Confused about setting rotations as 4D

[darthandvader]

Hi, very impressive work by you guys! One thing I'm a bit confused about is it mentions we can set the mean and scaling matrix in to 4 dimensional, which is very intuitive, but why you guys set the rotations into a pair of isotropic rotations? I'm just wondering why this process can relate different timestamps with the rotations from the original 3D gaussians. Thank you!

[KunruiHuang]

a rotation in 4D Euclidean space can be decomposed into a pair of isotropic rotations, each of which can be represented by a quaternion