Upstream face_toward from Bevy

[alice-i-cecile]

As implemented here, this is a very convenient utility function that other users could benefit from.

Doing so would allow Bevy to deprecate our own implementation and avoid the extension trait.

[bitshifter]

As glam intends to be co-ordinate system agnostic it would need to be renamed face_toward_rh and a corresponding face_toward_lh should also be added.

Bevy switched from Mat4::look_at_rh to Mat4::face_toward in this commit bevyengine/bevy@3ee8aa8 but it's unclear to me why this change was made? How does this function differ from Mat4::look_at_rh? It looks like perhaps Mat4::face_toward is the same as Mat4::look_at_rh().inverse()? What is the benefit of one over the other for the purpose of documentation and explaining these methods to users?

[alice-i-cecile]

Hmm. That's a very good question. I'll ask around.

[alice-i-cecile]

Closing, per the discussion in bevyengine/bevy#3503