A grid is a data container that holds a value at every point in a
three dimensional lattice. The simplest type of value to hold is a
floating point value. In OEGrid, these are called
OEScalarGrids. OEScalarGrids are inherently cubic.
The following is the minimum amount of data needed to define a grid:
OESkewGrids are provided to represent grids with non-orthogonal axes.