GLTF: Import step interpolation for loc/rot/scale as nearest

[demolke]

Currently all transform animation tracks get imported as linear.

To support things like camera cuts honor the interpolation mode set in the gltf.

[fire]

Note that GLTF cubic is not the same as godot cubic, so it will need to be baked or you can devise a curve fitting schema.

	} else if (gltf_interp == GLTFAnimation::INTERP_CUBIC_SPLINE) {
		return Animation::InterpolationType::INTERPOLATION_CUBIC;
	} else {
		return Animation::InterpolationType::INTERPOLATION_CUBIC;

[demolke]

Thanks a lot for taking a look - I should have been clearer, this is only about the STEP/NEAREST interpolation.

The method already does handle baking.

For STEP interpolation we do not want any in-betweens generated, so we have to mark the resulting animation track with NEAREST interpolation, the other tracks will get baked correctly.

I've made the change handle only the STEP case, wdyt?

[fire]

If you have some spare time, could check https://github.com/KhronosGroup/glTF-Sample-Models/tree/master/2.0/InterpolationTest

[demolke]

I think the change is working as it should. The existing code bakes everything to linear, so the only time we need to propagate the original interpolation intent is when it's STEP/NEAREST.

[aaronfranke]

Makes sense to me. We also have the same logic for weights a bit over 50 lines below here, so it makes sense to do this for pos/rot/scale tracks as well.

[akien-mga]

Thanks! And congrats for your first merged Godot contribution 🎉

[demolke]

Thank you