VRML -> X3D
Introducing
X3D
X3D XML Syntax Overview (2)
The Actual Transcoding
Now, a quick study of the existing VRML97 definitions and syntax, before developing the XML encoding.
Basic VRML97 Syntax
Shape
VRML97 Spec IDL:
Shape {
exposedField SFNode appearance NULL
exposedField SFNode geometry NULL
}
X3D Spec IDL:
Shape : ShapeNodeType {
field [in, out] SFNode appearance NULL;
field [in, out] SFNode geometry NULL;
}
Changed Notation:
X3D VRML97
field [in, out] = exposedField
field [] = field (initialize only)
event [in] = eventIn
event [out] = eventOut
Definition:
NodeName : AbstractionNode {
field|event [in,out|in|out] VarType NodeOrFieldName
NodeOrFieldDefault|NULL
[min,max|list];
...
}
field|event = field or event
[in,out] or [in] or [out] access,
VarType = Node/Field Type from official list,
Node or field name from official list,
Node/field initial or default value or NULL, and,
[min,max|list] used for Fields to show
acceptable value =
min.max = numeric range. Examples:
[0,1] = range 0 to 1
(-inf,inf) = any signed number
[-1,inf) = any number egt -1
(0,1] = allow value of one but not zero
list = choice of values. Example:
[TRUE|FALSE] = either TRUE or FALSE is accepted.
For Example:
Appearance : X3DNode {
field [in,out] SFNode material NULL;
field [in,out] SFNode texture NULL;
field [in,out] SFNode textureTransform NULL;
}
(Nodes don't use the [min,max|list] definition.)
Material : MaterialNode {
field [in, out] SFFloat ambientIntensity 0.2 [0,1];
field [in, out] SFColor diffuseColor 0.8 0.8 0.8 [0,1];
field [in, out] SFColor emissiveColor 0 0 0 [0,1];
field [in, out] SFFloat shininess 0.2 [0,1];
field [in, out] SFColor specularColor 0 0 0 [0,1];
field [in, out] SFFloat transparency 0 [0,1];
}
[0,1] applies to each numeric component of the value.
Shape, Appearance.
The Shape node has two fields, appearance and geometry,
which are used to create rendered objects in the world.
The appearance field contains an Appearance node that
specifies the visual attributes (e.g., material and texture)
to be applied to the geometry. The geometry field contains a
geometry node.
The specified geometry node is rendered with the specified
appearance nodes appled.
Basic VRML97 Syntax
appearance texture nodes
Texturing :
ImageTexture
MovieTexture
PixelTexture
ImageTexture : TextureNodeType {
field [in, out] MFUrl url [NULL] ["urn"]
field [] SFBool repeatS; TRUE [TRUE|FALSE]
field [] SFBool repeatT; TRUE [TRUE|FALSE]
}
MovieTexture : TextureNodeType {
field [in, out] SFBool loop FALSE
field [in, out] SFFloat speed 1.0 [-∞,∞];
field [in, out] SFTime startTime 0 [-∞,∞];
field [in, out] SFTime stopTime 0 [-∞,∞];
field [in, out] MFUrl url [NULL] ["urn"];
field [] SFBool repeatS TRUE [TRUE|FALSE]
field [] SFBool repeatT TRUE [TRUE|FALSE]
event [out] SFTime duration_changed;
event [out] SFBool isActive;
}
TextureTransform : TextureTransformNodeType {
field [in, out] SFVec2f center 0 0 [-∞,∞];
field [in, out] SFFloat rotation 0 [-∞,∞];
field [in, out] SFVec2f scale 1 1 [-∞,∞];
field [in, out] SFVec2f translation 0 0 [-∞,∞];
}
Texture can contain ImageTexture, MovieTexture, or PixelTexture nodes.
Default texture mapping.
Basic VRML97 Syntax
geometry
field [in, out] SFNode geometry NULL Box Cone Cylinder ElevationGrid Extrusion IndexedFaceSet IndexedLineSet PointSet Sphere Text Geometry nodes created from PROTOs or EXTERNPROTOs Humanoid Parameteric Volumetric Hypermetric Hypermultimetric Plus new stuff ...
There is not now or was ever a node named geometry. It is a container field for one of the geometry nodes: Box, Cone, Cylinder, ElevationGrid, Extrusion, IndexedFaceSet, IndexedLineSet and all.
Basic VRML97 Syntax
IndexedFaceSet
IndexedFaceSet : GeometryNodeType {
event [in] MFInt32 set_colorIndex;
event [in] MFInt32 set_coordIndex;
event [in] MFInt32 set_normalIndex;
event [in] MFInt32 set_texCoordIndex;
field [in, out] SFNode color; NULL
field [in, out] SFNode coord; NULL
field [in, out] SFNode normal; NULL
field [in, out] SFNode texCoord; NULL
field [] SFBool ccw; TRUE [-1|int];
field [] MFInt32 colorIndex; [coordIndex] [-1|int];
field [] SFBool colorPerVertex; TRUE [TRUE|FALSE]
field [] SFBool convex; TRUE [TRUE|FALSE]
field [] MFInt32 coordIndex; [NULL] [-1|int]
field [] SFFloat creaseAngle; 0 [0,∞)
field [] MFInt32 normalIndex; [coordIndex] [-1|int]
field [] SFBool normalPerVertex; TRUE [TRUE|FALSE]
field [] SFBool solid; TRUE [TRUE|FALSE]
field [] MFInt32 texCoordIndex; [coordIndex] [-1|int]
}
Each face of the IndexedFaceSet shall have:
- at least three non-coincident vertices,
- vertices that define a planar polygon,
- vertices that define a non-self-intersecting polygon.
Otherwise, results are undefined.
Color : ColorNodeType {
field [in, out] MFColor color [NULL] [0,1]
}
Coordinate : CoordinateNodeType {
field [in, out] MFVec3f point [NULL] [-∞,∞]
}
Normal : NormalNodeType {
field [in, out] MFVec3f vector [computed] [-∞,∞]
}
TextureCoordinate : TextureCoordinateNodeType {
field [in, out] MFVec2f point [computed] [-∞,∞]
}
Here is the IndexedfaceSet IDL.
It shows that the Color, Coordinate, Normal, TextureCoordinate
are nodes.
If color, normal, texCoord points, or colorIndex, texCoordIndex, or normalIndex
are NULL, then coord point or coordIndex is used.
Basic VRML97 Syntax
A Result
Shape {
appearance Appearance {
material Material {
ambientIntensity 0.2
diffuseColor 0.8 0.8 0.8
emissiveColor 0 0 0
shininess 0.2
specularColor 0 0 0
transparency 0
}
texture ImageTexture {
url ["somePic.jpeg"]
repeatS TRUE
repeatT TRUE
}
textureTransform TextureTransform {
center 0 0
rotation 0
scale 1 1
translation 0 0
}
}
geometry IndexedFaceSet {
ccw TRUE
convex TRUE
creaseAngle 0
solid TRUE
coord Coordinate {point[ x y z, ... ] }
coordIndex [ v1 v2 v3 ... -1, ... ]
colorPerVertex TRUE
color Color {color [r g b, ... ] }
colorIndex [ v1 v2 v3 ... -1, ...]
texCoord TextureCoordinate {point [ x y z, ... ]}
texCoordIndex [ v1 v2 v3 ... -1, ...]
normalPerVertex TRUE
normal Normal {vector[x y z, ... ] }
normalIndex [ v1 v2 v3 ... -1, ... ]
}
}
The coord Coordinate point gives the x,y,z for each vertex.
The coordIndex identifies the vertices in the polygon by
order in coord Coordinate point,
then closing the polygon with -1.
Basic XML Syntax
Elements contain Content and Attributes
The Basic Content Tagset:
<tagname attr1='string' >
... content ...
</tagname >
attribute is name and value pair: name='value'
The Empty Element:
<tagname attr2="string' />
Elements can be Content:
<tag1>
<tag2 />
<tag3>
<tag4 />
</tag3>
</tag1>
XML Namespaces:
tagname = namespace:tagname
attrname = namespace:attrname
value space - lexical space - facets
The tagset for a basic element consists of a start tag and an end tag.
Everything between the start and end tags is called content.
Content can be another set of tags.
If the element does not contain content, only attributes,
the
begin and end tags can be combined as shown in this example of an empty
element.
Elements can be content: Here the element called tag1 contains
the empty element called tag2, along with the element called tag3,
which in turn contains the element called tag4.
The tagname and attrname (atribute name) actually consist of two
parts, an XML namespace, and the tagname. The XML namespace is defined by the
XML schema and is a slightly different concept than the typical use
of the term in programmng because it allows definiton of the structure of the
subject element. And an amazing thing about it is that some item way down
in the middle of a structure can obtain its identity from a completely
different environment than any other items in the structure.
X3D XML Shape
X3D Spec IDL:
Shape : ShapeNodeType {
field [in, out] SFNode appearance NULL
field [in, out] SFNode geometry NULL
}
X3D XML Encoding:
<Shape >
...
</Shape >
<Shape >
appearance
geometry
</Shape >
So that is what it begins to look like. We have a Shape element and place to add appearance and geometry. Now let's look at the X3D XML Schema for more detail.
X3D XML Shape Schema
<xsd:element name="Shape"> <xsd:element ref="Appearance"/> <xsd:element ref="IndexedFaceSet" /> </xsd:element>
Yes, that is a bit too simple, we really need:
<xsd:element name="Shape">
<xsd:attribute name="DEF" type="IDREF"/>
<xsd:element ref="Appearance"/>
<xsd:group ref="GeometryContentModel"/>
</xsd:element>
<xsd:group name="GeometryContentModel">
<xsd:choice>
<xsd:element ref="IndexedFaceSet"/>
<xsd:element ref="IndexedLineSet"/>
<xsd:element ref="PointSet"/>
...
<xsd:element ref="Nurbs"/>
</xsd:choice>
</xsd:group>
XML Schema Definition of Group:
<group name = NCName>
Content: ((all | choice | sequence))
</group>
Shape, GeometryContentModel, Appearance
X3D XML IndexedFaceSet Schema
And the Schema looks like:
<xsd:element name="IndexedFaceSet">
<xsd:attribute name="DEF" type="IDREF"/>
<xsd:attribute name="ccw" type="Boolean" default="TRUE" />
<xsd:attribute name="convex" type="Boolean"default="TRUE" />
<xsd:attribute name="creaseAngle" type="Float" default="0" />
<xsd:attribute name="colorPerVertex" type="Boolean" default="TRUE" />
<xsd:attribute name="normalPerVertex" type="Boolean" default="TRUE" />
<xsd:attribute name="solid" type="Boolean" default="TRUE" />
<xsd:attribute name="coordIndex" type="Integers"/>
<xsd:attribute name="colorIndex" type="Integers"/>
<xsd:attribute name="normalIndex" type="Integers"/>
<xsd:attribute name="texCoordIndex" type="Integers"/>
<xsd:element name="Coordinate">
<xsd:attribute name="point" type="Vector3FloatArray"/>
</xsd:element>
<xsd:element name="ColorNode">
<xsd:attribute name="color" type="Colors"/>
</xsd:element>
<xsd:element name="Normal">
<xsd:attribute name="vector" type="Vector3FloatArray"/>
</xsd:element>
<xsd:element name="TextureCoordinate">
<xsd:attribute name="point" type="Vector2FloatArray"/>
</xsd:element>
</xsd:element>
From the diagram:
GeometryNodeType
IndexedFaceSet
ccw='Boolean'
colorIndex='Integers'
colorPerVertex='Boolean'
convex='Boolean'
coordIndex='Integers'
creaseAngle='Float'
normalIndex='Integers'
normalPerVertex='Boolean'
solid='Boolean'
texCoordIndex='Integers'
GeometricPropertyNode
ColorNodeType
CoordinateNodeType
NormalNodeType
TextureCoordinateNodeType
GeometricPropertyNodeType
ColorNodeType
ColorNode color='Colors'
CoordinateNodeType
Coordinate point='Vector3FloatArray
NormalNodeType
Normal vector='Vector3FloatArray'
TextureCoordinateNodeType
TextureCoordinate point='Vector2FloatArray'
Gives us:
<IndexedFaceSet
ccw='Boolean'
normalPerVertex='Boolean'
colorPerVertex='Boolean'
convex='Boolean'
solid='Boolean'
creaseAngle='Float'
coordIndex='Integers'
colorIndex='Integers'
normalIndex='Integers'
texCoordIndex='Integers' >
<Coordinate point='Vector3FloatArray />
<ColorNode color='Colors' />
<Normal vector='Vector3FloatArray' />
<TextureCoordinate point='Vector2FloatArray' />
</IndexedFaceSet>
element name="IndexedFaceSet"
* coordIndex used if colorIndex or normalIndex is NULL.
* default texCoordIndex provided if NULL.
web3d x3d syntax
Welcome to a discussion of the XMLization and DOMification of VRML.