[Fiware-miwi] A Candidate AssetPipe: glTF aka. Collada JSON

[Tapani Jämsä]

Model updated to compressed version (Open3DGC). Binary size dropped from
23.2mb to 3.7mb. Viewer takes some time to initialize.

-Tapani


2013/11/27 Toni Alatalo <toni at playsign.net>

> The recommended asset pipeline is one of our main goals for the 3DUI now,
> https://forge.fi-ware.eu/plugins/mediawiki/wiki/fiware/index.php/FIWARE.Feature.MiWi.3D-UI.RecommendedAssetPipeline
>
> We have now studied and experimented with a candidate solution: glTF, the
> proposed gl Transfer Format by the Chronos group (creators of OpenGL, WebGL
> and COLLADA), http://www.khronos.org/gltf . Erno discovered it from
> SIGGRAPH proceedings I think.
>
> This is a quick preliminary heads-up of the activity — also to call for
> views / opinions about that tech if e.g. the DFKI folks already know
> whether it could be the solution for FI-WARE.
>
> The motivation for the new format and the associated complete pipeline is
> explained with a nice diagram in
> https://github.com/KhronosGroup/glTF/blob/master/specification/README.md .
> The idea is simple: use COLLADA to export from modeling tools and
> COLLADA2GLTF to convert it to the runtime format, optimized for transfers
> and easy loading. This way it covers all modeling apps without having to do
> anything in/with them (unlike the Three’s ‘native’ JSON export that we used
> in the first city rendering test). The scene/library format is similar to
> COLLADA but as JSON, with pointers to ready made byte array buffers in an
> external file with the geometry. Compressions such as CTM for geometry are
> planned to be supported as plugins.
>
> The spec is not finished yet and has been in fact living quite a lot
> during the past half a year. It is expected to be finished early next year.
> This is not a bad schedule for us as we can now verify whether it works for
> our needs now or does it need changes. We can also help with completing the
> work (e.g. loader(s)).
>
> Yesterday we finally got our test working: the old optimized 9 blocks city
> model, exported from Blender as COLLADA, shows with the raw WebGL glTF
> viewer: http://playsign.tklapp.com:8000/glTF-webgl-viewer/ (Oulu model is
> default but you can use the gui menu to switch to a few other models,
> bundled with the viewer project by glTF folks).
>
> This took a few days of intense testing and debugging. Main problem was
> incompatibilities with different versions of the glTF converter and the
> loaders: current converter is not compatible with any viewer we know :) ..
> this works by using a version from Nov ~5th, luckily the glTF files
> nowadays have the git hash of the version used so we could find this out
> from the example files that worked. Current test is with uncompressed data,
> we’ll test with compressed next (if it’s implemented in the loader). We
> also had problems with getting Blender export COLLADA correctly (texture /
> texcoord export settings).
>
> There is also a Three.js loader but so far it seems to work with the spec
> from about 5-6 months ago. We have not compiled that version of the
> converter yet to test and have not been able to load any own exports to
> Three. The guy working on the Three loader (Tony Parisi, one of the spec
> authors, author of a O’Reilly WebGL book and co-chair of the San Francisco
> WebGL meets) has worked on it a month ago to add shader loading support and
> animation / skinning loading earlier. I think we’ll test the Three loader
> soon again to see if can actually get animated models (e.g. avatars) over &
> animations working.
>
> So this is still early and definitely not conclusive. I am not surprised
> if we find out that the whole glTF idea based on COLLADA does not work.
> I’ve been evaluating COLLADA for soon 10 years and yet very rarely actually
> found it useful. But so far it looks that the time to jump to it could come
> now .. in 2014, in time for 10 year celebration of the 1.0 spec from 2004
> :) . Second Life and hence Opensimulator does happily rely on COLLADA only
> for getting meshes in (they have their own optimized LLMesh format for
> transfers then). There’s still way to go with the glTF pipeline so for now
> (probably for a month still) our recommendation for getting scenes simply
> from e.g. Blender to Three.js is the Three JSON format (used in the master
> branch of the city rendering repo & live demo), and CTM for an optimized
> solution (but it requires custom setup to set materials). Am very curious
> to hear what the DFKI gfx / XML3D folks think of this — some of you perhaps
> attended the SIGGRAPH sessions even?.
>
> Thanks to Tapani again for the valiant efforts in sorting all kinds of
> problems with getting started with this! Was a quite nice pair programming
> / battle we had..
>
> Cheers,
> ~Toni
>
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