blender Supporting smooth interpolation in Blender exporter

[FunFetched]

Hi there! I've been busy working on a modification to the Blender exporter and Babylon in an effort to support smooth interpolation natively, based on FCurve handles, as opposed to having to bake every frame of every animation prior to export, which can be rather time and space-consuming.

So far, I have a system which works fairly well, feeding the "right handle" offset of each keyframe to Babylon which then packs that information into the inTangent and outTangent properties of each imported keyframe. This has smoothed out my animations considerably, but it's not a 1:1 reproduction, and I feel like I could do more. inTangent and outTangent data is currently fed to Babylon's Hermite interpolation equation, which is certainly better than the Linear default, but still not as sweet as it would be if it used Bezier just as Blender does. Unfortunately, my Bezier kung-fu is weak, and making the translation from X/Y handle coordinates to Bezier coordinates for each axis is confusing me.

So, in summary, I'm now able to import the key and handle coordinates for each frame in Blender animations. I'm just having some trouble figuring out how to translate those into a contiguous Bezier curve at the time of animation. I'm familiar with the vector3InterpolateFunctionWithTangents() function, but inTangent and outTangent data doesn't seem to be enough for a full Bezier calculation. I could add more easily enough; I'm just a little fuzzy on how to go about it, and my experiments so far have resulted in some pretty crazy animations. Any thoughts? I would love to be able to wrap this up into a nice and tidy pull request.