Rotations: Difference between revisions

From David's Wiki
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* [https://docs.unity3d.com/ScriptReference/Quaternion.html Unity Quaternion Script Reference]
* [https://docs.unity3d.com/ScriptReference/Quaternion.html Unity Quaternion Script Reference]
* [https://threejs.org/docs/#api/en/math/Quaternion three.js Quaternion]
* [https://threejs.org/docs/#api/en/math/Quaternion three.js Quaternion]
** [https://github.com/mrdoob/three.js/blob/master/src/math/Quaternion.js three.js/Quaternion.js source code]
* [https://docs.scipy.org/doc/scipy/reference/generated/scipy.spatial.transform.Rotation.html scipy.spatial.transform.Rotation]
* [https://docs.scipy.org/doc/scipy/reference/generated/scipy.spatial.transform.Rotation.html scipy.spatial.transform.Rotation]


==References==
==References==

Revision as of 17:48, 19 May 2020

This article is about rotations in 3D space.

Representations

The most natural representation of rotations are Quaternions. However rotations can also be represented in various other forms.

Angle Axis

Rotation Vector

Euler Angles

Quaternion

Matrix

A \(3\times 3\) matrix is the most convenient form of a rotation since applying the rotation to a vector is simply a matrix multiplication.

Construction

This section is on converting between different forms of rotations.
How to construct a rotation.

Angle Axis to Matrix

Apply Wikipedia: Rodrigues' rotation formula

Suppose \(\mathbf{k}=(k_x, k_y, k_z)\) is the vector around which you want to rotate.
Let \[ \mathbf{K} = [\mathbf{k}]_\times = \begin{pmatrix} 0 & -k_z & k_y\\ k_z & 0 & -k_x\\ -k_y & k_x & 0 \end{pmatrix} \] Then our rotation matrix is: \[ \begin{equation} \mathbf{R} = \mathbf{I} + (\sin\theta)\mathbf{K} + (1-\cos\theta)\mathbf{K}^2 \end{equation} \]

Resources

References