GLTF loader with Draco extension

[fanzhanggoogle]

(DO NOT Merge. It's for discussion only)

Hi @donmccurdy,

Thank you so much for the great work. We can discuss here for the detail.

@ondys
@FrankGalligan

[fanzhanggoogle]

In loadAccessors function, is it required to check if the accessor has bufferView before this line:
var arraybuffer = dependencies.bufferViews[ accessor.bufferView ];

[donmccurdy]

Makes sense; done. We may eventually need to consider what should be returned, since the accessor cannot create a THREE.BufferAttribute in this case.

[fanzhanggoogle]

From my understanding, bufferViews will be loaded when accessors are loaded. So the line is not necessary?

[donmccurdy]

Correct – bufferViews are a dependency of accessors, so they're already loaded, but must also be listed explicitly here for them to be included in the dependencies parameter.

[fanzhanggoogle]

According to the conformance, we need to use the version property to verify if the version of the encoded mesh and decoder are compatible, e.g. > 0.9.1.
@ondys
@FrankGalligan

[ondys]

one problem is that our draco_decoder.js currently does not provide API to query its version. I'll try to add that today.

Another thing is that we should most likely not care about the revision version, only the major and minor versions should affect the bitstream .. i.e. we should probably mention in the spec that for conformance, the decoder needs to support the major.minor version of the encoded file, revision can be ignored (if we want to include it at all).

[ondys]

Just a short update on the version (mostly for @donmccurdy) .. I'll probably land the CL internally later today, but an updated draco_decoder.js is most likely going to be available no earlier than Monday)

[donmccurdy]

Thanks @ondys! Let me know when the version is available, and get that check added.

[donmccurdy]

*and I'll get that check added.

[ondys]

@donmccurdy Thanks for the remainder! The version check should be available in our latest javascripts posted in our master branch. You can check whether the provided version is supported using function DracoModule.isVersionSupported(versionString)

The only problem is that the function needs to be called from and instance of DracoModule which is in your case automatically instantiated inside the class THREE.DRACOLoader and as far as I can tell, there is currently no easy way get the module out of the loader, so we may have to either add the version check functionality to THREE.DRACOLoader or we can make the DracoModule accessible to other classes. Alternatively, you can just create a new instance of DracoModule in your code, but that would be an overkill for a simple version check (it's actually quite costly to instantiate it).

[donmccurdy]

Great! Offhand I think exposing a isVersionSupported(version) method on THREE.DracoLoader, calling through to DracoModule, sounds like the way to go. I will try to look into that more this weekend. :)

[donmccurdy]

Just sent over a PR; avoiding making another DracoModule instance seems like a good call thanks.

[donmccurdy]

Any other issues we want to look into here? Once the version check is in, I think we could consider merging this to the three.js GLTF2Loader.

[donmccurdy]

I've updated this branch with the isVersionSupported check, and rebased against three.js/dev. (clean diff)