time cycle ROUTE TIMER.fraction_changed TO LIGHT.set_intensity

17. Other Sensors • Drag sensors • PlaneSensor • CylinderSensor • SphereSensor these constrain the allowable motion

18. Collision Detection • VRML allows you to detect when the viewer collides with an object • Collision { children [ ...] } • When collision occurs, a ‘collideTime’ event is generated • Note collision between objects NOT detected

19. Sound location full intensity • Sound node • location and direction fields specify where the sound emanates from • source field specifies an AudioClip node... which points at a .wav file given as a url * sound fades

20. Collision + Sound Example DEF COLLIDE Collision { children [ DEF SIGN Shape { .. } ] DEF TUNE Sound { source DEF CLASSIC AudioClip { url "http://.....wav"} } ROUTE COLLIDE.collideTime TO CLASSIC.set_startTime

21. Movies • Textures can be movies rather than static images • Use the MovieTexture node...

22. User Control of VRML Worlds • There are two mechanisms for allowing user control of VRML worlds - scripts and external authoring • Both involve the execution of Java software in association with the VRML world • Java of course is a programming language allowing portable code to be delivered to the browser for execution • scripts: Java or JavaScript inside VRML • external authoring: Java and JavaScript outside VRML

23. VIEWPOINT SCRIPT NODE TIME SENSOR java code time elapsed position Scripting • Script node • allows a world creator to program their own animation engine • url field points to Java or JavaScript code • events can be routed to and from script nodes • example: viewpoint animation

24. Example of Scripting • In the following example, the heights on an elevation grid are animated using a script node • ElevationGrid node draws surface through heights defined on a grid Colours can be assigned to each vertex and smoothly interpolated

25. Example of Scripting - Dynamic Change of Surface Shape{ geometry DEF GRID ElevationGrid{ height [ ... ] } appearance ... } DEF TIMER TimeSensor { loop TRUE } DEF ENGINE Script { eventIn SFFloat time_fraction eventOut MFFloat new_height url:javascript <JavaScript code goes here, to create new set of heights at grid points, based on time> } ROUTE TIMER.fraction_changed TO ENGINE.time_fraction ROUTE ENGINE.new_colour TO GRID.set_height

26. Script node allows Java code to be included within a VRML world External Authoring Interface (EAI) allows a Java applet to link to a VRML world Linking Software to VRML Worlds Java applet script node VRML node VRML node VRML world VRML world

27. Allows communication between a Java applet and a VRML world.. Here is a virtual shopping mall.. External Authoring Interface Clicking on a TouchSensor over an object sends event to Java applet which keeps record of purchases

28. Has been a range of browsers to select from Commonly: free beta Not all browsers support all functionality... Rapidly changing environment Leading product is CosmoPlayer developed by SGI spun-off to Cosmo sold to Platinum yesterday (sic) agreed to be Open Source Other players: Sony (CommunityPlace) Browsing

29. Authoring • Variety of approaches: • use a text editor • use an interactive modeller • Cosmo Worlds (SGI - Cosmo- Platinum-??) • Caligari truespace3 • use a higher level language to author, then interpret • generate dynamically from software • generate automatically from scanner

30. Futures • Development being controlled by VRML Consortium (http://www.vrml.org) • Plans underway to develop X3D - or VRML2000 • Interesting areas for research • 3D user interfaces • large worlds • multi-user worlds • integration of VRML and MPEG • 4D navigation • Eye on web site: http://www.scs.leeds.ac.uk/vrmljava3d