G_utilities.3d {lattice}  R Documentation 
These are (related to) the default panel functions for cloud
and wireframe
.
ltransform3dMatrix(screen, R.mat)
ltransform3dto3d(x, R.mat, dist)
x 

screen 
list, as described in 
R.mat 
4x4 transformation matrix in homogeneous coordinates 
dist 
controls transformation to account for perspective viewing 
ltransform3dMatrix
and ltransform3dto3d
are utility
functions to help in computation of projections. These functions are
used inside the panel functions for cloud
and
wireframe
. They may be useful in userdefined panel functions
as well.
The first function takes a list of the form of the screen
argument in cloud
and wireframe
and a R.mat
, a
4x4 transformation matrix in homogeneous coordinates, to return a new
4x4 transformation matrix that is the result of applying R.mat
followed by the rotations in screen
. The second function
applies a 4x4 transformation matrix in homogeneous coordinates to a
3xn matrix representing points in 3D space, and optionally does some
perspective computations. (There has been no testing with nontrivial
transformation matrices, and my knowledge of the homogeneous
coordinate system is very limited, so there may be bugs here.)
Deepayan Sarkar Deepayan.Sarkar@Rproject.org