Motivation
You can group shapes to compose complex shapes
X3D has several grouping nodes, including:
XML Encoding
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| <Group><!-- ... --></Group>
<Switch><!-- ... --></Switch>
<Transform><!-- ... --></Transform>
<Billboard><!-- ... --></Billboard>
<Anchor><!-- ... --></Anchor>
<Inline/>
<!-- and more -->
|
Classic VRML Encoding
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| Group { ... }
Switch { ... }
Transform { ... }
Billboard { ... }
Anchor { ... }
Inline { ... }
and more
|
Syntax: Group
The Group node creates a basic grouping.
- Every child node in the group is displayed.
XML Encoding
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| <Group>
<!-- children ... -->
</Group>
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Classic VRML Encoding
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| Group {
children [ ... ]
}
|
Syntax: Switch
The Switch group node creates a switched group
- Only one child node in the group is displayed
- You select which child
- Children implicitly numbered from 0
- A -1 selects no children
XML Encoding
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| <Switch
whichChoice='0'>
<!-- children ... -->
</Switch>
|
Classic VRML Encoding
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| Switch {
whichChoice 0
children [ ... ]
}
|
The Transform group node creates a group with its own coordinate system.
- Every child node in the group is displayed.
XML Encoding
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| <Transform
translation='0.0 0.0 0.0'
rotation='0.0 1.0 0.0 0.0'
scale='1.0 1.0 1.0'>
<!-- children ... -->
</Transform>
|
Classic VRML Encoding
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| Transform {
translation 0.0 0.0 0.0
rotation 0.0 1.0 0.0 0.0
scale 1.0 1.0 1.0
children [ ... ]
}
|
Syntax: Billboard
The Billboard group node creates a group with a special coordinate system.
- Every child node in the group is displayed.
- The coordinate system is turned to face viewer.
XML Encoding
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| <Billboard
axisOfRotation='0.0 1.0 0.0'>
<!-- children ... -->
</Billboard>
|
Classic VRML Encoding
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| Billboard {
axisOfRotation 0.0 1.0 0.0
children [ ... ]
}
|
Billboard rotation axes
- A rotation axis defines a pole to rotate round
- Similar to a Transform node’s rotation field, but no angle (auto computed)
- A standard rotation axis limits rotation to spin about that axis
- A zero rotation axis enables rotation around any axis
| Rotate about | Axis |
|---|
| X-Axis | 1.0 0.0 0.0 |
| Y-Axis | 0.0 1.0 0.0 |
| Z-Axis | 0.0 0.0 1.0 |
| Any Axis | 0.0 0.0 0.0 |
A sample billboard group
XML Encoding
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| <!-- Y-axis -->
<Billboard
axisOfRotation='0.0 1.0 0.0'>
<Shape><!-- ... --></Shape>
<Shape><!-- ... --></Shape>
<Shape><!-- ... --></Shape>
<!-- ... -->
</Billboard>
|
Classic VRML Encoding
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| Billboard {
# Y-axis
axisOfRotation 0.0 1.0 0.0
children [
Shape { ... }
Shape { ... }
Shape { ... }
...
]
}
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Syntax: Anchor
An Anchor node creates a group that acts as a clickable anchor
- Every child node in the group is displayed
- Clicking any child follows a URL
- A description names the anchor
XML Encoding
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| <Anchor
url='"stairwy.wrl"'
description='Twisty Stairs'>
<!-- children ... -->
</Anchor>
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Classic VRML Encoding
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| Anchor {
url "stairwy.wrl"
description "Twisty Stairs"
children [ ... ]
}
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Syntax: Inline
An Inline node creates a special group from another X3D file’s contents
- Children read from file selected by a URL
- Every child node in group is displayed
XML Encoding
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| <Inline
url='"table.wrl"'/>
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Classic VRML Encoding
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| Inline {
url "table.wrl"
}
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Summary
- The Group node creates a basic group
- The Switch node creates a group with 1 choice used
- The Transform node creates a group with a new coordinate system
- The Billboard node creates a group with a coordinate system that rotates to face the viewer
- The Anchor node creates a clickable group
- Clicking any child in the group loads a URL
- The Inline node creates a special group loaded from another X3D file