/**
* @param filename filename of the configuration file
* @param beamID beamID of the beam of interest (A=0, B=1, etc...)
*
* @return res The value of the y-offset of beamID computed at detector pixel p.
*/
float get_trace_yoff_at_pos(char *filename, int beamID, d_point p)
{
gsl_vector *v;
float n, c, res;
int i, j, k;
v = get_beam_trace_yoff(filename, beamID);
n = 0.5 * (-1.0 + sqrt(1 + 8 * v->size));
if ((floor(n) - n) != 0)
{
aXe_message(aXe_M_FATAL, __FILE__, __LINE__,
"get_trace_yoff_at_pos: "
"Beam %d in %s does not contain a correct number of entries (i.e. "
"1,3,6,10,15...,n^2/2+n/2", beamID, filename);
}
i = 0;
res = 0;
for (j = 0; j < n; j++)
{
for (k = 0; k < (j + 1); k++)
{
c = gsl_vector_get(v, i);
res = res + c * pow(p.x, (j - k)) * pow(p.y, k);
i++;
}
}
return res;
}
/**
* The function computes and stores at the according position
* the xy offsets of a direct image. This is only important
* in the fluxcube emission model, since the image coordinates
* in fluxcubes are 'filter' coordinates and do not take into
* account the offsets introduce by the grism.
* For each object and beam those offsets are evaluated
* and stored in the direct object structure.
*
* @param dirlist - the direct object
* @param CONF_file - the new coordinate point
*
*/
void fill_xy_offsets(dirobject **dirlist, char CONF_file[])
{
aperture_conf *conf;
gsl_vector *x_coeffs;
gsl_vector *y_coeffs;
d_point m_point;
double xoffs, yoffs;
int beamID=0;
int i;
// load the configuration file
conf = get_aperture_descriptor (CONF_file);
// go over each beam defined in the configuration
// file
for (beamID=0; beamID < conf->nbeams; beamID++)
{
// determine the coeeficients for the offsets
// in x and in y
x_coeffs = get_beam_trace_xoff (CONF_file, beamID);
y_coeffs = get_beam_trace_yoff (CONF_file, beamID);
// go over each direct object
i=0;
while (dirlist[i] !=NULL)
{
// get the mean direct object position
m_point = get_dirobject_meanpos(dirlist[i]);
// evaluate the coefficients for the 2D variable offsets
// at the mean position
dirlist[i]->xy_off[beamID].x = eval_trace_off_at_pos (x_coeffs, m_point, beamID);
dirlist[i]->xy_off[beamID].y = eval_trace_off_at_pos (y_coeffs, m_point, beamID);
// iterate the counter
i++;
}
// free the vectors for the coefficients
gsl_vector_free(x_coeffs);
gsl_vector_free(y_coeffs);
}
// release memory
free_aperture_conf(conf);
}