[x3d-public] X3D JSON encoding: refactoring, simplifying handling of #comment and #ROUTE
clement at igonet.fr
clement at igonet.fr
Sat Dec 19 23:32:25 PST 2015
Oups, sorry, made a mistake, did not reply to the right mail/guy...
Le 20 décembre 2015 08:26:17 UTC+01:00, "clement at igonet.fr" <clement at igonet.fr> a écrit :
>Well... So, I used to use default coordinate system with meter as unit
>and center of the scene at level 0 as origin.
>Indeed, my conversion from default coordinate system to geo one can't
>work as is. I will provide again default system and fix my buggy and
>not tested geo X3D export.
>I've just updated Open Earth View wiki page with TODO notes.
>
>Thank you Don for having looked at such important details!
>
>Clément.
>
>Le 19 décembre 2015 22:09:18 UTC+01:00, Don Brutzman <brutzman at nps.edu>
>a écrit :
>>1. Am thinking about how we might improve the X3D JSON encoding by
>>treating #comment and #ROUTE as objects in an array that is contained
>>by parent. This would reduce problems with the partial resorting that
>>currently occurs.
>>
>>Doing it as part of "-children" isn't particularly difficult; the
>trick
>>will be doing it cleanly inside of nodes that contain other
>>non-children nodes, e.g. Shape, Appearance, singleton nodes, etc. The
>>path to success may lead through always treating any child content as
>>part of an array.
>>
>>Continuing this line of inquiry: we could put them inside of a
>>"-children" JSON field consistently throughout the scene graph. Use
>>cases:
>>a. Within "-children":[array] of Scene (which is already produced)
>>b. Within "-children":[array] of grouping nodes (which is already
>>produced)
>>c. Within "-children":[array] of any node, even when they don't have a
>>/children/ field
>>
>>2. So let's look at an example, in detail.
>>
>>Example scene created is named HelloWorldCommented.x3d with XML
>source,
>>current (original) JSON encoding, and alternative JSON encoding all
>>attached.
>>
>>First excerpt follows, with the focus just for regular children (use
>>cases 1.a and 1.b from above).
>>
>>=========================================
>>*XML encoding*
>>=========================================
>><X3D>
>> <Scene>
>><!-- Example scene to illustrate comments interspersed among X3D nodes
>>and fields (XML elements and attributes) -->
>> <!-- WorldInfo begin -->
>> <WorldInfo title='Hello world!'/>
>> <!-- WorldInfo complete, Group begin -->
>> <Group>
>> <!-- Viewpoint begin -->
>><Viewpoint DEF='ViewUpClose' centerOfRotation='0 -1 0'
>>description='Hello world!' position='0 -1 7'/>
>> <!-- Viewpoint complete, Transform begin -->
>> <Transform/>
>> <!-- Transform complete, Transform begin -->
>> <Transform/>
>> <!-- Transform complete -->
>> </Group>
>> <!-- Group complete -->
>> </Scene>
>></X3D>
>>=========================================
>>
>>Now two corresponding JSON examples using #comment attached. (Net
>>effect with #ROUTE would be the same.)
>>
>>Notice how comments are pulled up together in the current encoding
>>(which partially re-sorts and thus changes the original order), but
>>then comments are interspersed as expected in the second encoding:
>>=========================================
>>*current JSON encoding*
>>=========================================
>>{ "X3D": {
>> "Scene": {
>> "#comment":[
>>"Example scene to illustrate comments interspersed among X3D nodes and
>>fields (XML elements and attributes)",
>> "WorldInfo begin",
>> "WorldInfo complete, Group begin",
>> "Group complete"
>> ],
>> "-children":[
>> { "WorldInfo":
>> {
>> "@title":"Hello world!"
>> }
>> },
>> { "Group":
>> {
>> "#comment":[
>> "Viewpoint begin",
>> "Viewpoint complete, Transform begin",
>> "Transform complete, Transform begin",
>> "Transform complete"
>> ],
>> "-children":[
>> { "Viewpoint": { }
>> },
>> { "Transform": { }
>> },
>> { "Transform": { }
>> }
>> ]
>> }
>> }
>> ]
>> }
>> }
>>}
>>=========================================
>>*alternative JSON encoding*
>>=========================================
>>{ "X3D": {
>> "Scene": {
>> "-children":[
>>{ "#comment":"Example scene to illustrate comments interspersed among
>>X3D nodes and fields (XML elements and attributes)"},
>> { "#comment":"WorldInfo begin"},
>> { "WorldInfo":
>> {
>> "@title":"Hello world!"
>> }
>> },
>> { "#comment":"WorldInfo complete, Group begin"},
>> { "Group":
>> {
>> "-children":[
>> { "#comment":"Viewpoint begin"},
>> { "Viewpoint": { }
>> },
>> { "#comment":"Viewpoint complete, Transform begin"},
>> { "Transform": { }
>> },
>> { "#comment":"Transform complete, Transform begin"},
>> { "Transform": { }
>> },
>> { "#comment":"Transform complete"}
>> ]
>> }
>> },
>> { "#comment":"Group complete"}
>> ]
>> }
>> }
>>}
>>=========================================
>>
>>2. So far so good. Now let's look at how this approach ripples
>>through a Shape node, as an example of use case 1.c above.
>>
>>=========================================
>>*XML encoding*
>>=========================================
>><!-- Shape begin -->
>><Shape>
>> <!-- Text begin -->
>> <Text DEF='TextMessage' string='"Hello" "world!"'>
>> <!-- FontStyle begin -->
>> <FontStyle justify='"MIDDLE" "MIDDLE"'/>
>> <!-- FontStyle complete -->
>> </Text>
>> <!-- Text complete, Appearance begin -->
>> <Appearance>
>> <!-- Material begin -->
>> <Material USE='MaterialLightBlue'/>
>> <!-- Material complete -->
>> </Appearance>
>> <!-- Material complete -->
>></Shape>
>><!-- Shape complete -->
>>=========================================
>>
>>Once again the current/original X3D JSON encoding partially re-sorts
>>the comments:
>>=========================================
>>*current JSON encoding*
>>=========================================
>>"#comment":[
>>"Shape begin",
>>"Shape complete"
>>],
>>"-children":[
>> { "Shape":
>> {
>> "#comment":[
>> "Text begin",
>> "Text complete, Appearance begin",
>> "Material complete"
>> ],
>> "-geometry":[
>> { "Text":
>> {
>> "@DEF":"TextMessage",
>> "@string":["Hello","world!"],
>> "#comment":[
>> "FontStyle begin",
>> "FontStyle complete"
>> ],
>> "-fontStyle":[
>> { "FontStyle":
>> {
>> "@justify":["MIDDLE","MIDDLE"]
>> }
>> }
>> ]
>> }
>> }
>> ],
>> "-appearance":[
>> { "Appearance":
>> {
>> "#comment":[
>> "Material begin",
>> "Material complete"
>> ],
>> "-material":[
>> { "Material":
>> {
>> "@USE":"MaterialLightBlue"
>> }
>> }
>> ]
>> }
>> }
>> ]
>> }
>> }
>>]
>>=========================================
>>
>>And once again the alternative intersperses the comments as part of a
>>"-children" JSON key. Not so very different.
>>
>>Notable is that Shape and Appearance do not have /children/ fields,
>but
>>they do have child ("-children") comments. Thus scene graph structure
>>is better (though not perfectly) preserved.
>>
>>Some re-sorting of comments prior to peer nodes still appears to be
>>unavoidable, but it is reduced overall.
>>
>>The pattern for encoding comments (and ROUTEs) is fully consistent, so
>>parsing should still be straightforward.
>>=========================================
>>*alternative JSON encoding*
>>=========================================
>>"-children":[
>> { "#comment":"Shape begin"},
>> { "Shape":
>> {
>> "#comment":[
>> "Sphere begin",
>> "Sphere complete, Appearance begin",
>> "Appearance complete"
>> ],
>> "-geometry":[
>> { "Sphere":
>> {
>> }
>> }
>> ],
>> "-appearance":[
>> { "Appearance":
>> {
>> "-children":[
>> { "#comment":"Viewpoint begin"},
>> { "#comment":"Material begin"},
>> { "#comment":"Material complete, ImageTexture begin"},
>> { "#comment":"ImageTexture complete"}
>> ],
>> "-material":[
>> { "Material":
>> {
>> "@DEF":"MaterialLightBlue",
>> "@diffuseColor":[0.1,0.5,1]
>> }
>> }
>> ],
>> "-texture":[
>> { "ImageTexture":
>> {
>> "@DEF":"ImageCloudlessEarth",
>>"@url":["earth-topo.png","earth-topo.jpg","earth-topo-small.gif","http://www.web3d.org/x3d/content/examples/Basic/earth-topo.png","http://www.web3d.org/x3d/content/examples/Basic/earth-topo.jpg","http://www.web3d.org/x3d/content/examples/Basic/earth-topo-small.gif"]
>> }
>> }
>> ]
>> }
>> }
>> ]
>> }
>> },
>> { "#comment":"Shape complete"}
>>]
>>=========================================
>>
>>3. Analysis and next steps.
>>
>>I think that this alternative approach further reduces the
>special-case
>>handling of #comment and #ROUTE which exists in the current/original
>>JSON encoding.
>>
>>A more consistent JSON encoding simplifies parsing rules and hopefully
>>makes production/consumption easier to accomplish.
>>
>>Treating #comment and #ROUTE in the same fashion as other nodes,
>rather
>>than as field keys, also is more consistent with the primary design
>>pattern of the overall X3D JSON encoding.
>>
>>The alternative-encoding example was manually edited and validated
>>using jslint in X3D-Edit. If group review indicates that this
>approach
>>looks superior, I'll work on a refactoring of the X3dToJson.xslt
>>stylesheet and re-build all the examples to support continued in-depth
>>testing, implementation and evaluation.
>>
>>Thanks in advance for all scrutiny and review.
>>
>>all the best, Don
>>--
>>Don Brutzman Naval Postgraduate School, Code USW/Br
>>brutzman at nps.edu
>>Watkins 270, MOVES Institute, Monterey CA 93943-5000 USA
>>+1.831.656.2149
>>X3D graphics, virtual worlds, navy robotics
>>http://faculty.nps.edu/brutzman
>>
>>
>>------------------------------------------------------------------------
>>
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>>x3d-public mailing list
>>x3d-public at web3d.org
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>
>clement at igonet.fr
clement at igonet.fr
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