PiecewiseInterp.h

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/*
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   Copyright (c) 2009 Scientific Computing and Imaging Institute,
   University of Utah.

   
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///
///@class PiecewiseInterp
///@brief Base class for local family of interpolation techniques
///
///@author 
///       Alexei Samsonov
///       Department of Computer Science
///       University of Utah
///  
///@date  July 2000
///


#ifndef SCI_PIECEWISEINTERP_H__
#define SCI_PIECEWISEINTERP_H__

#include <Core/Math/MiscMath.h>
#include <Core/Containers/Array1.h>
#include <sci_debug.h>

#include <iostream>

#if DEBUG
# define msg(m) std::cout << m << std::endl;
#else
# define msg(m)
#endif

namespace SCIRun {

template <class T> class PiecewiseInterp {
protected:
  bool data_valid;                // set to true in an interpolation specific cases
  int  curr_intrv;                // number of last interval used
  double min_bnd;            // and its boundaries (for camera path optimizations)
  double max_bnd; 
  Array1<double> points;          // sorted parameter points
  inline bool fill_data(const Array1<double>&);              

public:
  PiecewiseInterp() : data_valid(false), curr_intrv(-1), min_bnd(0), max_bnd(0) {}
  virtual ~PiecewiseInterp() {}
  inline int get_interval(double);

  virtual bool get_value(double, T&) = 0;
  virtual bool set_data(const Array1<double>& pts, const Array1<T>& vals) = 0;

  void reset() {
    data_valid = false;
    curr_intrv = -1;
    min_bnd = max_bnd = 0;
  }
};

// returns -1 if data is not valid or the value is out of boundaries
template <class T> inline int PiecewiseInterp<T>::get_interval(double w)
{
  if (data_valid) {
    if (w < min_bnd || w >= max_bnd) {  // taking advantage of smooth parameter changing    
      int lbnd = 0, rbnd = points.size()-1, delta = 0;
      
      if (w>=points[lbnd] && w<=points[rbnd]) {
        
        if (curr_intrv >= 0)
          if (w < min_bnd) {    // the series of optimizations that will take advantage
                              // on monotonic parameter changing (camera path interp.)      
            if (w >= points[curr_intrv - 1])
              lbnd=curr_intrv-1;            
            rbnd=curr_intrv;
            
          } else {
            if (w <= points[curr_intrv+1]) {
              rbnd = curr_intrv+1;
            }
            lbnd = curr_intrv;
          }
        
        while ((delta = rbnd - lbnd) != 1){
          if (w < points[lbnd + delta/2]) {
            rbnd = lbnd+delta/2;
          }
          else {
            lbnd += delta/2;
          }
        }
        
        curr_intrv = lbnd;
        min_bnd = points[curr_intrv];
        max_bnd = points[curr_intrv+1];
      }
      else
      {
        curr_intrv = (w < points[lbnd]) ? lbnd : rbnd;
        min_bnd = 0;
        max_bnd = 0;
      }
    }
  }
  else
    reset();
  
  return curr_intrv;
}
  
template<class T> inline bool PiecewiseInterp<T>::fill_data(const Array1<double>& pts){
  for (int i = 1; i < pts.size(); i++) {
    if ((pts[i] - pts[i-1]) < 1e-7) {
      return false;
    }
  } 

  points.resize(pts.size());
  points = pts;
  msg ("Filled!!!");
  return true;
}

} // End namespace SCIRun

#endif //SCI_INTERPOLATION_H__