Event Routing

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
• _changedoutgoing event
• translation_changed
• ROUTE Xform1.translation_changed TO
  Xform2.set_translation
• ROUTE Xform1.translation TO Xform2.translation

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ROUTE

• Routing should be done in same type (field)
• a set_ or _changed event is the same type as the
  exposed field its 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
Logic
Timer
Engine
Target

• 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

7
The Animation Event Path
Trigger
Logic
Timer
Engine
Target

• Target The browser sends the Engines output
  to a relevant node in the scene hierarchy, whoses
  field values changes accordingly

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 Soun
d 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_ch
anged 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
  --gt 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
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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_c
hanged TO Spark_mover.set_fraction ROUTE
Spark_mover.value_changed TO Spark.translation
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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
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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
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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()
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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
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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.getV
alue()) position (SFVec3f)(node.getExp
osedField("translation"))
position.setValue((position.getX() 5), 0, 0)

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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).

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• 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 400 pm
  of 10/8/2001.