Support for time-based animations.

[AnBenLa]

Hello,
as I am new to this repository, I was wondering if it already supports the creation of USD animations.
Specifically, I'm interested in using keyframe transform data to create a USD file containing the animation.
Is this already supported in the current state of the project?

[syoyo]

Yes, timesampled attribute(animation) is supported in TinyUSDZ.

If you want to create a USD with animation attributes, see api-tutorial example

https://github.com/syoyo/tinyusdz/blob/469dbed09f43d5bf8a3396d2fa61c5ddae4aaea5/examples/api_tutorial/api-tutorial-main.cc#L125
(for xform ops)

and Animatable class for generic animatable Attribute(e.g. SkelAnimation.rotations https://github.com/syoyo/tinyusdz/blob/469dbed09f43d5bf8a3396d2fa61c5ddae4aaea5/src/usdSkel.hh#L250 )

https://github.com/syoyo/tinyusdz/blob/469dbed09f43d5bf8a3396d2fa61c5ddae4aaea5/src/prim-types.hh#L1106

As you may know, USD only supports Linear or Held(something like nearest_neighbor) interpolation, so need to convert slerp, cubic, etc keyframe to linear by oversampling keyframe samples. Codes in https://github.com/google/usd_from_gltf would help converting keyframe data for USD linear timesampled data.

[AnBenLa]

Thank you for the extensive reply and the note about oversampling keyframe samples!
For my use case, I settled for using time samples for the translation, rotation and scaling operations.

tinyusdz::XformOp translateOp;
translateOp.op_type = tinyusdz::XformOp::OpType::Translate;
translateOp.set_timesample(t0, pos0);
translateOp.set_timesample(t1, pos1);

[syoyo]

👍