Dir Pter

tamte
your issues are stemming from the fact that the alembic interpolates deforming geometry linearly inbetween frames
so rotated geometry will distort a bit in-between frames, which in turn will result in slightly different best fit rigid transform than if the geo was not distorted
and since you are observing your timeline on fractional frames you see the issues like heartbeat scaling and misalignment (since you are comparing to transform that's using just rotation)

so if you don't want or can't export your alembic with transforming objects and have to use deforming geo, compute the Extract Transform only on integer frames and interpolate resulting transform after Extract Transform using TimeBlend SOP with Interpolate Rotation ... checked and maybe even Interpolation set to Cubic or Subdivision
(rather than keeping the linear Alembic interpolation of the geo before Extract Transform)

tamte
Thank you very much!!

tamte

444366454
Hi tamte.What I mean is that the imported model is an Alembic model with animations. There is no packedfulltransform for the ABC model. And I need to figure out the Angle of his rotation,

in that case you probably have deforming geo in your alembic and not transforming objects as they would still have "packedfulltransform" since Alembic can hold either

so as mentioned use Extract Transform before Transform Pieces to compute the actual transform difference between rest and current frame geo

I added a comment. It'll make you understand me better

tamte
here is a modified file with
- Transform pieces method
and
- if interested, custom VEX method to compute the transform matrix, but still using Transform By Attribute afterwards as that takes care of all cases of transformable geo and attributes, similar to Transform Pieces

since your objects are transforming after being packed and I assume your alembics contain transforming object this method should work
If however you had just deforming geo only then you would need Extract Transform on unpacked geo before connecting to transform pieces

Hi tamte.What I mean is that the imported model is an Alembic model with animations. There is no packedfulltransform for the ABC model. And I need to figure out the Angle of his rotation,