Output

quaternion2rotation

R Documentation

Convert Quaternion into a Rotation Matrix

Description

The affine/rotation matrix R is calculated from the quaternion parameters.

Usage

quaternion2rotation(b, c, d, tol = 1e-07)

quaternion2mat44(nim, tol = 1e-07)

Arguments

`b`	is the quaternion `b` parameter.
`c`	is the quaternion `c` parameter.
`d`	is the quaternion `d` parameter.
`tol`	is a very small value used to judge if a number is essentially zero.
`nim`	is an object of class `nifti`.

Details

The quaternion representation is chosen for its compactness in representing rotations. The orientation of the (x,y,z) axes relative to the (i,j,k) axes in 3D space is specified using a unit quaternion [a,b,c,d], where a^2+b^2+c^2+d^2=1. The (b,c,d) values are all that is needed, since we require that a=[1-(b^2+c^2+d^2)]^{1/2} be non-negative. The (b,c,d) values are stored in the (quatern_b, quatern_c, quatern_d) fields.

Value

The (proper) 3{\times}3 rotation matrix or 4{\times}4 affine matrix.

Author(s)

Brandon Whitcher bwhitcher@gmail.com

References

NIfTI-1
http://nifti.nimh.nih.gov/

Examples


## This R matrix is represented by quaternion [a,b,c,d] = [0,1,0,0]
## (which encodes a 180 degree rotation about the x-axis).
(R <- quaternion2rotation(1, 0, 0))

muschellij2/oro.nifti documentation built on Nov. 28, 2023, 5:36 a.m.