[x3d-public] [x3dom-users] Ran across an interesting example.
Leonard Daly
Leonard.Daly at realism.com
Fri May 19 07:30:01 PDT 2017
It is bad software practice to use flags in data streams. This was
standard practice decades ago because of the need to save memory. Now
more memory-used solutions are used to prevent the problem of
determining whether a value is a flag or real data. Of course, once the
data has been verified and loaded into memory, internal structures would
eliminate the need for flagging.
Leonard Daly
> Andreas,
>
> Thanks for your comments. Looking back at the standard again, that is
> ISO/IEC 19775-1 clause 13.3.6 IndexedFaceSet, notice what it says
> under list item e.1.:
>
> “If the /colorIndex/ field is not empty, 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 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 /X3DColorNode/ node.”
>
> In this case the end-of-face markers in /colorIndex/ are required to
> match the end-of-face markers in /coordIndex/. As we have already
> noted the /colorIndex/ rules also apply to /normalIndex/. Therefore,
> all three can have, in the right circumstances, -1 values. This is
> reflected in the node signature for each of these three fields.
>
> All the best,
>
> Roy
>
> *From:*Andreas Plesch [mailto:andreasplesch at gmail.com]
> *Sent:* 19 May 2017 14:35
> *To:* Roy Walmsley <roy.walmsley at ntlworld.com>
> *Cc:* John Carlson <yottzumm at gmail.com>; X3D Graphics public mailing
> list <x3d-public at web3d.org>; x3dom mlist
> <x3dom-users at lists.sourceforge.net>
> *Subject:* Re: [x3dom-users] [x3d-public] Ran across an interesting
> example.
>
> Hi Roy,
>
> sorry, I did not see your response in time.
>
> I do think the signatures for colorIndex and normalIndex should be
> corrected to not include "or -1". Currently, they state:
>
> MFInt32 [] colorIndex [] [0,∞) or -1
>
> MFInt32 [] normalIndex [] [0,∞) or -1
>
> Perhaps these were just copied from coordIndex ? Or did VRML allow the
> -1 ?
>
> On the other hand the signature for texCoordIndex is correct:
>
> MFInt32 [] texCoordIndex [] [-1,∞)
>
> -Andreas
>
> On Fri, May 19, 2017 at 6:24 AM, Roy Walmsley
> <roy.walmsley at ntlworld.com <mailto:roy.walmsley at ntlworld.com>> wrote:
>
> John,
>
> This is an interesting example, because technically it is not
> legal X3D !!
>
> That said, having saved it as a file, and tried it on the X3D
> Validator, it passed validation !!
>
> Your analysis is correct. Reviewing the standard explains why.
> Look at ISO/IEC 19775-1 clause 13.3.6 IndexedFaceSet
> (http://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/components/geometry3D.html#IndexedFaceSet).
>
> We’ll start with the eighth paragraph, which includes the words:
>
> “If the /normal/ field is not |NULL|, it shall contain a node
> derived from /X3DNormalNode/ 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/).”
>
> Now let’s look at what should happen for colorIndex when
> colorPerVertex is false. This is specified at list item d.1. two
> paragraphs earlier. It reads:
>
> “If the /colorIndex/ field is not empty, 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, there shall be N+1 colours in the /X3DColorNode/. The
> /colorIndex/ field shall not contain any negative entries.”
>
> Notice the last sentence, where it say there shall not be any
> negative values.
>
> So, applying these principles to the normals, we can see that
> there should be no negative values.
>
> Perhaps the Schematron could be improved by adding a rule to check
> for this scenario. And thinking about it, it would probably be
> possible to do it in JSON, although it would be complicated.
>
> All the best,
>
> Roy
>
> *From:*x3d-public [mailto:x3d-public-bounces at web3d.org
> <mailto:x3d-public-bounces at web3d.org>] *On Behalf Of *John Carlson
> *Sent:* 19 May 2017 10:57
> *To:* X3D Graphics public mailing list <x3d-public at web3d.org
> <mailto:x3d-public at web3d.org>>; x3dom-users at lists.sourceforge.net
> <mailto:x3dom-users at lists.sourceforge.net>
> *Subject:* [x3d-public] Ran across an interesting example.
>
> Below X3D XML NOT viewable in X3DOM, (Octaga??), Instant Player
> (console goes into infinite loop), H3D complains about: (Unnamed
> Normal.vector. Field has size 6). I think it may be because
> normalIndex has -1’s when normalPerVertex=false??? If I take out
> the -1’s, it’s viewable in X3DOM, Octaga, InstantPlayer, and H3D.
> The content still needs work, of course (It’s supposed to be a cube!).
>
> X3DOM’s console looks like:
>
> x3dom-full.js:4743 Uncaught TypeError: Cannot read property 'x' of
> undefined
>
> at x3dom.registerNodeType.defineClass.nodeChanged.nodeChanged
> (x3dom-full.js:4743)
>
> at x3dom.NodeNameSpace.setupTree (x3dom-full.js:2869)
>
> at x3dom-full.js:2869
>
> at Function.Array.forEach (x3dom-full.js:2)
>
> at x3dom.NodeNameSpace.setupTree (x3dom-full.js:2869)
>
> at x3dom-full.js:2869
>
> at Function.Array.forEach (x3dom-full.js:2)
>
> at x3dom.NodeNameSpace.setupTree (x3dom-full.js:2869)
>
> at x3dom-full.js:2869
>
> at Function.Array.forEach (x3dom-full.js:2)
>
> What does quality assurance report? I don’t get any significant
> warnings from X3D-Edit or X3DJSAIL, that I can tell!
>
> Not sure about the standard, but leaving out the -1’s makes sense
> if normalPerVertex = false, I think. I’ll let others weigh in
> about the standard.
>
> Thanks,
>
> John
>
> <?xml version="1.0" encoding="UTF-8"?>
>
> <!DOCTYPE X3D PUBLIC "ISO//Web3D//DTD X3D 3.3//EN"
> "http://www.web3d.org/specifications/x3d-3.3.dtd">
>
> <X3D profile='Interchange' version='3.3'
> xmlns:xsd='http://www.w3.org/2001/XMLSchema-instance'
> xsd:noNamespaceSchemaLocation='http://www.web3d.org/specifications/x3d-3.3.xsd'>
>
> <head>
>
> <meta name='title' content='template.json'/>
>
> <meta name='identifier'
> content='http://coderextreme.net/X3DJSONLD/template.json'/
> <http://coderextreme.net/X3DJSONLD/template.json%27/>>
>
> <meta name='description' content='Template for an Indexed
> Face Set'/>
>
> <meta name='creator' content='John Carlson'/>
>
> <meta name='created' content='4 April 2017'/>
>
> </head>
>
> <Scene>
>
> <Group>
>
> <Shape>
>
> <IndexedFaceSet DEF='IndexedFaceSet' colorIndex='0
> 0 0 -1 0 0 0 -1 0 0 0 0 -1 0 0 0 0 -1 0 0 0 0 -1 0 0 0 0 -1 0 0 0
> 0 -1' coordIndex='0 0 1 -1 0 1 1 -1 2 2 3 3 -1 0 3 3 0 -1 0 3 2 1
> -1 1 2 2 1 -1 1 2 3 0 -1' creaseAngle='1.57' normalIndex='0 -1 0
> -1 1 -1 2 -1 3 -1 4 -1 5 -1' normalPerVertex='false'>
>
> <Color color='0 1 0'/>
>
> <Coordinate point='0 0 1 0 1 1 1 1 1 1 0 1'/>
>
> <Normal vector='1 0 0 -1 0 0 0 1 0 0 0 -1 0 -1
> 0 0 0 1'/>
>
> </IndexedFaceSet>
>
> </Shape>
>
> </Group>
>
> </Scene>
>
> </X3D>
>
>
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>
> --
>
> Andreas Plesch
> 39 Barbara Rd.
> Waltham, MA 02453
>
>
>
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--
*Leonard Daly*
3D Systems & Cloud Consultant
LA ACM SIGGRAPH Chair
President, Daly Realism - /Creating the Future/
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