Re:How Quaternions encode rotations: derivation and sample code
by jordigh on Wednesday September 07, 2016 @06:32PM
(#12448519)
Okay, this makes a little more sense to me, since it's just the power series again. But I don't think that calling a rotation a growth makes sense. Also, to me, the approximation e^(i epsilon) ~ 1 + i epsilon kind of begs the question.
Re:How Quaternions encode rotations: derivation and sample code
by ThrustVectoring on Wednesday September 07, 2016 @07:09PM
(#12448805)
e^(epsilon) ~ 1 + epsilon in general, because of the definition of the derivative and the fact that d/dx (e^x) = e^x
Re:How Quaternions encode rotations: derivation and sample code
by jordigh on Wednesday September 07, 2016 @09:54PM
(#12449631)
Right, the latter fact is equivalent to considering exp the solution of a differential equation, which is a much bigger fact. Treating the approximation as an innocent brute fact is what I considered begging the question, because why should this differential equation be valid for complex values?
Re:How Quaternions encode rotations: derivation and sample code
by abecedarius on Wednesday September 07, 2016 @10:21PM
(#12449766)
I was trying to make a geometric intuition accessible to high schoolers who haven't mastered calculus -- though I haven't tried it on an actual teenager.
Of course there's also value in looking deeper into the foundations.
(I first got this picture from the Feynman lecture on algebra, http://www.feynmanlectures.caltech.edu/I_22.html, which doesn't seem to ever explain it that way explicitly. It's funny how memory works.)