Building an X3D World

X3D file structure

X3D files contain:

• The file header
• Comments - notes to yourself
• Nodes - nuggets of scene information
• Fields - node attributes you can change
• Values - attribute values
• Routes - connections between fields
• more …

A sample X3D file

XML Encoding

<?xml version="1.0" encoding="UTF-8"?>
<X3D profile='Full' version='4.0' xmlns:xsd='http://www.w3.org/2001/XMLSchema-instance' xsd:noNamespaceSchemaLocation='http://www.web3d.org/specifications/x3d-4.0.xsd'>
  <Scene>
  <!-- A Cylinder -->
  <Shape>
    <Appearance>
      <Material/>
    <Appearance>
    <Cylinder
        height='2.0'
        radius='1.5'/>
    </Shape>
  </Scene>
</X3D>

Classic VRML Encoding

#X3D V4.0 utf8
# A Cylinder
Shape {
  appearance Appearance {
    material Material { }
  }
  geometry Cylinder {
    height 2.0
    radius 1.5
  }
}

Example

• Download ZIP Archive
• View Source in Playground

Understanding the header

#X3D V4.0 utf8

• #X3D: File contains X3D text
• V4.0 : Text conforms to version 4.0 syntax
• utf8 : Text uses UTF8 character set

Understanding UTF8

• utf8 is an international character set standard
• utf8 stands for:
  • UCS (Universal Character Set) Transformation Format, 8-bit
  • Can encodes up to 2,164,864 characters for many languages
  • ASCII is a subset

Using comments

# A Cylinder

• Comments start with a number-sign (#) and extend to the end of the line

Using nodes

XML Encoding

<Cylinder/>

Classic VRML Encoding

Cylinder {
}

• Nodes describe shapes, lights, sounds, etc.
• Every node has:
  • A node type (Shape, Cylinder, etc.)
  • A pair of curly-braces
  • Zero or more fields inside the curly-braces

Using node type names

Node type names are case sensitive:

• Each word starts with an upper-case character
• The rest of the word is lower-case

Some examples:

Appearance, Cylinder, Material, Shape

Using fields and values

XML Encoding

<Cylinder
    height='2.0'
    radius='1.5'/>

Classic VRML Encoding

Cylinder {
  height 2.0
  radius 1.5
}

• Fields describe node attributes

Every field has:

• A field name (height, radius, etc.)
• A data type (float, integer, etc.)
• A default value
• Different node types have different fields
• Fields are optional
  • A default value is used if a field is not given
• Fields can be listed in any order
  • The order doesn’t affect the node

Placing nodes

Every node has a »containerField« attribute with a default value, which is different for each node type. You can change the value if needed.

<Collision>
  <Shape containerField='proxy'>
    <Box/>
  </Shape>
  <Transform>
    <!-- ... -->
  </Transform>
</Collision>

Summary

• The file header gives the version and encoding
• Nodes describe scene content
• Fields and values specify node attributes
• containerField attribute can be changed.
• Everything is case sensitive