Comments by "Liam" (@1495978707) on "Visualizing quaternions (4d numbers) with stereographic projection" video.

  1. I just wanted to say for other’s reference, one of the reasons for using quaternions is that gimbal lock isn’t a problem as with using rotation matrices and Euler angles. Plus, for a general 3D rotation, you have to do 27 products, and 27 additions. There’s a number of the terms that are zero, but hopefully you can see this way that quaternions are a much easier to use (if not understand way to handle rotations. I think it’s clear from Grants videos that quaternions amount to rotating a vector to a new point (3 degrees of freedom) and then specifying rotation about that axis (the fourth degree), instead of doing 3 Euler rotations, where each rotation depends on the last, and gimbal lock is an issue. It would be nice if Grant did a follow up explaining this stuff better than I am right now.
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