1GR2-00 GR2 Advanced Computer Graphics AGR Lecture 11 VRML Animation and Interaction.
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1 GR2-00 GR2 Advanced Computer Graphics AGR Lecture 11 VRML Animation and Interaction
Transcript of 1GR2-00 GR2 Advanced Computer Graphics AGR Lecture 11 VRML Animation and Interaction.
1GR2-00
GR2Advanced Computer
GraphicsAGR
GR2Advanced Computer
GraphicsAGR
Lecture 11VRML Animation and
Interaction
2GR2-00
VRML - The Story So FarVRML - The Story So Far
We have seen how to build hyperlinked, static, non-interactive 3D worlds
#VRML V2.0 utf8
Shape {
geometry Cylinder {
radius 2
height 4
}
appearance Appearance {
material Material {
diffuseColor 1 0 0
specularColor 1 1 1 }
}
}
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Richer WorldsRicher Worlds
VRML97 allows the creation of much more interesting worlds by introducing:– interaction and animation– multimedia– scripting
Worlds become activeactive– can change over time– can change in response to a user’s
actions
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Making Worlds Come AliveMaking 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 eventsevents and sensorssensors
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Sensors and EventsSensors and Events
A sensorsensor 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 eventevent
Events are routedrouted from one node to another to program behaviour in the world
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Routing of EventsRouting 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
NodeA
NodeB
route
eventOuts eventIns
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Example of RoutingExample 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
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Time SensorTime 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
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AnimationAnimation
Animation is achieved by routing time events to an animation animation engine engine
This engine is programmed with keyframe valueskeyframe values– on receiving a time event, it
calculates an ‘in-between’ value– this gets routed to another node,
typically a transform node
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Interpolator NodesInterpolator Nodes
These form the animation engines Example is Orientation InterpolatorOrientation 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
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AnimationAnimation
Animation then achieved by routing time events from a time sensor to the animation engine...animation engine...
... which then drives say a transform node:
TIMESENSOR
time elapsed
ROTATIONINTERPOL-ATOR
rotation
TRANSFORM
animation enginesensor
event event
modify geometry
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Rotating SignRotating 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
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User Activated SensorsUser Activated Sensors
Another set of sensor nodes generate events in response to user actions
A TouchSensorTouchSensor 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
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Touch Sensor ExampleTouch 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
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Proximity SensorProximity 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
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Proximity Sensor ExampleProximity 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
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Other SensorsOther Sensors
Drag sensors– PlaneSensor– CylinderSensor– SphereSensor
these constrain the allowable motion
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Collision DetectionCollision 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
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SoundSound
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
*
location full intensity
sound fades
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Collision + Sound ExampleCollision + 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
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MoviesMovies
Textures can be movies rather than static images
Use the MovieTexture node...
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User Control of VRML Worlds
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– JavaJava 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
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ScriptingScripting
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 animationTIME
SENSOR
SCRIPTNODE
VIEWPOINT
time elapsed position
java code
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Example of ScriptingExample 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 beassigned to eachvertex and smoothlyinterpolated
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Example of Scripting - Dynamic Change of
Surface
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_fractioneventOut MFFloat new_heighturl:javascript<JavaScript code goes here, to createnew set of heights at grid points, based on time>}
ROUTE TIMER.fraction_changed TO ENGINE.time_fractionROUTE ENGINE.new_colour TO GRID.set_height
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Linking Software to VRML Worlds
Linking Software to VRML Worlds
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
script node
VRML node
Java applet
VRML node
VRML world VRML world
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External Authoring Interface
External Authoring Interface
Allows communication between a Java applet and a VRML world..
Here is a virtual shopping mall..
Clicking on a TouchSensorover an object sends eventto Java applet which keepsrecord of purchases
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BrowsingBrowsing
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)
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AuthoringAuthoring
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
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FuturesFutures
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
