NAME:	        ov_slice	

AUTHOR INFO:	David Parker, Stardent Computers, (617)-964-1000, email:davidp@stardent.com

TYPE:		mapper

INPUTS:		3D field (required)
		3D field 3 vector real (optional)

OUTPUTS:	Geom
                2D field

PARAMETERS:     Name		Type	Default		Min	Max
                ----            ----    -------         ---     ---
		read file	browser

		slice plane     int	    0	         0      255

		axis	        choice	    K	         I, J, K

		scale           dial       0.2          0.0     10.0 

		downsize        dial        1            1      16   

		arrows          boolean     0            0       1


DESCRIPTION:	
     The orthogonal vector slicer module takes	a 2D slice from	a 3D array of
     data values and a 3D array of vectors, overlaying the vector slice on the
     data slice as a hedgehog display. It does so by holding the array index 
     in one dimension constant, and letting the other indices vary. For instance,
     a data set might include a volume of 5000 points, arranged as follows 
     (using FORTRAN notation):

	  DATA(I,J,K)	 I = 1,10
			 J = 1,20
			 K = 1,25

     You can take a 2D "I-slice" from this data	set by setting I=4 and
     letting the other indices vary:

	  DATA(4,J,K)	 J = 1,20
			 K = 1,25

     The notation used in the example above assumes that the field's data
     values are	scalars	(in FORTRAN, DATA(4,5,6) must be a scalar).  If
     fact, however, the	orthogonal slicer module can takes slices of
     vector-valued fields, also.  It passes through whatever data type is
     presented to it; e.g. if the input	is a "field 3D 3-vector	float",	the
     output is a "field	2D 3-vector float".


READ FILE
  A browser which lets you specify the name of the ASCII input file.

SLICE PLANE 
  Determines the value of the array index to be	held constant.

AXIS
  Selects the dimension	(X, Y, or Z) in	which the array	index is to
  be held constant.

SCALE
  Scales the overlayed vectors.

DOWNSIZE
  Reduces the number of the vectors overlayed. A downsize value of two 
  specifies to display every other vector in both dimensions.  

ARROWS
  Selects the display of arrows instead of straight lines for vectors.


EXAMPLE: This is online as ov_slice.net. 


                                            READ FIELD
			         _______________|___________________
	                         |                     |           |
		         VECTOR GRADIENT               |           |
                                 |      _______________|           |
                                 |      |                          |
                                 |      |                          |
		     ORTHOGONAL VECTOR SLICER	                   |
				 |      |                          |
				 |      |                          |
	  GENERATE COLORMAP	 |      |__                        |
		  |_________	 |	  |                  VOLUME BOUNDS
			   |	 |        |		           |
			 FIELD TO MESH	  |                        |
			       |__________|	  _________________|
					  |	  |
				       RENDER GEOMETRY
					      |
				       DISPLAY PIXMAP



LIMITATIONS: currently, the module only handles irregular fields.