This table stores coordinates and indexes for cells in the MField table.
It allows one to translate between the PeanoHIlbert index (phkey) of a cell and its discrete cartesian coordinates (ix,iy,iz).
NOTE the (ix,iy,iz) coordinates have values in [1,256], not in [0,255]!
The motivation for this is that it makes it somewhat easier to deal with periodic boundary conditions when
querying for the neighbours of a cell identified by its phkey:
select s2.phkey
from mfield..spatial s1
, mfield..spatial s2
where s1.phkey=123456
and s1.ix between 0 and 255
and s1.iy between 0 and 255
and s1.iz between 0 and 255
and s2.ix between s1.ix1 and s1.ix+1
and s2.iy between s1.iy1 and s1.iy+1
and s2.iz between s1.iz1 and s1.iz+1
column  type  UCD  unit  description 
ix 
integer 
pos.cart.x 

The discrete x coordinate of the cell. Values between 1 and 256.

iy 
integer 
pos.cart.y 

The discrete y coordinate of the cell. Values between 1 and 256.

iz 
integer 
pos.cart.z 

The discrete z coordinate of the cell. Values between 1 and 256.

phkey 
integer 


The PeanoHilbert index of the cell. 
zindex 
integer 
time 

The bitinterleaving index of the cell. 
