gltf::animation::Sampler and gltf::animation::Channel should have .index()

[schell]

First off - thanks for the great library!

I was expecting Sampler and Channel to have fn index(&self) -> usize that returns the index of the type in the Animation's samplers and channels fields, respectively.

That way we can easily associate a channel's sampler without resorting to constructing the channel's sampler and comparing against the animation's samplers.

Or maybe there's an easy way to do it that I'm missing? :)

[alteous]

Hi!

This looks like an oversight. We could add an index function for each for sure.

I worked with animations several years ago in three-rs. The code might be a useful reference:

https://github.com/three-rs/three/blob/master/src/factory/load_gltf.rs#L318