What is rigid align?

How do you obtain the rotation matrix?

What is reflection of a rotation matrix?

Is a reflection matrix a rotation matrix?

https://medium.com/machine-learning-world/linear-algebra-points-matching-with-svd-in-3d-space-2553173e8fed

Linear Algebra. Points matching with SVD in 3D space

https://igl.ethz.ch/projects/ARAP/svd_rot.pdf

https://www.quora.com/What-is-the-relationship-between-rotation-matrices-and-reflection-matrices#:~:text=A%20rotation%20matrix%20represents%20a,represent%20reflections%20in%20Euclidean%20space.