NAME
	add polar 2D - This module takes in a 2D field
	and adds coordinate data in (r,theta) spherical
	polar coordinates mapped to (x,y) cartesian as
	required by the geom_viewer. The added coordinates
	are either uniformly spaced or calculated from input
	coordinates, depending on whether the input field is
	uniform or rectilinear. Then, depending on what the
	original computational space grid was, the data
	can be mapped so that it covers the entire
	2*pi grid. 

SUMMARY
	Name	add polar 2D
	Type	Mapper
	Inputs	input_data - 	field 2D 3-space float REQUIRED

	Outputs	output_data - 	field 2D 2-space irregular float

	Parameters
	Name		Type	        Default	        Choices
	grid_theta	radio_buttons   (pi)		(pi/2,pi,2*pi)
	extend		toggle		(off)			

DESCRIPTION

	add polar 2D brings in a 2D field of either uniform or rectilinear
	type. The field is to have data that was calculated from
	a spherical polar mesh. If the input field is uniform,
	the field carries no coordinate information of its own
	and by default the coordinate mesh is assumed to be
	*UNIFORMLY* spaced. In this case, add polar 2D creates
	a new coordinate system in (x,y) from a simple
	mapping from the computational space grid to the
	geom_viewer's world grid which must be cartesian.
	
	If the input field is rectilinear, the field has
	an included coordinate array describing a 
	non-uniform grid, e.g. a graded mesh which
	is more dense along a symmetry axis than the
	region perpendicular to that axis. In such
	a case, the computed cartesian coordinates
	are found from the supplied spherical polar coordinates.

	The module also allows for mapping data to cover
	the full 2*pi radians found in the computational space grid.
	The user inputs what the size of the computational
	space grid was and whether or not the module
	should map to a full 2*pi.

	The module outputs an irregular field with spherical
	polar coordinate information mapped to cartesian
	coordinates that can be interpreted by modules
	such as field_to_mesh, etc.

	Note: this module assumes the input data is face (or cell) centered.

INPUTS
	input_data - field 2D 3-space float, either uniform or rectilinear 
        (input data is 3-space to be compatible with the Read_HDF module. users
         may want to change this for other read_data modules)

PARAMETERS

grid_theta (radio_buttons)
	
	-(pi/2, pi, 2*pi) Size of the ORIGINAL computational grid

extend (toggle)

	- whether to map data to full 2*pi radians if original
	grid < 2*pi.       

OUTPUTS
	output_data - field 2D 2-space irregular float

EXAMPLE NETWORKS

			____________
			|read field|
			------------
			     |
			--------------    -------------------
			|add polar 2D|    |generate colormap|
			--------------    -------------------
			     |                  |
			     |   ----------------
                             |   |
                        ----------------
			|field to mesh |
			----------------
                               |
                        ----------------
			|geom viewer   |
			----------------

RELATED MODULES

	read field, field_to_mesh, mesh_with_base, geometry_viewer