Matrices, quaternion and angle

Question

I have 2 matrices. Matrix A and Matrix B which is a 'matrix A rotated by some angle around some axis' (quaternion?). So: B = A.Transform (quaternion).
now when I know B and A, and maybe axis, how do I find the angle of that quaternion?

Sorry for bad text, I'm on a German keyboard and I'm not German...

For your keyboard, have you tried using Alt+Space? That will switch your keyboard to another language layout. — Sunny Patel
– Sunny Patel, Commented Apr 7, 2014 at 21:29

Chrisky · Accepted Answer · 2014-04-07 21:32:36Z

3

So you have B = A x T

therefore A^-1 x B = T

So take the matrix inverse of A and multiply that by B to get the Transform matrix.

Then extract the quaternion, (or Euler angles, if you would prefer), using say http://www.cg.info.hiroshima-cu.ac.jp/~miyazaki/knowledge/teche52.html

answered Apr 7, 2014 at 21:32

Chrisky

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2 Comments

apocalypse Over a year ago

Thanks, you saved my life. I converted result to System.Windows.Media.Media3D Qiaternion. Now I read Angle property from object. But I'm not sure, it will give me angle in range 0..180deg or 0..360deg?

Chrisky Over a year ago

I'm not sure either, but you can fix it up, e.g. angle = angle < 0.0 ? angle + 360 : angle; // to make it > 0

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