1 files changed, 57 insertions, 0 deletions
diff --git a/src/ewald.c b/src/ewald.c
new file mode 100644
index 00000000..9d8a0450
--- /dev/null
+++ b/src/ewald.c
@@ -0,0 +1,57 @@
+/*
+ * 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 */
+	
+	k = 1/image->lambda;
+	
+	image->qvecs = malloc(image->width * image->height
+	                       * sizeof(struct threevec));
+	
+	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;
+		
+		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);
+		
+		image->qvecs[x + image->width*y].u = qx;
+		image->qvecs[x + image->width*y].v = qy;
+		image->qvecs[x + image->width*y].w = qz;
+	
+	}
+	}
+}