[x3d-public] [x3dom-users] Ran across an interesting example.

Fri May 19 07:14:40 PDT 2017

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'/>

        <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
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