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Chapter 3:
Node Reference
Intro
Anchor
Appearance
AudioClip
Background
Billboard
Box
Collision
Color
ColorInterpolator
Cone
Coordinate
CoordinateInterpolator
Cylinder
CylinderSensor
DirectionalLight
ElevationGrid
Extrusion
Fog
FontStyle
Group
ImageTexture
IndexedFaceSet
IndexedLineSet
Inline
LOD
Material
MovieTexture
NavigationInfo
Normal
NormalInterpolator
OrientationInterpolator
PixelTexture
PlaneSensor
PointLight
PointSet
PositionInterpolator
ProximitySensor
ScalarInterpolator
Script
Shape
Sound
Sphere
SphereSensor
SpotLight
Switch
Text
TextureCoordinate
TextureTransform
TimeSensor
TouchSensor
Transform
Viewpoint
VisibilitySensor
WorldInfo
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ColorInterpolator {
eventIn SFFloat set_fraction # (- ,)
exposedField MFFloat key [] # (-,)
exposedField MFColor keyValue [] # [0,1]
eventOut SFColor value_changed
}
This node interpolates among a set of MFColor key values to produce
an SFColor (RGB) value_changed event. The number of colours in
the keyValue field shall be equal to the number of keyframes
in the key field. The keyValue field and value_changed
events are defined in RGB colour space. A linear interpolation using
the value of set_fraction as input is performed in HSV space
(see [FOLE] for description of RGB and
HSV colour spaces). Results are undefined when interpolating between
two consecutive keys with complementary hues.
Section "2.6.8 Interpolators" contains
a detailed discussion of interpolators.
| TIP:
The ColorInterpolator outputs an SFColor, suitable for use in any
of the color fields of a Material node (diffuseColor, specularColor,
emissiveColor). Unfortunately, a ColorInterpolator cannot
be used to interpolate multiple colors (it does not generate an
MFColor output) and so cannot be used with a Color node. If you
do need to change the colors in a Color node, you will have to write
a Script that does the appropriate calculations. |
| TECHNICAL
NOTE:
Defining the keys in RGB space but doing the interpolation in
HSV space may seem somewhat strange. If the key values are very
close together, then the differences between the two spaces are
minimal. However, if there are large differences between the keys,
then doing the interpolation in HSV space gives better perceptual
results, since interpolating between two keys with the same intensity
will not result in any intensity changes. That isn't true of RGB
space: Interpolate from full-intensity red (1,0,0) to full-intensity
green (0,1,0) and halfway you'll get half-intensity yellow (0.5,0.5,0).
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EXAMPLE
(click to run):
The following example illustrates the use of the ColorInterpolator
node. An infinitely looping TimeSensor is routed to a ColorInterpolator
that is routed to the diffuseColor of a Material that
is coloring the Box, Sphere, and Cone:
#VRML V2.0 utf8
Transform { children [
Transform {
translation -4 0 0
children Shape {
geometry Box {}
appearance DEF A Appearance {
material DEF M Material { diffuseColor .8 .2 .2 }
}
}
}
Transform {
translation 0 0 0
children Shape { geometry Sphere {} appearance USE A }
}
Transform {
translation 4 0 0
children Shape { geometry Cone {} appearance USE A }
}
NavigationInfo { type "EXAMINE" }
]}
DEF CI ColorInterpolator {
key [ 0 .2 .4 .6 .8 1 ]
keyValue [ .8 .2 .2, .2 .8 .2, .2 .2 .8, .8 .8 .8,
1 0 1, .8 .2 .2 ]
}
DEF TS TimeSensor { loop TRUE cycleInterval 5 }
ROUTE TS.fraction_changed TO CI.set_fraction
ROUTE CI.value_changed TO M.set_diffuseColor
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