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VRML Script Tutorial
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VRML Interactive Tutorial

Introduction
VRML File Structure
Drawing: Shape node
Geometry Nodes:
Box
Sphere
Cone
Cylinder
PointSet
IndexedLineSet
IndexedFaceSet
Extrusion
ElevationGrid
Example: Chessboard
Text
FontStyle
Appearance
Material
Textures
Image Texture
Movie Texture
Pixel Texture
Texture Coordinate
Texture Transform
Let there be Light
Directional Light
Point Light
Spot Light
Materials with Colored Lights
Hierarchical Node Structures
Group
Transform
Collision
Anchor
Billboard
Switch
Inlining Files
Defining and Instancing Nodes
Defining Levels of Detail
Events in VRML
Creating Paths between events: ROUTE
Generating Events based on Timers or User Actions
Timers
Touch Sensor
Visibility Sensor
Dragging Sensors
Plane Sensor
Sphere Sensor
Cylinder Sensor
Proximity Sensors
Example: Proximity sensor
Interpolators
Color
Coordinate
Normal
Orientation
Position
Scalar
Example
Let the Music Play
Sound
AudioClip
Bindable Nodes
Who Am I: NavigationInfo
Where Am I: ViewPoint
Adding Realism to the world
Background
Fog
Information about your world
WorldInfo
Definition for Auxiliary Nodes
Coordinate
Color
Normal

PositionInterpolator


The PositionInterpolator node is an interpolator which takes a list of 3D coordinate values in the field keyValue.

For a list of the events of this node see interpolator.

Syntax:
PositionInterpolator {
key [ ]
keyValue[ ]
}


This interpolator is used to animate objects, moving them along the path specified in keyValue

A complete example is now presented. A Shape is drawn at the origin. The PositionInterpolator will move the shape up and down along the y axis. The cycle is repeated forever.

First one needs the to define a Transform with a Shape, a TimeSensor, and a PositionInterpolator.

Example:
#VRML V2.0 utf8

DEF tr Transform {
children [
Shape {
appearance Appearance {
material DEF mat Material { diffuseColor 1 0 0 }
}
geometry Sphere {}
}
DEF pi PositionInterpolator {
key [ 0 1 ]
keyValue [ 0 0 0, 0 1 0, 0 0 0]
}
DEF ts TimeSensor {
cycleInterval 2
loop TRUE
}
]
}


Now the only thing which is missing is routing the events.

We need to get the eventOut fraction_changed generated by the TimeSensor. This event outputs a value between 0 and 1. We can use this value to set a key for the PositionInterpolator by routing the fraction_changed eventOut from the TimeSensor to the set_fraction eventIn from the PositionInterpolator.

A new fraction being set in an interpolator causes the keyValue to be changed. As a consequence the interpolator will generate the fraction_changed eventOut. Because the interpolator used is a PositionInterpolator, this event outputs a 3D coordinate value.

Finally we use this eventOut to set a translation in the Transform node. Because the translation is an exposed field of the Transform node we can use the eventIn set_translation to change it. To do this we route the fraction_changed eventOut of the PositionInterpolator to the set_translation eventIn of the Transform node.

The ROUTE statements to do this are:
ROUTE ts.fraction_changed TO pi.set_fraction
ROUTE pi.value_changed TO tr.set_translation
Note that the nodes being routed are given a name using the DEF statement. This is because a name is required in a ROUTE statement.



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