Animation id should refer to top-level animation, not sampler

[lasalvavida]

@RemiArnaud, could you take a look at this when you get a chance?

Currently the id of the animation object is created from the sampler, not the animation, so references (from animation clips, for example), are broken.

[lasalvavida]

Bump, I'd like to get KhronosGroup/COLLADA2GLTF#227 merged this week, and it is currently blocked by this.

[lasalvavida]

This should not be merged yet. I have been doing some work on automated validation in COLLADA2GLTF, and this causes some problems with models like VirtualCity who have multiple samplers within a single animation element, which is probably why the code was written this way originally.

This does still need to be fixed, but it's a little more complicated than just using the animation id. Animations are not samplers and the appropriate objects need to be added so that we can get the samplers belonging to an animation - accurately reflecting the structure of the COLLADA.

I have a temporary work-around for now on my end, and will update this with a more complete solution when I get a chance.