3D Tiles support

[vpicavet]

The 3D Tiles specification is starting to take shape and approaches a stable version :

• https://github.com/AnalyticalGraphicsInc/3d-tiles

As the specification also enters OGC proposed work as community standard, it will be important to support this protocol at some point.

• https://www.gim-international.com/content/news/ogc-proposed-work-item-for-3d-tiles-as-community-standard

The spec will take the following parts into account for planned version 1.0 :

• tileset.json
• Batched 3D Model (b3dm)
• Instanced 3D Model (i3dm)
• Point Cloud (pnts)
• Vector Data
• Composite (cmpt)
• Declarative Styling

Cesium already implements the draft version of the specification :

• 3D Tiles Roadmap CesiumGS/cesium#3241

Some issues which must be solved before being able to implement 3D Tiles : 

• Vector data clamping Vector data clamping to ground #181 ( and related vector tiles support [loader] Vector tiles support #182 )
• Tile creation and update Tile creation and update #71
• gltf support in THREE.js

Do not hesitate to comment and add information on this large issue.

[Jeremy-Gaillard]

Working on it, starting with the tileset.json import.

[Jeremy-Gaillard]

tileset.json support:

• asset
  • version
  • tilesetVersion
  • gltfUpAxis
• bounding volume
  • box
  • region
  • sphere
• geometric error
• viewer request volume
• refine (add or replace)
• transform
• content
  • bounding volume
  • url
    • additional tileset.json are not supported Done
    • the url extension should be used to determine the tile type 3d-tiles specification has been updated to remove this constraint
• children

Known issues:

• the transformation matrix should apply to the box and sphere bounding volumes and viewer request volumes
• if a viewer request volume is defined, the loading of the content should be delayed until the camera is in the volume (currently, only the culling part is done)

[Jeremy-Gaillard]

Batched 3D Model (b3dm) support:

• Geometry
• Batch table
• Feature table

Additional issues:

• Three doesn't seem able to handle the batchId shader attribute

[vpicavet]

@NikoSaul is working on this issue

[qdnguyen]

What is he doing exactly? i'm also working on 3dtile generation, first test with 3d model of lyon.

[vpicavet]

Please consider contributing to https://github.com/Oslandia/py3dtiles/ if you want to work on the server-side aspects of 3D Tile : support for all the specs in the module and converter scripts are welcome.

@NikoSaul will start working on the client side, implementing 3D tiles support in iTowns, first with spec examples.

And please, please please, communicate before you start working on a subject, and try to consolidate / mutualize your efforts with existing projects.

[qdnguyen]

it's server-side that i'm doing now, but my objectif is to have a 3dtiles of Bati3D (paris, lyon) from cityGML format, so i used 3dcitydb and some javascript tools (ex. gltf to b3dm, 3dtile tool) to do that.