[X3D-Public] [x3dom-developers] initial X3D JSON conversion support using X3dToJson.xslt

[Don Brutzman]

More progress, on this version of a candidate encoding at least.

[...]
> To accomplish this means that the converter will need to be type-aware on a field-by-field basis when reading values.  When programming this, I'll need to trap booleans and strings first, then treat everything else as number.
>
> Will fix in next revision.

Stylesheet now removes default attribute values.  Also deduces typing based on content for boolean, number, number array, string, string array.

Strong typing will be a future modification - still needed since it is possible for numeric strings to sneak through as numbers despite using the prior heuristics.

> JSON question #1, wondering which is correct for a singleton number?
>
> 	"transparency": [1],
> or
> 	"transparency": 1,

Using second case.

> There are very few examples in the JSON spec.  A strict reading there seems to permit either form: an array with a single value, or else a singleton number with no surrounding brackets.
>
> JSON question #2, wondering which is correct for an MFVec3f value, single array or array of arrays?
>
> 	"keyValue": [0 0 0 1 1 1 2 2 2],
> or
> 	"keyValue": [ [0 0 0], [1 1 1], [2 2 2] ],

Revised candidates, with required commas:

	"keyValue": [ 0, 0, 0, 1, 1, 1, 2, 2, 2 ],
or
  	"keyValue": [ [0, 0, 0], [1, 1, 1], [2, 2, 2] ],

Still wondering.  This is likely a player question, what form is preferred for efficient operations.  Will assume the second form (array of arrays) unless someone argues otherwise.

Latest results maintained at

https://svn.code.sf.net/p/x3d/code/www.web3d.org/x3d/stylesheets/X3dToJson.xslt

https://svn.code.sf.net/p/x3d/code/www.web3d.org/x3d/stylesheets/test/HelloWorld.json
https://svn.code.sf.net/p/x3d/code/www.web3d.org/x3d/stylesheets/test/HelloWorld.scene.json

Still some problems with extra commas in the output, but cleaned-up version is attached to allow testing by anyone who wants to use JSON.parse() to read and generate objects.  It passes Netbeans/X3D-Edit JSON syntax testing.

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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{
  "#comment": "Example scene to illustrate X3D nodes and fields (XML elements and attributes)",
  "Group": [
  {
    "Viewpoint": {
      "@DEF": "ViewUpClose",
      "@centerOfRotation": [ 0, -1, 0 ],
      "@description": "Hello world!",
      "@position": [ 0, -1, 7 ]
    },
    "Transform": [
    {
      "@rotation": [ 0, 1, 0, 3 ],
      "Shape": [
      {
        "Sphere": {
        },
        "Appearance": [
        {
          "Material": {
            "@DEF": "MaterialLightBlue",
            "@diffuseColor": [ 0.1, 0.5, 1 ]
          },
          "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" ]
          }
        }
        ]
      }
      ]
    }
    ],
    "Transform": [
    {
      "@translation": [ 0, -2, 0 ],
      "Shape": [
      {
        "Text": [
        {
          "@DEF": "TextMessage",
          "@string": [ "Hello", "world!" ],
          "FontStyle": {
            "@justify": [ "MIDDLE", "MIDDLE" ]
          }
        }
        ],
        "Appearance": [
        {
          "Material": {
            "@USE": "MaterialLightBlue"
          }
        }
        ]
      }
      ]
    }
    ]
  }
  ]
}