TrilinearInterpolation.c File Reference

Compute coefficients for trilinear interpolation. More...

#include <mathfunctions.h>

Go to the source code of this file.

Functions
void	TrilinearInterpCoeffs (double xmin, double xmax, double ymin, double ymax, double zmin, double zmax, double x, double y, double z, double *coeffs)

Detailed Description

Compute coefficients for trilinear interpolation.

Author

Debojyoti Ghosh

Definition in file TrilinearInterpolation.c.

Function Documentation

TrilinearInterpCoeffs()

void TrilinearInterpCoeffs	(	double	xmin,
		double	xmax,
		double	ymin,
		double	ymax,
		double	zmin,
		double	zmax,
		double	x,
		double	y,
		double	z,
		double *	coeffs
	)

This function computes the coefficients for a trilinear interpolation at a given point (x,y,z) inside a cube defined by [xmin,xmax] X [ymin,ymax] X [zmin,zmax]. The coefficients are stored in an array of size 8 with each element corresponding to a corner of the cube in the following order:
coeffs[0] => xmin,ymin,zmin
coeffs[1] => xmax,ymin,zmin
coeffs[2] => xmin,ymax,zmin
coeffs[3] => xmax,ymax,zmin
coeffs[4] => xmin,ymin,zmax
coeffs[5] => xmax,ymin,zmax
coeffs[6] => xmin,ymax,zmax
coeffs[7] => xmax,ymax,zmax

Parameters

xmin	x-coordinate of the lower-end
xmax	x-coordinate of the higher-end
ymin	y-coordinate of the lower-end
ymax	y-coordinate of the higher-end
zmin	z-coordinate of the lower-end
zmax	z-coordinate of the higher-end
x	x-coordinate of the point to interpolate at
y	y-coordinate of the point to interpolate at
z	z-coordinate of the point to interpolate at
coeffs	array of size 8 (pre-allocated) to store the coefficients in

Definition at line 22 of file TrilinearInterpolation.c.

{
    double vol_inv = 1 / ((xmax-xmin)*(ymax-ymin)*(zmax-zmin));
    double tldx1 = x - xmin;
    double tldx2 = xmax - x;
    double tldy1 = y - ymin;
    double tldy2 = ymax - y;
    double tldz1 = z - zmin;
    double tldz2 = zmax - z;

    coeffs[0] = tldz2 * tldy2 * tldx2 * vol_inv;
    coeffs[1] = tldz2 * tldy2 * tldx1 * vol_inv;
    coeffs[2] = tldz2 * tldy1 * tldx2 * vol_inv;
    coeffs[3] = tldz2 * tldy1 * tldx1 * vol_inv;
    coeffs[4] = tldz1 * tldy2 * tldx2 * vol_inv;
    coeffs[5] = tldz1 * tldy2 * tldx1 * vol_inv;
    coeffs[6] = tldz1 * tldy1 * tldx2 * vol_inv;
    coeffs[7] = tldz1 * tldy1 * tldx1 * vol_inv;

    return;
}