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Event Routing

Event Routing. Some VRML nodes generate events in response to environmental changes or user interaction. Event routing gives authors a mechanism, separate from the scene graph hierarchy, through which these events can be propagated to effect changes in other nodes.

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Event Routing

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  1. Event Routing • Some VRML nodes generate events in response to environmental changes or user interaction. Event routing gives authors a mechanism, separate from the scene graph hierarchy, through which these events can be propagated to effect changes in other nodes. • Once generated, events are sent to their routed destinations in time order and processed by the receiving node. This processing can change the state of the node, generate additional events, or change the structure of the scene graph. • Script nodes allow arbitrary, author-defined event processing. An event received by a Script node causes the execution of a script function which has the ability to send events through the normal event-routing mechanism. • The ideal event model processes all events instantaneously in the order that they are generated. • A timestamp, the time at which an event is delivered to a node, serves two purposes. First, it is a conceptual device used to describe the chronological flow of the event mechanism. It ensures that deterministic results can be achieved by real-world implementations which must address processing delays and asynchronous interaction with external devices. Second, timestamps are also made available to Script nodes to allow events to be processed based on the order of user actions or the elapsed time between events.

  2. Events & Routes (Interacting with the Scene) • A class of nodes, called sensors reacts to user events in some prescribed ways. • TouchSensor, ProximitySensor • a sensor is wired to a Script node that runs a program TouchSensor Node Sound Node Rout eventOut eventIn

  3. #VRML V2.0 utf8 #Event routing Group { children [ Shape { appearance Appearance { material Material { } } geometry Cone { } } DEF TS TouchSensor { } # define the sensor "TS" DEF DL DirectionalLight { # define the light "DL" color 1 0 0 on FALSE } ] ROUTE TS.isOver TO DL.set_on }

  4. Animation and User Interaction • The translation field of the Transformation node is an exposedfield • set_:incoming event • set_translation • _changed:outgoing event • translation_changed • ROUTE Xform1.translation_changed TO Xform2.set_translation • ROUTE Xform1.translation TO Xform2.translation

  5. ROUTE • Routing should be done in same type (field) • a set_ or _changed event is the same type as the exposed field it’s associated with • use DEF & USE Group { children [ DEF LIGHT_CONTROL TouchSensor {} Inline { url [“lightswitch.wrl]}]} DEF Light PointLight { location -6 4 2 on FALSE} Inline {url [“table.wrl”]} ROUTE LIGHT_CONTROL.isActive TO Light.on

  6. The Animation Event Path Trigger • Trigger : generates an event. Usually sensors • Logic : processing on the event. Usually script nodes • Timer : startTime of TimeSensor node, then generates time events • Engine : route time events to nodes that animate. Usually interpolator node Logic Timer Engine Target

  7. The Animation Event Path Trigger • Target : The browser sends the Engine’s output to a relevant node in the scene hierarchy, whoses field values changes accordingly Logic Timer Engine Target Trigger Target

  8. Pointing-device Sensors • The geometry corresponding to a sensor must be a sibling of the sensor • The objects controlled by the sensor can be anywhere • TouchSensor • isOver • isActive (on click) • isActive + hitPoint_changed (on drop) • touchTime (press remaining on same object)

  9. Using a TouchSensor node Group { children [ DEF PUSH TouchSensor {} Inline { url [“doorbell.geom.wrl”]}]} Sound { source DEF BUSS AudioClip {url [“doorbell.wav”]} maxFront 50 minFront 5} ROUTE PUSH.touchTime TO BUZZ.startTime • Trigger sends a time event to the Target (the audio clip)

  10. Drag Sensors • Interpretation of 2D dragging • CylinderSensor : rotating around local y axis • spinning a globe • PlaneSensor : translating in the local xy plane #VRML V2.0 utf8 GROUP { children [ DEF SKULL_DRAG PlaneSensor { minPosition 0 0 maxPosition 5 0 } DEF SKULL Transform { translation 0 0 0 children [ Inline {url [“skull.wrl”]}]}]} ROUTE SKULL_DRAG.translation_changed TO SKULL.translation

  11. ProximitySensor • Generates events whenever the user enters or leaves a defined box-shaped region • Sizes for box shapes can be difficult to estimate --> so, placing a Box node of the same size at the same location will give a good idea of the exact region

  12. Timers Trigger Logic Timer Engine Target • Time Sensor is triggered/initiated by setting startTime • cycleInterval sets the interval of animation • fraction_changed is used to calculate time elapse among the given interval Viewpoint { position 0 0 15} DEF DETECTOR ProximitySensor {size 25 25 25} DEF TIMER TimeSensor {cycleInterval 2} DEF LIGHT PointLight { intensity 0 location 3 3 3} Inline {url [“chacmool.wrl”]} #objects to be lit ROUTE DETECTOR.enterTime TO TIMER.startTime ROUTE TIME.fraction_changed TO LIGHT.intensity

  13. Engines Trigger Logic Timer Engine Target • Convert the output of a time sensor into a change in some other type of value • interpolator & keyframe • PositionInterpolator • OrientationInterpolator • ColorInterpolator • ScalarInterpolator • CoordinateInterpolator DEF Spark_mover PositionInterpolator { key [0,1] keyvalue [0 0 0, 0.8, 5,0]} ROUTE TIME.fraction_changed TO Spark_mover.set_fraction ROUTE Spark_mover.value_changed TO Spark.translation

  14. Example (bike rider - bike.wrl) #VRML V2.0 utf8 DEF BIKE Transform { translation 0 0 0 children [ DEF FW Transform { translation -2 -4 0 children [ Inline { url "wheel2.wrl"}]} DEF BW Transform { translation 2 -4 0 children [ Inline { url "wheel2.wrl"}]} DEF FR Transform { translation 0.4 -3.5 2.1 children [ Inline { url "frame.wrl"}] } ]} DEF RIDER Transform { translation 0 0 0 children [ Inline { url "rider2.wrl"}]} DEF T TimeSensor { loop TRUE enabled TRUE cycleInterval 5 stopTime -1} DEF P PositionInterpolator { key [ 0, 0.25, 0.5, 0.75, 1] keyValue [ -5 0 0, -1 0 0, 0 3 0, 2 0 0, 5 0 0]} ROUTE T.fraction_changed TO P.set_fraction ROUTE P.value_changed TO BIKE.translation ROUTE BIKE.translation TO RIDER.translation

  15. More examples • rider.wrl • frame.wrl • wheel.wrl

  16. Scripting (Script node) • Bridge between VRML & programming languages. • Acting as the Engine stage to control animation • Processing input to act as the Logic stage • Interacting with the browser in certain ways • binding the browser to a Viewpoint node to animate the viewer along a path • Manipulating the scene hierarchy • communicating with a server or another VRML world across a network

  17. What to know about Scripting • How the script node acts as a bridge between VRML & JAVA • Basic JAVA classes that interact with and manipulate VRML • How to compile and run java program

  18. The script node act as a gateway to the script itself Script node Scene url A node eventin translation eventOut rotation another node size translation color rotation JAVA code size color

  19. Example (ChangeColor.wrl) #VRML V2.0 utf8 Transform { children [ DEF TS TouchSensor {} # TouchSensor Shape { appearance Appearance { material DEF SphereColor Material { diffuseColor 1 0 0 } # red } geometry Sphere {} } ] } DEF ColorScript Script { url "ChangeColor.class" eventIn SFBool clicked eventOut SFColor newColor field SFBool on FALSE } # Routing ROUTE TS.isActive TO ColorScript.clicked ROUTE ColorScript.newColor TO SphereColor.set_diffuseColor

  20. Example (ChangeColor.java) import vrml.*; import vrml.field.*; import vrml.node.*; public class ChangeColor extends Script { private SFBool on; // status of on-off float red[] = { 1, 0, 0 }; // RGB(Red) float blue[] = { 0, 0, 1 }; // RGB(Blue) private SFColor newColor ; public void initialize() { newColor = (SFColor) getEventOut("newColor"); on = (SFBool) getField("on"); } public void processEvent(Event e) { ConstSFBool v = (ConstSFBool)e.getValue(); if(v.getValue()){ if (on.getValue()) { newColor.setValue(red); // set red to 'newColor' } else { newColor.setValue(blue); // set blue to 'newColor' } on.setValue(!on.getValue()); // = !on.getValue(); } } }

  21. Example II (mover.wrl) #VRML V2.0 utf8 DEF MOVER Transform { translation 0 0 10 children [ DEF TS TouchSensor {} # TouchSensor Shape { appearance Appearance { material DEF SphereColor Material { diffuseColor 1 0 0 } # red } geometry Sphere {} } ]} DEF MoveIt Script { url "MoveIt.class" eventIn SFBool clicked field SFNode node USE MOVER field SFBool on FALSE } # Routing ROUTE TS.isActive TO MoveIt.clicked

  22. Example II (moveit.java) import vrml.*; import vrml.field.*; import vrml.node.*; public class MoveIt extends Script { private SFBool on; // status of on-off float red[] = { 1, 0, 0 }; // RGB(Red) float blue[] = { 0, 0, 1 }; // RGB(Blue) private SFNode theNode ; private SFVec3f position; public void initialize() { theNode = (SFNode) getField("node"); } public void processEvent(Event e) { ConstSFBool v = (ConstSFBool)e.getValue(); Node node; if(v.getValue()){ node = (Node)(theNode.getValue()); position = (SFVec3f)(node.getExposedField("translation")); position.setValue((position.getX() + 5), 0, 0); } } }

  23. JAVA & The script node • getSize() • getValue() • get1Value(int index) • setValue(value) • set1Value(int index, value) • addValue(value) • insertValue(int index, value) • deleteValue(int index) • clearValue()

  24. Compiling a JAVA script • Download vrml package (vrml.*) • put it in a directory where your classpath can reach

  25. Project 1 • Your first project is (1) to make you feel comfortable with VRML world. Build your (static) VRML world. You may import 3D models from other tool, but you should have full control over the model to make use of them in your project 2. This project is also (2) to make your base environment for project 2 (multi user game). Therefore, think carefully in advance, not to waste your time and do it again for project 2. Your project 2 should have some component that multi users interact in 3D world. For example, car racing game needs cars and tracks at least. Shooting game needs 3D avatars and shooting environment. You build at least a car and tracks that you want to use for racing game. For project 1, your world can be static, no need to animate, respond to user input, nor events handling. Build your static world in .wrl file and test in your browser. For project 2, you will have to work towards installing (or implementing) server, EAI scripting of your VRML components using java (this also requires game algorithm – collision, running speed, etc).

  26. Grading : Grading of project I will be based on your world and documentation. Your world needs to have textured and navigatable environment, with multiple light sources. If your world looks reasonable enough for project 2, then you will get most of credit. For documentation, draw scene graph at least. Also use this documentation as a proposal for your project 2 since you will have to spend some time to design project 2 anyway. • Submission : Hard copy of documentation that obviously includes URL of your world by 4:00 pm of 10/8/2001.

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