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                     ******* MODULE UPDATE - 05/19/92 ******
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AVS Modules						              trivar
Lawrence Berkeley Laboratory

NAME
     trivar - resample scattered data over two variables

SUMMARY
     Name	   trivar

     Type	   mapper

     Inputs	   field 1D irregular 3-coordinate scalar float

     Outputs	   field 2D irregular 3-coordinate scalar float

     Parameters	   
	Name		   Type		  Default	 Min	   Max
	xmin		   float	  -1.0		 unbounded
	xmax		   float	  1.0 		 unbounded
	ymin		   float	  -1.0 		 unbounded
	ymax		   float	  1.0		 unbounded
	zmin		   float	  -1.0 		 unbounded
	zmax		   float	  1.0		 unbounded
	xsamples	   integer	  20		 > 0
	ysamples	   integer	  20		 > 0
	zsamples	   integer	  20		 > 0
	search radius	   float	  1.0		 0.0	   "unbounded"
	weight function	   float	  1.0		 0.0	   100.0
	undefined value    float          -1.0           unbounded


DESCRIPTION
    The bivar module will resample 1d scatter data in 3 variables.  A
    typical use for this module is to take a field of 3-coordinate,
    scalar values, and resample over a "regular" grid.

    The algorithm used is one in which, for each output grid location,
    all input points are scanned to determine if they lie within the
    specified search radius.  If so, that input point's contribution
    is weighted as a function of distance from the output grid point
    and scaled by 1./distance**weightfunction.  As such, this module
    is best suited for use on input data which doesn't necessarily
    fit a diffentiable function.  For such data, refer to the scat3d
    module.

INPUTS

     Data Field	(required; field 1D irregular 3-coordinate scalar)
          The input field consists of a 1D field (scatter data) which
	  has scalar floating point data, and associated x,y,z
	  coordinate information.

PARAMETERS

     Xmin,Xmax,Ymin,Ymax,Zmin,Zmax
	The values of these variables define the coordinate range of
	the grid over which the input data will be resampled.  These
	values may be adjusted, for example, to form a bounding box
	around all the input data, or to look at a box enclosing
	some volume within the input data.

     Xsamples, Ysamples, Zsamples
	These values define the resolution of the resampling grid.
	Increasing these values will result in a "finer" grid,
	decreasing these values will result in a "coarser" grid
	(over the same coordinate range defined by Xmin,Xmax, etc.).

     Search Radius
	This floating point value sets the limit over which input
	scatter points will influence the value at a given output
	point.  Increasing this value will allow more points to 
        influence the value at a given output grid point, while
        decreasing this value will cause fewer points to be
        considered.

     Weight Function
	This floating point value is used to "weight" the contribution
	of a given input point to a given output value.  Increasing this
	value will lessen the contribution of input points "further
        away" than "closer" points at a given grid location.  In other
        words, points which are "closer" to a given grid location have
        significantly more influence than those further away.  Decreasing
        this value will increase the influence of points closer to the
        limits of the Search Radius.

     Undef Value
        This value is placed at those output grid locations in which no
        input values lie within the Search Radius.

OUTPUTS

	Field 2D irregular 3-coordinate scalar float
	   The output field is an "irregular" field consisting of
	   three data dimensions and two coordinate dimensions.
	   The data is a scalar floating point value.

EXAMPLE	1
	The first example illustrates the use of the bivar module
	to resample a scatter field, then display a 2-d slice as
        a scalar mesh.

	READ IRREGULAR   - where input data consists of 1D scattered data
             |
           TRIVAR
             |
      ORTHOGONAL SLICER
             |
       FIELD TO MESH
             |
        RENDER GEOMETRY
             |
        DISPLAY PIXMAP

RELATED MODULES
	bivar, scat2d, scat3d

AUTHOR
	Wes Bethel, Lawrence Berkeley Laboratory, 19 June 1991

AVS Modules						              trivar
Lawrence Berkeley Laboratory