A transformation from one volume to another can act either in voxel
coordinates, world coordinates or a combination of both. In general,
voxel and world coordinates are related by a simple affine
transformation
, where
is the voxel
coordinate space, and
the world coordinate space. By using this
transformation, all transformations can be expressed as
transformations between world coordinates, which is more convenient
and will be assumed from here on.
For example, if
is a transformation between
two voxel coordinate spaces, then
is the
corresponding transformation between the world coordinate spaces.