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// ************************************************************************* //
//                             avtSideVolume.h                               //
// ************************************************************************* //

#ifndef AVT_SIDE_VOLUME_H
#define AVT_SIDE_VOLUME_H


#include <avtSingleInputExpressionFilter.h>

class     vtkCell;


// ****************************************************************************
//  Class: avtSideVolume
//
//  Purpose:
//      Calculates all of the side volumes of the sides of a cell and then
//      assigns the side volume for the cell to be smallest.
//
//      A side volume is defined as the following:
//      A zone Z is comprised of edges, faces, and nodes.
//      Each face F has a center, C, where C is the linear average
//      of the nodes on F.
//      The center of Z is the linear average of the center of its
//      faces.
//      
//      Then there are two sides for each edge, E.
//      If edge E is made up of points V1 and V2 and E is incident
//      to faces F1 and F2, then one side is a tet consisting of
//      V1, V2, center(F1) and center(Z), where the other tet
//      consists of V1, V2, center(F2) and center(Z).
//      
//      The side volume expression returns either the smallest volume or the 
//      largest volume of the sides of a zone.  This is a little bit of 
//      laziness on our part, since the right thing to do would probably be to 
//      subdivide the mesh into tets and go from there.  But then there would 
//      be additional issues, and all of the customers agree this is a 
//      reasonable thing to do.
//
//  Programmer: Hank Childs
//  Creation:   January 20, 2005
//
//  Modifications:
//
//    Hank Childs, Thu Sep 22 15:39:11 PDT 2005
//    Add min and max variants.
//
//    Hank Childs, Wed May 21 15:55:53 PDT 2008
//    Re-define GetVariableDimension.
//
// ****************************************************************************

class EXPRESSION_API avtSideVolume : public avtSingleInputExpressionFilter
{
  public:
                                avtSideVolume();

    virtual const char         *GetType(void) { return "avtSideVolume"; };
    virtual const char         *GetDescription(void)
                                    { return "Calculating side volume"; };

    void                        SetTakeMin(bool tm) { takeMin = tm; };
    
  protected:
    bool                        haveIssuedWarning;
    bool                        takeMin;

    virtual vtkDataArray       *DeriveVariable(vtkDataSet *, int currentDomainsIndex);
    virtual void                PreExecute(void);

    virtual bool                IsPointVariable(void)  { return false; };
    virtual int                 GetVariableDimension()   { return 1; };

    double                      GetZoneVolume(vtkCell *);
};


#endif


