DTVF: Additional properties in glTF nodes.

[mdhillman]

To enable compatability with the FeatureInfoAgent, the visualisation needs to be able to grab (at least) an iri and endpoint parameter from the object that Cesium returns upon the selection event firing.

Cesium makes this tricky as each type of input data has its own way of holding and getting this info. For glTF files within 3D tiles, I can see no obvious way to get this information.

I will need to look into the glTF standard to work out how to set this data in the first place, on a node-by-node level (so we have the flexibility of getting metadata on individual parts of a building), then ensuring it's propagated through Cesium's event system.

[mdhillman]

I'll use the glTF files I have for MK's house as a test case for this; see if I can add iri and endpoint parameters for different nodes (e.g. each walls chimney stack, the garage).

[mdhillman]

Looking at the glTF format, it appears that an extras object can be added to individual nodes within the file (details here).

A closed Cesium issue appears to suggest extra data is supported for each tileset, or each tile within a set. To select individual assets within a building say, we would need to ability to set extras on a per-node basis. Unfortunately, this does not appear to be supported by Cesium JS. I can find no pipeline to retrieve any per-node extra information from Cesium.

I can however get the name parameter for each node. One possibility is to escape a JSON object (containing whatever data we want) into a string and use that as the name for each node. The DTVF could then parse this to get the user-facing name, iri, endpoint etc. I'm not sure what software is used to create these glTF files, so setting this up may be tricky.

[mdhillman]

It looks like it may be possible to add additional parameters to the tileset JSON (rather than the glTF files themselves). I will test if this is accessible via Cesium.

This does however have the restriction that we can only set metadata (e.g. an iri) on a per-asset/tile basis.

[mdhillman]

It looks like it may be possible to add additional parameters to the tileset JSON (rather than the glTF files themselves). I will test if this is accessible via Cesium.

This does however have the restriction that we can only set metadata (e.g. an iri) on a per-asset/tile basis.

This is possible using the metadata/properties node within the tileset specification JSON. This will suffice for now, but it does mean that each asset (as defined in the tileset, not each node within the glTF) will be treated as a single entity with one iri.

[mdhillman]

Current implementation is sufficient for the foreseeable future.