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.

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

NodeeventOut

eventIn

Rout

#VRML V2.0 utf8#Event routingGroup { 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 0on FALSE

} ]ROUTE TS.isOver TO DL.set_on}

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

ROUTERouting should be done in same type (field)a set_ or _changed event is the same type as

the exposed field it’s associated withuse DEF & USEGroup {

children [ DEF LIGHT_CONTROL TouchSensor {} Inline { url [“lightswitch.wrl]}]}

DEF Light PointLight {location -6 4 2on FALSE}

Inline {url [“table.wrl”]}ROUTE LIGHT_CONTROL.isActive TO Light.on

The Animation Event Path

Trigger : generates an event. Usually sensorsLogic : processing on the event. Usually script

nodesTimer : startTime of TimeSensor node, then

generates time eventsEngine : route time events to nodes that animate.

Usually interpolator node

Trigger Logic Timer Engine Target

The Animation Event Path

Target : The browser sends the Engine’s output to a relevant node in the scene hierarchy, whose field values changes accordingly

Trigger Logic Timer Engine Target

Trigger Target

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)

Using a TouchSensor node

Trigger sends a time event to the Target (the audio clip)

Group {children [ DEF PUSH TouchSensor {} Inline { url [“doorbell.geom.wrl”]}]}

Sound {source DEF BUSS AudioClip {url [“doorbell.wav”]}maxFront 50minFront 5}

ROUTE PUSH.touchTime TO BUZZ.startTime

Drag SensorsInterpretation of 2D dragging

CylinderSensor : rotating around local y axis• spinning a globe

PlaneSensor : translating in the local xy plane

#VRML V2.0 utf8GROUP { children [

DEF SKULL_DRAG PlaneSensor {minPosition 0 0maxPosition 5 0 }

DEF SKULL Transform {translation 0 0 0children [ Inline {url [“skull.wrl”]}]}]}

ROUTE SKULL_DRAG.translation_changed TO SKULL.translation

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

Timers

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

Trigger Logic Timer Engine Target

Viewpoint { position 0 0 15}DEF DETECTOR ProximitySensor {size 25 25 25}DEF TIMER TimeSensor {cycleInterval 2}DEF LIGHT PointLight {

intensity 0location 3 3 3}

Inline {url [“chacmool.wrl”]} #objects to be litROUTE DETECTOR.enterTime TO TIMER.startTimeROUTE TIME.fraction_changed TO LIGHT.intensity

Engines

Convert the output of a time sensor into a change in some other type of value

interpolator & keyframe PositionInterpolator OrientationInterpolator ColorInterpolator ScalarInterpolator CoordinateInterpolator

Trigger Logic Timer Engine Target

DEF Spark_mover PositionInterpolator {key [0,1]keyvalue [0 0 0, 0.8, 5,0]}

ROUTE TIME.fraction_changed TO Spark_mover.set_fractionROUTE Spark_mover.value_changed TO Spark.translation

Example (bike rider - bike.wrl)#VRML V2.0 utf8DEF 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 0children [ Inline { url "rider2.wrl"}]}

DEF T TimeSensor {loop TRUEenabled TRUEcycleInterval 5stopTime -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_fractionROUTE P.value_changed TO BIKE.translationROUTE BIKE.translation TO RIDER.translation

More examples

rider.wrlframe.wrlwheel.wrl

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

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

The script node act as a gateway to the script itself

A node

Scene

translation

color

size

rotation

Script node

url

eventOut

eventin

another node

translation

color

size

rotation

JAVA code

Example (ChangeColor.wrl)#VRML V2.0 utf8Transform { 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}# RoutingROUTE TS.isActive TO ColorScript.clickedROUTE ColorScript.newColor TO SphereColor.set_diffuseColor

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(); } }}

Example II (mover.wrl)#VRML V2.0 utf8DEF 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}# RoutingROUTE TS.isActive TO MoveIt.clicked

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); } }}

JAVA & The script nodegetSize()getValue()get1Value(int index)setValue(value)set1Value(int index, value)addValue(value)insertValue(int index, value)deleteValue(int index)clearValue()

Compiling a JAVA script

Download vrml package (vrml.*)put it in a directory where your classpath

can reach