what does the use_pca param means in SMPLH model?

[MagicSource]

Hello, may I ask what does the use_pca param means in SMPLH model?

[Yuri]

I found this:
hand_pose_dim = num_pca_comps if use_pca else 3 * self.NUM_HAND_JOINTS
https://github.com/vchoutas/smplx/blob/1265df7ba545e8b00f72e7c557c766e15c71632f/smplx/body_models.py#L641
I guess use_pca=False means we don't use the pca components to determine hand pose (like for body shape), rather we use the rotation vector to determine hand pose (like for body joints pose). But I'm not sure.
Maybe if I already have the rotation vectors for the joints(body, hand, ...), I should set use_pca=False.