c4dynamics.rotmat.rotmat.rotx#

c4dynamics.rotmat.rotmat.rotx(phi)[source]#

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

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

$$\begin{array}{r}R=\left[\begin{array}{ccc}1& 0& 0\\ 0& cos(\phi )& sin(\phi )\\ 0& -sin(\phi )& cos(\phi )\end{array}\right]\end{array}$$

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]