Shane Celis on Nostr: npub14yqjk…vrfl3 The direction of i, j, k defines the axis of rotation. And its ...

npub14yqjkzqkgv4a27egvq5xmh2ravemytg9g5kldqeqfts92uvh90sq2vrfl3 (npub14yq…rfl3) The direction of i, j, k defines the axis of rotation. And its magnitude relates to the angle of rotation θ by a factor of 1/sin(θ/2).

But why use half angles like θ/2? Because when you actually rotate a vector p with a quaternion q, you rotate it twice: p’ = q p q^-1