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/*
* ewald.c
*
* Calculate q-vector arrays
*
* (c) 2007-2009 Thomas White <thomas.white@desy.de>
*
* pattern_sim - Simulate diffraction patterns from small crystals
*
*/
#include <stdlib.h>
#include <math.h>
#include <stdio.h>
#include "image.h"
#include "utils.h"
#include "cell.h"
void get_ewald(struct image *image)
{
int x, y;
double k; /* Wavenumber */
double i0fac;
k = 1/image->lambda;
image->qvecs = malloc(image->width * image->height
* sizeof(struct threevec));
image->twotheta = malloc(image->width * image->height
* sizeof(double));
for ( x=0; x<image->width; x++ ) {
for ( y=0; y<image->height; y++ ) {
double rx, ry, r;
double twothetax, twothetay, twotheta;
double qx, qy, qz;
/* Calculate q vectors for Ewald sphere */
rx = ((double)x - image->x_centre) / image->resolution;
ry = ((double)y - image->y_centre) / image->resolution;
r = sqrt(pow(rx, 2.0) + pow(ry, 2.0));
twothetax = atan2(rx, image->camera_len);
twothetay = atan2(ry, image->camera_len);
twotheta = atan2(r, image->camera_len);
qx = k * sin(twothetax);
qy = k * sin(twothetay);
qz = k - k * cos(twotheta);
/* FIXME: Rotate vector here */
image->qvecs[x + image->width*y].u = qx;
image->qvecs[x + image->width*y].v = qy;
image->qvecs[x + image->width*y].w = qz;
image->twotheta[x + image->width*y] = twotheta;
}
}
}
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