Convert Quaternion into a Rotation Matrix
The affine/rotation matrix R is calculated from the quaternion parameters.
quaternion2rotation(b, c, d, tol = 1e-07) quaternion2mat44(nim, tol = 1e-07)
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 |
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*a+b*b+c*c+d*d=1. The
(b,c,d) values are all that is needed, since we require that
a=sqrt(1.0-(b*b+c*c+d*d)) be non-negative.
The (b,c,d) values are stored in the (quatern_b,
quatern_c, quatern_d) fields.
The (proper) 3x3 rotation matrix or 4x4 affine matrix.
Brandon Whitcher bwhitcher@gmail.com
NIfTI-1
http://nifti.nimh.nih.gov/
## 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))
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