CAN CSA-ISO IEC 14496-16A-2013 Information technology - Coding of audio-visual objects - Part 16 Animation Framework eXtension (AFX) AMENDMENT 1 Efficient representation of 3D mesh.pdf

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1、Information technology Coding of audio-visual objects Part 16: Animation Framework eXtension (AFX) AMENDMENT 1: Efficient representation of 3D meshes with multiple attributes Amendment 1:2013 (IDT) toNational Standard of CanadaCAN/CSA-ISO/IEC 14496-16:13(ISO/IEC 14496-16:2011, IDT)NOT FOR RESALE. /

2、PUBLICATION NON DESTINE LA REVENTE.Standards Update ServiceAmendment 1:2013 toCAN/CSA-ISO/IEC 14496-16:13January 2013Title:Information technology Coding of audio-visual objects Part 16: Animation Framework eXtension (AFX) AMENDMENT 1: Efficient representation of 3D meshes with multiple attributes Pa

3、gination:10 pages (iii preliminary and 7 text)To register for e-mail notification about any updates to this publicationgo to shop.csa.caclick on CSA Update ServiceThe List ID that you will need to register for updates to this publication is 2422254.If you require assistance, please e-mail techsuppor

4、tcsagroup.org or call 416-747-2233.Visit CSA Groups policy on privacy at csagroup.org/legal to find out how we protect your personal information.Reference numberISO/IEC 14496-16:2011/Amd.1:2011(E)ISO/IEC 2011INTERNATIONAL STANDARD ISO/IEC14496-16Fourth edition2011-11-01AMENDMENT 12011-12-01Informati

5、on technology Coding of audio-visual objects Part 16: Animation Framework eXtension (AFX) AMENDMENT 1: Efficient representation of 3D meshes with multiple attributes Technologies de linformation Codage des objets audiovisuels Partie 16: Extension du cadre danimation (AFX) AMENDEMENT 1: Reprsentation

6、 efficace de mailles 3D avec attributs multiples ISO/IEC 14496-16:2011/Amd.1:2011(E) COPYRIGHT PROTECTED DOCUMENT ISO/IEC 2011 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including p

7、hotocopying and microfilm, without permission in writing from either ISO at the address below or ISOs member body in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org ii ISO/IEC 20

8、11 All rights reservedAmendment 1:2013 to CAN/CSA-ISO/IEC 14496-16:13ISO/IEC 14496-16:2011/Amd.1:2011(E) ISO/IEC 2011 All rights reserved iiiForeword ISO (the International Organization for Standardization) and IEC (the International Electrotechnical Commission) form the specialized system for world

9、wide 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

10、 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 draf

11、ted 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 Inter

12、national 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. A

13、mendment 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. Amendment 1:2013 to CAN/CSA-ISO/IEC 14496-16:13Amendment 1:2013 to CAN/CSA-ISO/IEC 14496-16:13ISO/

14、IEC 14496-16:2011/Amd.1:2011(E) ISO/IEC 2011 All rights reserved 1Information 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 a

15、s 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 fa

16、ces 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 (on

17、e per mesh region) must be mapped. In this respect, IRS is somewhat related to the MultiTextureCoordinate 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 spe

18、cifying 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

19、 be achieved with IFS, thanks to its per corner mapping of attributes, but this would be less efficient from a bitstream size viewpoint. region 3 region 1 corner face vertex creaseregion 2 Figure Amd1.1 A vertex shared by three regions Figure Amd1.1 shows a triangle mesh vertex shared by eight trian

20、gles 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. Amendment 1:2013 to CAN/CSA-ISO

21、/IEC 14496-16:13ISO/IEC 14496-16:2011/Amd.1:2011(E) 2 ISO/IEC 2011 All rights reservedDefining 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 th

22、e 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 usefu

23、l 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 triple

24、t 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 eventI

25、n 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 SFBol ccw TRUE field MFInt32 colorIndex # -1,inf) field SFBool colorPerVert

26、ex TRUE field SFBool convex TRUE field MFNode region field SFFloat creaseAngle 0 # 0,inf) field MFInt32 normalIndex # -1,inf) field SFBool normalPerVertex TRUE field SFBol solid TRUE field MFInt32 texCoordIndex # 0,inf) 4.3.6.2.2 Functionality and semantics An IRS node has exactly the same fields as

27、 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 col

28、or 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) Amendmen

29、t 1:2013 to CAN/CSA-ISO/IEC 14496-16:13ISO/IEC 14496-16:2011/Amd.1:2011(E) ISO/IEC 2011 All rights reserved 34.3.6.3.2 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 coordIn

30、dex 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

31、. 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 nodes. b) If one field (except for textureTransform) exists inside one Region node, it must also exist in all its sibling Region nodes, and n

32、ot in its parent IRS node. Let us analyze, for instance, the possible combinations of the colorIndex fields for the color attribute, which are summarized in the following table, where we use the adjectives “public” to refer to fields of the IRS node and “private” for the ones of the Region nodes. co

33、lorIndex none one public many private colornone case N not allowed not allowed one public case PO case PI case RPI many private case RO not allowed case RI Case N: No colors are specified. Case PO: The color attribute does not follow the region division, and is applied once and only once to each ver

34、tex, regardless of the value of the colorPerVertex field. If there are n vertices in the coord field, then there shall be at least n colors in the color field. Case PI: The color attribute does not follow the region division, and is applied once and only once to each vertex, regardless of the value

35、of the colorPerVertex field. The colorIndex field shall contain at least as many indices as the number of vertices specified in coord. If the greatest index in colorIndex is n, then there shall be n+1 colors in the color field. For the rest of the cases, the colorPerVertex field has to be taken into

36、 account. Its value being FALSE means that attributes are specified on a per face basis. When its value is TRUE, each vertex has as many attributes as regions it belongs to, and the implicit order of the vertices belonging to a region, used while explaining the correspondence between them and their

37、attributes, is the one indicated by their position in coord. Case RPI: In each Region node there is a colorIndex field whose indices refer to the color field in the parent IRS node. If the greatest index in colorIndex is n, there shall be at least n+1 colors specified in the public color field. If c

38、olorPerVertex is TRUE (respectively, FALSE), colorIndex shall contain at least as many indices as the number of different vertices (resp. faces) that there are in the region. Case RO: In each Region node, one color from the local color field is assigned to each vertex or face of the region, dependin

39、g on the value of the colorPervertex field. If colorPerVertex is TRUE (resp. FALSE), color shall contain at least as many colors as the number of different vertices (resp. faces) that there are in the region. Case RI: In each Region node, the colorIndex field is used to assign each vertex a color fr

40、om the color field in that same Region node. If the greatest index in colorIndex is n, there shall be at least n+1 colors specified the color field of its region. If colorPerVertex is TRUE (resp. FALSE), colorIndex shall contain at least as many indices as the number of different vertices (resp. fac

41、es) that there are in the region. Amendment 1:2013 to CAN/CSA-ISO/IEC 14496-16:13ISO/IEC 14496-16:2011/Amd.1:2011(E) 4 ISO/IEC 2011 All rights reservedNormals are specified in exactly the same way as colors. For texture coordinates, however, there are some differences, the first being that the texCo

42、ordPerVertex field does not exist because it is assumed to always have the value TRUE. The texture and textureTransform fields in the Region node allow to specify different texture images for different regions, but the use of these fields is not mandatory. If texture coordinates are being specified

43、in an IRS node, the texture image used for nodes with a null texture field shall be the one specified in the appearance field of the Shape node that the IRS belongs to. The same goes for the textureTransform field. 4.3.6.4 Examples Figure Amd1.2 Two views of a cube with nine vertices and six faces a

44、nd texture regions The following examples represent the dice shown in Figure Amd1.2 by means of IRS nodes, demonstrating the versatility of the IRS concept. All of them use the case RPI for texture coordinates, and have no color or normal attributes. 4.3.6.4.1 First IRS example Figure Amd1.3 The six

45、 images to be mapped on the cube above in the first IRS example The first example uses the six images shown in Figure Amd1.3, one for each cube face. This results in six child Region nodes. Amendment 1:2013 to CAN/CSA-ISO/IEC 14496-16:13ISO/IEC 14496-16:2011/Amd.1:2011(E) ISO/IEC 2011 All rights res

46、erved 5Figure Amd1.4 Explanation of the texCoordIndex field for the first face/region of the first IRS example IndexedRegionSet coord Coordinate point 0 0 0, 1 0 0, 1 1 0, 0 1 0, 0 1 1, 0 0 1, 1 0 1, 1 1 1, 0.5 0.5 0 texCoord TextureCoordinate point 0 0, 1 0, 0 1, 1 1, 0.5 0.5 region Region coordInd

47、ex 2 1 8 -1, 1 0 8 -1, 0 3 8 -1, 3 2 8 texCoordIndex 3 1 0 2 4 texture ImageTexture url “/pix/1.png“ Region coordIndex 4 3 0 -1, 0 5 4 texCoordIndex 3 1 0 2 texture ImageTexture url “/pix/2.png“ Region coordIndex 6 5 0 -1, 0 1 6 texCoordIndex 3 2 1 0 texture ImageTexture url “/pix/3.png“ Region coor

48、dIndex 3 4 7 -1, 7 2 3 texCoordIndex 2 0 1 3 texture ImageTexture url “/pix/4.png“ Region coordIndex 1 2 7 -1, 7 6 1 texCoordIndex 0 1 2 3 texture ImageTexture url “/pix/5.png“ Region coordIndex 5 6 7 -1, 7 4 5 texCoordIndex 2 0 1 3 texture ImageTexture url “/pix/6.png“ 4.3.6.4.2 Second IRS example

49、The second example is based on the assumption that different texture images have to be used in different Region nodes, and that therefore the number of images to be wrapped around the cube can be decreased to two (shown in Figure Amd1.5), so that the IRS node can be encoded in a more compact way. Amendment 1:2013 to CAN/CSA-ISO/IEC 14496-16:13ISO/I