DESCRIPTION:

Each volume has an associated array element within root.vol
that describes its state. It is accessed as root.vol[volumename]
where the volumename "current" is reserved and is an alias to the
currently active volume.
Each struct contains the following information elements:
- name (string) the name of the volume
- path (string) the name of the path the volume was loaded from
- size (intvector) the size of the volume in voxels.
- offset (vector) the offset of the volume relative to the
  global coordinate system.
- scale (vector) the scaling of the axis of the volume relative
  to the global coordinate system. Note that this is usually
  set up to allow for correct rendering of anisotropous data.
  Changing this value might distort the 3D images.
- turn.0/1/2 (vector) a 3x3 turn matrix used to translate between
  local and global coordinate system.