X3D grouping and transforms
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Introduction
Grouping nodes organize objects in an X3D world in various ways. There existe several grouping nodes that have different functions.
- Group and StaticGroup collect related nodes together. This way one can reuse it as a whole
- Transform is probably the most important node. It controls position, orientation and scale of its children
- Inline loads other X3D scenes
- LOD (level of detail) provides different levels of geometry quality according to the user's viewpoint
- Switch can be animated to select different children, one (or none) at a time
- Anchor allows to define URL links to another X3D scene or other page in a web browser
- Billboard allows to create a group whose geometry always faces the user
- Collision provides collision detection properties between child geometry and the camera.
Inlining other scenes
The Inline node allows to loads another X3D world within the current scene.
The supported formats depend on the user's X3D browser: XML encoded .x3d, ClassicVRML encoding .x3dv, compressed binary .x3db, sometimes VRML97 .wrl
- Inlined scene must be positioned, rotated and scaled to match the local frame of coordinates
- The local reference frame is determined by the parent's Transformation node hierarchy, i.e. where it is loaded.
- Also, the user's viewpoint does not change automatically to the loaded Inline scene's default Viewpoint
The Inline node takes the following Fields (and some more). The url attribute is mandatory of course, all the others are optional.
- url 'list of URLs'
- is one or more quoted strings that all point to the same object in one or more locations. Each address is retrieved and evaluated, in order, until the desired Inline file is successfully retrieved. Relative addresses work both on localhost or server. Absolute addresses provide a reliable backup
- bboxCenter "0 0 0"
- Bounding box center: position offset from origin of local coordinate system.
- bboxSize "-1 -1 -1"
- the bounding box size is automatically calculated, but it can be specified as an optimization or constraint.
Look at the Group example world below.
Grouping
The Group node collects nodes together with related purpose. Often such nodes are close to each other spatially.
If a DEF is provided, the group can be re-USEd.
Below is an example of scene made with only 3 Shapes. We define a house with a cube and cylinder and then reuse it twice.
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE X3D PUBLIC "ISO//Web3D//DTD X3D 3.2//EN" "../../schemas/x3d-3.2.dtd">
<X3D profile='Interchange' version='3.1' xmlns:xsd='http://www.w3.org/2001/XMLSchema-instance' xsd:noNamespaceSchemaLocation='http://www.web3d.org/specifications/x3d-3.1.xsd'>
<head>
<meta content='house.x3d' name='title'/>
<meta content='Example for Group node' name='description'/>
</head>
<Scene>
<!-- create an almost white background for printing -->
<Background skyColor='0.9 0.9 0.9'/>
<!-- define a house as a cube with a cone on top -->
<Group DEF='House'>
<Transform translation="0 1 0">
<Shape>
<Appearance>
<Material diffuseColor='1 1 0'/>
</Appearance>
<Box/>
</Shape>
</Transform>
<Transform translation="0 2.5 0">
<Shape DEF='Roof'>
<Appearance>
<Material diffuseColor='1 0 0'/>
</Appearance>
<Cone bottomRadius="2" height="1">
</Cone>
</Shape>
</Transform>
</Group>
<!-- reuse, make smaller and put on top of the house -->
<Transform translation="0 2.5 0" scale="0.5 0.5 0.5">
<Shape USE="House"/>
</Transform>
<!-- reuse, squeeze and put aside -->
<Transform translation="3.5 0 0" scale="1.0 0.5 0.5">
<Shape USE="House"/>
</Transform>
<Inline Center="0.0 0.0 0.0" bboxSize="10.5 10.5 10.5" url="../common/coordinates.x3d"/>
<Transform translation="0 -0.05 0">
<Shape DEF="floor">
<Appearance>
<Material diffuseColor='0 1 0'/>
</Appearance>
<Cylinder height="0.1" radius="5"/>
</Shape>
</Transform>
<Inline url='"../common/coordinates.x3d" "http://tecfa.unige.ch/guides/x3d/ex/common/coordinates.x3d"'/>
</Scene>
</X3D>