Loads of lattice stuff

1 files changed, 34 insertions, 0 deletions

diff --git a/src/utils.c b/src/utils.c
index 38855671..fa239f90 100644
--- a/src/utils.c
+++ b/src/utils.c
@@ -122,3 +122,37 @@ int sign(double a)
 	if ( a > 0 ) return +1;
 	return 0;
 }
+
+
+void mapping_rotate(double x, double y, double z,
+                    double *ddx, double *ddy, double *ddz,
+                    double omega, double tilt)
+{
+	double nx, ny, nz;
+	double x_temp, y_temp, z_temp;
+
+	/* First: rotate image clockwise until tilt axis is aligned
+	 * horizontally. */
+	nx = x*cos(omega) + y*sin(omega);
+	ny = -x*sin(omega) + y*cos(omega);
+	nz = z;
+
+	/* Now, tilt about the x-axis ANTICLOCKWISE around +x, i.e. the
+	 * "wrong" way. This is because the crystal is rotated in the
+	 * experiment, not the Ewald sphere. */
+	x_temp = nx; y_temp = ny; z_temp = nz;
+	nx = x_temp;
+	ny = cos(tilt)*y_temp + sin(tilt)*z_temp;
+	nz = -sin(tilt)*y_temp + cos(tilt)*z_temp;
+
+	/* Finally, reverse the omega rotation to restore the location of the
+	 * image in 3D space */
+	x_temp = nx; y_temp = ny; z_temp = nz;
+	nx = x_temp*cos(-omega) + y_temp*sin(-omega);
+	ny = -x_temp*sin(-omega) + y_temp*cos(-omega);
+	nz = z_temp;
+
+	*ddx = nx;
+	*ddy = ny;
+	*ddz = nz;
+}