6.34
IndexedFaceSet
The IndexedFaceSet node represents a 3D shape formed by constructing
faces (polygons) from vertices listed in the coord field. The coord
field contains a Coordinate or GeoCoordinate node that defines the 3D vertices referenced
by the coordIndex field. IndexedFaceSet uses the indices in its coordIndex
field to specify the polygonal faces by indexing into the coordinates in
the Coordinate or GeoCoordinate node. An index of "-1" indicates that the current
face has ended and the next one begins. The last face may be (but does not
have to be) followed by a "-1" index. If the greatest index in
the coordIndex field is N, the Coordinate or GeoCoordinate node shall contain N+1
coordinates (indexed as 0 to N). 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, The results are undefined.
The IndexedFaceSet node is specified in the local coordinate system and
is affected by the transformations of its ancestors.
Descriptions of the coord, normal, and texCoord
fields are provided in the Coordinate, Normal, and TextureCoordinate
nodes, respectively.
Details on lighting equations and the interaction between color
field, normal field, textures, materials, and geometries are provided
in 4.14, Lighting model.
If the color field is not NULL, it shall contain a Color node
whose colours are applied to the vertices or faces of the IndexedFaceSet
as follows:
- If colorPerVertex is FALSE, colours are applied to each face,
as follows:
- If the colorIndex field is not empty, then one colour is used
for each face of the IndexedFaceSet. There shall be at least as many indices
in the colorIndex field as there are faces in the IndexedFaceSet.
If the greatest index in the colorIndex field is N, then there shall
be N+1 colours in the Color node. The colorIndex field shall not
contain any negative entries.
- If the colorIndex field is empty, then the colours in the Color
node are applied to each face of the IndexedFaceSet in order. There shall
be at least as many colours in the Color node as there are faces.
- If colorPerVertex is TRUE, colours are applied to each vertex,
as follows:
- If the colorIndex field is not empty, then colours are applied
to each vertex of the IndexedFaceSet in exactly the same manner that the
coordIndex field is used to choose coordinates for each vertex from
the Coordinate or GeoCoordinate node. The colorIndex field shall contain at least
as many indices as the coordIndex field, and shall contain end-of-face
markers (-1) in exactly the same places as the coordIndex field.
If the greatest index in the colorIndex field is N, then there shall
be N+1 colours in the Color node.
- If the colorIndex field is empty, then the coordIndex
field is used to choose colours from the Color node. If the greatest index
in the coordIndex field is N, then there shall be N+1 colours in
the Color node.
If the color field is NULL, the geometry shall be rendered normally
using the Material and texture defined in the Appearance node (see 4.14, Lighting model, for details).
If the normal field is not NULL, it shall contain a Normal node
whose normals are applied to the vertices or faces of the IndexedFaceSet
in a manner exactly equivalent to that described above for applying colours
to vertices/faces (where normalPerVertex corresponds to colorPerVertex
and normalIndex corresponds to colorIndex). If the normal
field is NULL, the browser shall automatically generate normals, using creaseAngle
to determine if and how normals are smoothed across shared vertices (see
4.6.3.5, Crease angle field).
If the texCoord field is not NULL, it shall contain a TextureCoordinate node. The texture coordinates
in that node are applied to the vertices of the IndexedFaceSet as follows:
- If the texCoordIndex field is not empty, then it is used to
choose texture coordinates for each vertex of the IndexedFaceSet in exactly
the same manner that the coordIndex field is used to choose coordinates
for each vertex from the Coordinate or GeoCoordinate node. The texCoordIndex field
shall contain at least as many indices as the coordIndex field,
and shall contain end-of-face markers (-1) in exactly the same places as
the coordIndex field. If the greatest index in the texCoordIndex
field is N, then there shall be N+1 texture coordinates in the TextureCoordinate
node.
- If the texCoordIndex field is empty, then the coordIndex
array is used to choose texture coordinates from the TextureCoordinate
node. If the greatest index in the coordIndex field is N, then there
shall be N+1 texture coordinates in the TextureCoordinate node.
If the texCoord field is NULL, a default texture coordinate mapping
is calculated using the local coordinate system bounding box of the shape.
The longest dimension of the bounding box defines the S coordinates, and
the next longest defines the T coordinates. If two or all three dimensions
of the bounding box are equal, ties shall be broken by choosing the X, Y,
or Z dimension in that order of preference. The value of the S coordinate
ranges from 0 to 1, from one end of the bounding box to the other. The T
coordinate ranges between 0 and the ratio of the second greatest dimension
of the bounding box to the greatest dimension. Figure
6.10 illustrates the default texture coordinates for a simple box shaped
IndexedFaceSet with an X dimension twice as large as the Z dimension and
four times as large as the Y dimension. Figure 6.11
illustrates the original texture image used on the IndexedFaceSet used in
Figure 6.10.
Figure 6.10 -- IndexedFaceSet texture default mapping
Figure 6.11 -- ImageTexture for IndexedFaceSet in Figure 6.10
Subclause 4.6.3, Shapes and geometry,
provides a description of the ccw, solid, convex, and
creaseAngle fields.
version 1.3.9.1.
