For animation this kind of interpolation will be choppy and will be subject to gimbal lock when P1 and P2 X or Y axes point at eachother (you will get harsh sudden flipping at the halfway interpolation, try it out). Animation should use stuff like Quaternion Slerp. In Pufferfish the Tween Plane components use this (like Tween Through Planes) by having the Q (Quaternion) input true. You can see if that is faster for you and smoother animations in general. If so, you can check Rhinocommon’s Quaternion class and this thread response by Daniel Piker which has some good Quaternion info (specifically the QuaternionSpline.gh examples which are even better for animation smoothness).