The two-dimensional rotation is done first, followed by the three-dimensional
rotation. That is, if R' is the rotational 2 x 2 matrix described by an angle,
and P is the 3 x 3 matrix projecting (0,0,1) to (xp,yp,zp), let R be
constructed from R' at the upper left sub-matrix, 1 at element 3,3 and zeros
elsewhere. Then the matrix formula for translating data is v' = P R v, where v
is the 3 x 1 vector of data extracted from the data file. In cases where the
data of the file is inherently not three-dimensional, logical rules are used to
place the data in three-space. (E.g., usually setting the z-dimension value to
zero and placing 2D data in the x-y plane.)