JSON export bugfixes

[Floppy]

I was trying to debug my 3MF exporter using to_json, and found a few bugs that tripped it up. These changes fix those, so that running to_json on a loaded male02.obj file now works. No extra tests added, just a few quick tactical fixes that seem fairly obvious.

Incidentally, to_json in other contexts would normally produce a string, whereas this creates a hash which then needs JSON.generate() calling on it. Maybe something to reconsider down the line, what the "correct" output from to_json should be.

[Floppy]

The test failure here is because there is an extra level of object in the children array now. Rather than just containing objects, it contains complete to_json output from the child objects, including a metadata section. I'll update the code to pass, but I'm wondering, what should this be outputting? Should the metadata be in there? Or should it just be the contents of the "object" part of the child?

[Floppy]

Trying to phrase my question better. Which is the correct output?

{
  :metadata=>{
    :version=>4.3, 
    :type=>"Object", 
    :generator=>"ObjectExporter"
  }, 
  :object=>{
    :uuid=>"c52c90fd-8f3c-43ec-967f-4714b6a4a482", 
    :type=>"Object3D", 
    :matrix=>[1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0], 
    :children=>[
      {
        :uuid=>"cedd4b1e-e86d-4eb2-8591-314c5cec2e2a", 
        :type=>"Object3D", 
        :matrix=>[1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0]
      }
    ]
  }
}

or

{
  :metadata=>{
    :version=>4.3, 
    :type=>"Object", 
    :generator=>"ObjectExporter"
  }, 
  :object=>{
    :uuid=>"c52c90fd-8f3c-43ec-967f-4714b6a4a482", 
    :type=>"Object3D", 
    :matrix=>[1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0],
    :children=>[
      {
        :metadata=>{
          :version=>4.3, 
          :type=>"Object", 
          :generator=>"ObjectExporter"
        }, 
        :object=>{
          :uuid=>"cedd4b1e-e86d-4eb2-8591-314c5cec2e2a", 
          :type=>"Object3D", 
          :matrix=>[1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0]
        }
      }
    ]
  }
}

[danini-the-panini]

The first one, we don't need the metadata on every child object

[Floppy]

Great, thanks, I'll update the code :)

[Floppy]

@danini-the-panini To make sure this is right, I'm adding specific tests for mesh and line children, and I'm not sure if the behaviour I'm going for is correct.

Do ALL geometries and materials live in a single array at the root of the JSON, no matter the object nesting? Then the objects themselves reference them by UUIDs further down in the tree? So, the geometry and material for an object are NOT contained anywhere under the object/children array?

That's what it looks like it should be, from things like the Line and Mesh test_to_json tests, but I thought I'd check.

[danini-the-panini]

I think all the objects exist in the children array where they're nested

[Floppy]

Hm, interesting, in that case there would need to be another level in there, different to the current states. I think these two examples show the choice. The first one is in line with the current nesting method, whereas the second needs another level in there but is in line with existing mesh to_json output being wholly contained within the children array.

Sorry if this is confusing 😁

{
  geometries: [
    {
      uuid: "abc123",
      type: 'Geometry',
      data: {
        vertices: [],
        normals: [],
        faces: []
      }
    },
    {
      uuid: "bdc234",
      type: 'Geometry',
      data: {
        vertices: [],
        normals: [],
        faces: []
      }
    }
  ],
  materials: [
    {
      uuid: "def456",
      type: 'MeshBasicMaterial'
    },
    {
      uuid: "efg567",
      type: 'LineBasicMaterial'
    }
  ],
  object: {
    uuid: "c52c90fd-8f3c-43ec-967f-4714b6a4a482",
    type: "Object3D",
    children: [
      {
        uuid: "cedd4b1e-e86d-4eb2-8591-314c5cec2e2a",
        geometry: "abc123",
        material: "def456",
        type: "Mesh"
      },
      {
        uuid: "cedd4b1e-e86d-4eb2-8591-314c5cec2e2a",
        geometry: "bcd234",
        material: "efg567",
        type: "Line"
      }
    ]
  }
}

vs

{
  object: {
    uuid: "c52c90fd-8f3c-43ec-967f-4714b6a4a482",
    type: "Object3D",
    children: [
      {
        geometries: [
          {
            uuid: "abc123",
            type: 'Geometry',
            data: {
              vertices: [],
              normals: [],
              faces: []
            }
          }
        ],
        materials: [
          {
            uuid: "def456",
            type: 'MeshBasicMaterial'
          }
        ],
        object: {
          geometry: "abc123",
          uuid: "cedd4b1e-e86d-4eb2-8591-314c5cec2e2a",
          material: "def456",
          type: "Mesh"
        }
      },
      {
        geometries: [
          {
            uuid: "bdc234",
            type: 'Geometry',
            data: {
              vertices: [],
              normals: [],
              faces: []
            }
          }
        ],
        materials: [
          {
            uuid: "efg567",
            type: 'LineBasicMaterial'
          }
        ],
        object: {
          uuid: "cedd4b1e-e86d-4eb2-8591-314c5cec2e2a",
          geometry: "bcd234",
          material: "efg567",
          type: "Line"
        }
      }
    ]
  }
}

[danini-the-panini]

oh i see, i misunderstood.
yeah there should just be the top level materials and geometries, then the children objects just reference them by uuid.

[Floppy]

Great, thanks! It was a difficult question to phrase, no worries :)

[Floppy]

I'll revisit this once #125 is merged, to avoid conflicts.

[Floppy]

OK, this is good to go now. 🎉

Could merge before or after #125, I'll whichever goes in second.