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# Optimal Rotational Axis For Spheres?

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### #1 Izzy

Izzy

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Posted 13 October 2012 - 03:35 AM

Related to my previous thread.

Imagine two points on the surface of a sphere, and you want to move Point A to Point B. Due to the nature of the problem, a single rotation suffices, as long as the new location of Point A is where Point B previously was. That is, the final orientation of the sphere is irrelevant, as long as that condition is met.

How do I find the rotation axis in order to use Rodrigues' Rotation Formula?

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### #2 phil1882

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Posted 14 October 2012 - 10:26 PM

Rodriguez rotation formula assumes you have a vector and rotation axis you want to rotate about.
what you currently have isn't sufficient to use that formula.
if you want to move point A to point B on a sphere through rotation, there are a lot of ways to do that.
here's one off the top of my head. plot a point C anywhere else on the sphere, find the plane that all three points a, b, and c lie on, find a line perpendicular to the plane that goes threw the center of the sphere, and rotate.
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