TrilinearInterpolation Class Reference

This class interpolates a function of three values (f(x,y,z)). More...

#include <TrilinearInterpolation.h>

Public Member Functions
	TrilinearInterpolation (const std::vector< Real > &x, const std::vector< Real > &y, const std::vector< Real > &z, const std::vector< Real > &data)
	Constructor initializes data for interpolation. More...
virtual	~TrilinearInterpolation ()=default
Real	sample (Real x, Real y, Real z) const
	Interpolates for the desired (x,y,z) coordinate and returns the value based on the function values vector. More...

Protected Member Functions
void	getCornerIndices (const std::vector< Real > &v, Real x, int &lower, int &upper, Real &d) const
	Finds the indices of the cube that point (x,y,z) is in. More...
Real	getCornerValues (int x, int y, int z) const
	Searches the function value vector for the value at a given corner coordinate from the getCornerIndices function. More...

Protected Attributes
std::vector< Real >	_x_axis
	vector of x-values More...
std::vector< Real >	_y_axis
	vector of y-values More...
std::vector< Real >	_z_axis
	vector of z-values More...
std::vector< Real >	_fxyz
	vector of function values, f(x,y,z) More...

Detailed Description

This class interpolates a function of three values (f(x,y,z)).

It takes 4 vectors for x, y, z, and function values, f(x,y,z). The vector of function values should be done in the following manner: Function values of constant x and y are written, corresponding with values in vector, z. Function values for the constant x, next y-value, corresponding with values in vector, z. After last y-value, function values for the next x, first y-value, corresponding with values in vector, z.

An example: f(1,4,7) = 10, f(1,4,8) = 11, f(1,4,9) = 12 f(1,5,7) = 13, f(1,5,8) = 14, f(1,5,9) = 15 f(1,6,7) = 16, f(1,6,8) = 17, f(1,6,9) = 18 f(2,4,7) = 20, f(2,4,8) = 21, f(2,4,9) = 22 f(2,5,7) = 23, f(2,5,8) = 24, f(2,5,9) = 25 f(2,6,7) = 26, f(2,6,8) = 27, f(2,6,9) = 28 f(3,4,7) = 30, f(3,4,8) = 31, f(3,4,9) = 32 f(3,5,7) = 33, f(3,5,8) = 34, f(3,5,9) = 35 f(3,6,7) = 36, f(3,6,8) = 37, f(3,6,9) = 38

x = {1, 2, 3}; y = {4, 5, 6}; z = {7, 8, 9}; fxyz = { // fxyz for x = 1 10, 11, 12, 13, 14, 15, 16, 17, 18, // fxyz for x = 2 20, 21, 22, 23, 24, 25, 26, 27, 28, // fxyz for x = 3 30, 31, 32, 33, 34, 35, 36, 37, 38 };

Definition at line 56 of file TrilinearInterpolation.h.

Constructor & Destructor Documentation

TrilinearInterpolation()

TrilinearInterpolation::TrilinearInterpolation	(	const std::vector< Real > &	x,
		const std::vector< Real > &	y,
		const std::vector< Real > &	z,
		const std::vector< Real > &	data
	)

Constructor initializes data for interpolation.

Parameters

x	vector for x-coordinates
y	vector for y-coordinates
z	vector for z-coordinates
data	vector for function values formatted in the same manner as the example

Definition at line 13 of file TrilinearInterpolation.C.

  : _x_axis(x), _y_axis(y), _z_axis(z), _fxyz(data)
{
  if (_x_axis.size() < 1)
    mooseError("x vector has zero elements. At least one element is required.");
  if (_y_axis.size() < 1)
    mooseError("y vector has zero elements. At least one element is required.");
  if (_z_axis.size() < 1)
    mooseError("z vector has zero elements. At least one element is required.");
  if (_x_axis.size() * _y_axis.size() * _z_axis.size() != data.size())
    mooseError("The size of data (",
               data.size(),
               ") does not match the supplied dimensions (",
               _x_axis.size(),
               ", ",
               _y_axis.size(),
               ", ",
               _z_axis.size(),
               ")");
}

~TrilinearInterpolation()

virtual TrilinearInterpolation::~TrilinearInterpolation ( )

virtualdefault

Member Function Documentation

getCornerIndices()

void TrilinearInterpolation::getCornerIndices ( const std::vector< Real > &  v, Real  x, int &  lower, int &  upper, Real &  d  ) const

protected

Finds the indices of the cube that point (x,y,z) is in.

Parameters

[in]	v	vector to find lower and upper limits for the cube
[in]	x	desired coordinate
[out]	lower	lower limit for cube
[out]	upper	upper limit for cube
[out]	d	ratio of (x - lower) / (upper - lower)

Definition at line 38 of file TrilinearInterpolation.C.

Referenced by sample().

{
  unsigned int N = v.size();
  if (x < v[0])
  {
    lower = 0;
    upper = 0;
  }
  else if (x >= v[N - 1])
  {
    lower = N - 1;
    upper = N - 1;
  }
  else
  {
    for (unsigned int i = 0; i < N - 1; i++)
    {
      if (x > v[i] && x < v[i + 1])
      {
        lower = i;
        upper = i + 1;
        d = (x - v[lower]) / (v[upper] - v[lower]);
        break;
      }
      else if (x == v[i])
      {
        lower = i;
        upper = i;
        break;
      }
    }
  }
}

getCornerValues()

Real TrilinearInterpolation::getCornerValues ( int  x, int  y, int  z  ) const

protected

Searches the function value vector for the value at a given corner coordinate from the getCornerIndices function.

Parameters

x	index for x-coordinate of corner
y	index for y-coordinate of corner
z	index for z-coordinate of corner

Returns

function value for the (x,y,z) coordinate

Definition at line 74 of file TrilinearInterpolation.C.

Referenced by sample().

{
  int nY = _y_axis.size();
  int nZ = _z_axis.size();

  return _fxyz[x * nY * nZ + y * nZ + z];
}

sample()

Real TrilinearInterpolation::sample	(	Real	x,
		Real	y,
		Real	z
	)		const

Interpolates for the desired (x,y,z) coordinate and returns the value based on the function values vector.

Parameters

x	desired x-coordinate
y	desired y-coordinate
z	desired z-coordinate

Returns

interpolated value at coordinate (x,y,z)

Definition at line 83 of file TrilinearInterpolation.C.

{
  int x0 = 0;
  int y0 = 0;
  int z0 = 0;
  int x1 = 0;
  int y1 = 0;
  int z1 = 0;
  Real Dx = 0;
  Real Dy = 0;
  Real Dz = 0;

  // find the the indices of the cube, which contains the point
  getCornerIndices(_x_axis, x, x0, x1, Dx);
  getCornerIndices(_y_axis, y, y0, y1, Dy);
  getCornerIndices(_z_axis, z, z0, z1, Dz);

  // find the corresponding function values for the corner indices
  Real f000 = getCornerValues(x0, y0, z0);
  Real f001 = getCornerValues(x0, y0, z1);
  Real f010 = getCornerValues(x0, y1, z0);
  Real f011 = getCornerValues(x0, y1, z1);
  Real f100 = getCornerValues(x1, y0, z0);
  Real f101 = getCornerValues(x1, y0, z1);
  Real f110 = getCornerValues(x1, y1, z0);
  Real f111 = getCornerValues(x1, y1, z1);

  // interpolation
  Real f00 = (f100 - f000) * Dx + f000;
  Real f10 = (f110 - f010) * Dx + f010;
  Real f01 = (f101 - f001) * Dx + f001;
  Real f11 = (f111 - f011) * Dx + f011;
  Real f0 = (f10 - f00) * Dy + f00;
  Real f1 = (f11 - f01) * Dy + f01;

  return (f1 - f0) * Dz + f0;
}

Member Data Documentation

_fxyz

std::vector<Real> TrilinearInterpolation::_fxyz

protected

vector of function values, f(x,y,z)

Definition at line 94 of file TrilinearInterpolation.h.

Referenced by getCornerValues().

_x_axis

std::vector<Real> TrilinearInterpolation::_x_axis

protected

vector of x-values

Definition at line 85 of file TrilinearInterpolation.h.

Referenced by sample(), and TrilinearInterpolation().

_y_axis

std::vector<Real> TrilinearInterpolation::_y_axis

protected

vector of y-values

Definition at line 88 of file TrilinearInterpolation.h.

Referenced by getCornerValues(), sample(), and TrilinearInterpolation().

_z_axis

std::vector<Real> TrilinearInterpolation::_z_axis

protected

vector of z-values

Definition at line 91 of file TrilinearInterpolation.h.

Referenced by getCornerValues(), sample(), and TrilinearInterpolation().

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The documentation for this class was generated from the following files:

• include/utils/TrilinearInterpolation.h
• src/utils/TrilinearInterpolation.C