CUBIT example demonstrating how to use a field variable in an ExodusII
file to specify the cell size in a CUBIT mesh. This technique only
works for triangluar, quadrilateral, and tetrahedral cells.

Steps:

1. Generate a background mesh (ExodusII file) that will hold the field
variable (computed at the vertices) for the cell size. Create one
block so all sizing information is contained in a single block.

  Run the CUBIT journal file mesh_cellsize.jou.

2. Add the cell size field variable to the ExodusII file. In this case
we add two cell size variables, one based upon an analytical function
and one based upon a spatial database.

  Run the Python script exodus_add_properties.py.

3. Generate the CUBIT meshes using the cell size field variables.

  Run the CUBIT journal file mesh_size_spatialdb.jou and
  mesh_size_analyticfn.jou.

NOTES:

  The geometry in the background mesh used to specify the cell size
  *must* be exactly the same geometry as that of the final mesh. CUBIT
  will crash if the geometry is different.
