c4dynamics.rotmat.rotmat.rotx

c4dynamics.rotmat.rotmat.rotx(phi)

Generate a 3x3 Direction Cosine Matrix for a positive rotation about the x-axis by an angle \(\phi\) in radians.

A right-hand rotation matrix about x is given by:

\[\begin{split}R = \begin{bmatrix} 1 & 0 & 0 \\ 0 & cos(\varphi) & sin(\varphi) \\ 0 & -sin(\varphi) & cos(\varphi) \end{bmatrix}\end{split}\]

Parameters:

phi (float or int) – The angle of rotation in radians.

Returns:

out (numpy.array) – A 3x3 rotation matrix representing the rotation about the x-axis.

Examples

>>> rotx(0)  
[[1  0  0]
 [0  1  0]
 [0  0  1]]

>>> rotx(c4d.pi / 2)  
[[1  0  0]
 [0  0  1]
 [0 -1  0]]

>>> v1 = [0, 0, 1]
>>> phi = 90 * c4d.d2r
>>> rotx(phi) @ v1 
[0  1  0]

>>> phi = 45 * c4d.d2r
>>> rotx(phi) @ v1 
[0  0.707  0.707]