ISO/IEC 14496-16:2011/Amd 1:2011
(Amendment)Information technology — Coding of audio-visual objects — Part 16: Animation Framework eXtension (AFX) — Amendment 1: Efficient representation of 3D meshes with multiple attributes
Information technology — Coding of audio-visual objects — Part 16: Animation Framework eXtension (AFX) — Amendment 1: Efficient representation of 3D meshes with multiple attributes
Technologies de l'information — Codage des objets audiovisuels — Partie 16: Extension du cadre d'animation (AFX) — Amendement 1: Représentation efficace de mailles 3D avec attributs multiples
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Standards Content (Sample)
INTERNATIONAL ISO/IEC
STANDARD 14496-16
Fourth edition
2011-11-01
AMENDMENT 1
2011-12-01
Information technology — Coding of
audio-visual objects —
Part 16:
Animation Framework eXtension (AFX)
AMENDMENT 1: Efficient representation of
3D meshes with multiple attributes
Technologies de l'information — Codage des objets audiovisuels —
Partie 16: Extension du cadre d'animation (AFX)
AMENDEMENT 1: Représentation efficace de mailles 3D avec attributs
multiples
Reference number
ISO/IEC 14496-16:2011/Amd.1:2011(E)
©
ISO/IEC 2011
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ISO/IEC 14496-16:2011/Amd.1:2011(E)
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ISO/IEC 14496-16:2011/Amd.1:2011(E)
Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are members of
ISO or IEC participate in the development of International Standards through technical committees
established by the respective organization to deal with particular fields of technical activity. ISO and IEC
technical committees collaborate in fields of mutual interest. Other international organizations, governmental
and non-governmental, in liaison with ISO and IEC, also take part in the work. In the field of information
technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of the joint technical committee is to prepare International Standards. Draft International
Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as
an International Standard requires approval by at least 75 % of the national bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights.
Amendment 1 to ISO/IEC 14496-16:2011 was prepared by Joint Technical Committee ISO/IEC JTC 1,
Information technology, Subcommittee SC 29, Coding of audio, picture, multimedia and hypermedia
information.
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ISO/IEC 14496-16:2011/Amd.1:2011(E)
Information technology — Coding of audio-visual objects —
Part 16:
Animation Framework eXtension (AFX)
AMENDMENT 1: Efficient representation of 3D meshes with multiple
attributes
Add the following new 4.3.6 and renumber the curent 4.3.6 as 4.3.7:
4.3.6 Region-based representation of 3D meshes with multiple attributes
4.3.6.1 Introduction
The IndexedRegionSet (IRS) node specified in the next Subclause is based on the IndexedFaceSet (IFS)
one but, thanks to its associated Region node, described as well below, it allows to group the faces of an IFS
into subsets, or regions, to represent more naturally and code more efficiently 3D meshes of which some
vertices have multiple attributes (colors, normal vectors or texture coordinates). The IRS concept is very
adequate, for instance, to represent a mesh onto which several textures (one per mesh region) must be
mapped. In this respect, IRS is somewhat related to the MultiTexture[Coordinate] nodes specified in 4.4.3,
but IRS is more general, since it is not specifically designed for blending different textures in view-dependent
rendering applications, nor exclusively targeted at specifying several texture coordinates per vertex. Indeed, it
is for example also possible to model and code with very few bits, thanks to IRS, 3D objects such as a dice
(i.e., a cube) with one solid color per square face as a triangle mesh with six regions of two triangles each. A
similar result could be achieved with IFS, thanks to its per corner mapping of attributes, but this would be less
efficient from a bitstream size viewpoint.
region 1
crease
region 2
corner
vertex
face
region 3
Figure Amd1.1 — A vertex shared by three regions
Figure Amd1.1 shows a triangle mesh vertex shared by eight triangles but only three regions, since just three
of the edges incident to the vertex are part of region creases/frontiers. Region 1 contains three of the triangles
shared by the vertex (and possibly others, not shown) whereas region 2 contains four and region 3 only one.
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ISO/IEC 14496-16:2011/Amd.1:2011(E)
Defining mesh regions allows to specify attributes (not only texture coordinates) on a per wedge [39] basis, as
well as to manage different texture images inside a single IRS node — note that this is impossible with the
classic IFS node. The concept of wedge itself suffices to eliminate the redundancy implicit to replicating the
attributes for different corners of the same vertex with the same attributes, and does so in the most versatile
way possible. If slightly less versatile, the regions of IRS are more useful in practice since texture changes
usually happen along edges.
A region is unambiguously defined by specifying a connected subset of the mesh triangles, the vertices
included in that region being the ones that define the triangles in this subset. Only one attribute (e.g., one
(r, g, b) color triplet or one (u, v) pair of texture coordinates) may be specified for each vertex inside a given
region, but vertices sitting on region creases may have more attributes in their other region(s).
4.3.6.2 IndexedRegionSet node
4.3.6.2.1 Node interface
IndexedRegionSet {
eventIn MFInt32 set_colorIndex
eventIn MFInt32 set_coordIndex
eventIn MFInt32 set_normalIndex
eventIn MFInt32 set_texCoordIndex
exposedField SFNode color NULL
exposedField SFNode coord NULL
exposedField SFNode normal NULL
exposedField SFNode texCoord NULL
field SFBool ccw TRUE
field MFInt32 colorIndex [] # [-1,inf)
field SFBool colorPerVertex TRUE
field SFBool convex TRUE
field MFNode region []
field SFFloat creaseAngle 0 # [0,inf)
field MFInt32 normalIndex [] # [-1,inf)
field SFBool normalPerVertex TRUE
field SFBool solid TRUE
field MFInt32 texCoordIndex [] # [0,inf)
}
4.3.6.2.2 Functionality and semantics
An IRS node has exactly the same fields as an IFS one, except for coordIndex, which has been replaced by
region, meant to contain an array of Region nodes: faces originally described in the coordIndex field of the
classic IFS node need to be classified into regions.
4.3.6.3 Region node
4.3.6.3.1 Node interface
Region {
exposedField SFNode color NULL
exposedField SFNode normal NULL
exposedField SFNode texCoord NULL
exposedField SFNode texture NULL
exposedField SFNode textureTransform NULL
field MFInt32 colorIndex [] # [-1,inf)
field MFInt32 coordIndex [] # [-1,inf)
field MFInt32 normalIndex [] # [-1,inf)
field MFInt32 texCoordIndex [] # [0,inf)
}
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ISO/IEC 14496-16:2011/Amd.1:2011(E)
4.3.6.3.2 Functionality and semantics
Since vertices may be shared between regions whereas faces may not, the coord field may only exist (i.e., be
non-null) in the IRS node, while the coordIndex field may only exist (i.e., be non-empty) in the Region node.
As can be seen, the fields containing attributes or their corresponding indices coincide in the IRS and the
Region nodes. The way attributes are specified depends on whether these fields exist or not; and, if they do,
where they exist. There are two basic rules to avoid conflicts among them:
a) If one field exists inside the IRS node, its namesakes must not exist in any of its child Region nod
...
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