Rotation Matrix for Vector v=(a,b,c) by Angle θ | Efficient Computation Method

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Discussion Overview

The discussion revolves around finding an efficient method to compute the rotation matrix for a vector v=(a,b,c) by an angle θ. The focus is on exploring different approaches to derive the matrix, including the use of orthonormal bases and existing formulas.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant seeks a more efficient method than brute force for computing the rotation matrix from an orthonormal basis perpendicular to the vector v.
  • Another participant expresses skepticism about the existence of a simpler method than brute force.
  • A suggestion is made to research Rodrigues' rotation formula as a potential solution.
  • Another participant proposes using the orthonormal basis as a mapping to transform the usual orthonormal basis and suggests conjugating the rotation about the z-axis back to the desired axis.
  • A later reply provides a link to a post that describes how to construct the rotation matrix and what the expected result should be.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the most efficient method for computing the rotation matrix, with multiple competing views and approaches presented.

Contextual Notes

Some assumptions regarding the properties of the vector v and the definitions of the orthonormal basis may not be explicitly stated, and the discussion does not resolve the effectiveness of the proposed methods.

Silviu
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Hello! I need to find the rotation matrix around a given vector v=(a,b,c), by and angle ##\theta##. I can find an orthonormal basis of the plane perpendicular to v but how can I compute the matrix from this? I think I can do it by brute force, rewriting the orthonormal basis rotated by ##\theta## and doing some matrix multiplications, but is there a more clever and fast way to do it?
Thank you!
 
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I don't think there is any simpler method than "brute force".
 
You might want to research Rodrigues' rotation formula.
 
I guess this is what you are saying but the obviopus way to prceed seems to me to use the basis you have as a map sending the usual orthonormal basis to the new one, and use that map and its inverse to conjugate the (easily written) rotation about the z axis back to your axis.
 

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