double DLL_FUNC integrated_refraction( const double latitude,
const double observed_alt, const double wavelength_microns,
const double height_in_meters, const double rel_humid_pct,
const double temp_kelvins, const double pressure_mb)
{
const double g_bar = 9.784 * (1. - .0026 * cos( 2. * latitude)
- 2.8e-7 * height_in_meters); /* (3.281-4) */
const double Pw0 = rel_humid_pct * pow( temp_kelvins / 247.1, delta) / 100.;
const double l2 = wavelength_microns * wavelength_microns;
const double A = (273.15e-6 / 1013.25)
* (287.607 + 1.6288 / l2 + .0136 / (l2 * l2));
REFRACT ref;
double c5, rval;
LOCALS l0, lt, ls;
ref.r0 = re + height_in_meters;
ref.c2 = g_bar * Md / R;
ref.gamma = ref.c2 / alpha; /* = C3 */
c5 = Pw0 * (1. - Mw / Md) * ref.gamma / (delta - ref.gamma);
ref.c6 = A * (pressure_mb + c5) / temp_kelvins;
ref.c7 = (A * c5 + 11.2684e-6 * Pw0) / temp_kelvins;
ref.c8 = alpha * (ref.gamma - 1.) * ref.c6 / temp_kelvins;
ref.c9 = alpha * (delta - 1.) * ref.c7 / temp_kelvins;
ref.temp_0 = temp_kelvins;
l0.r = ref.r0;
compute_refractive_index( &ref, &l0, 1);
l0.z = PI / 2. - observed_alt;
compute_integrand( &l0);
lt.r = rt;
compute_refractive_index( &ref, <, 1);
lt.z = asin( l0.n * ref.r0 * sin( l0.z) / (lt.n * rt)); /* (3.281-9) */
compute_integrand( <);
ref.nt = lt.n;
ref.n0_r0_sin_z0 = l0.n * l0.r * sin( l0.z);
rval = total_refraction( &ref, &l0, <, 1, 0);
/* Now for the stratospheric portion... we need to recompute */
/* dn/dr at the tropopause, because there's a discontinuity */
/* in the derivative as r crosses that point; which also */
/* means we gotta recompute the integrand at r = rt. So: */
compute_refractive_index( &ref, <, 0);
compute_integrand( <);
ls.r = rs;
compute_refractive_index( &ref, &ls, 0);
ls.z = asin( ls.n * ref.r0 * sin( l0.z) / (ls.n * rs));
compute_integrand( &ls);
return( rval + total_refraction( &ref, <, &ls, 0, 0));
}
float LineEnergy::calc_energy() {
// The surface energy of a simple torus is the path integral of the square
// of the principal curvatures along the arm (as opposed to around it).
double energy = 0.0;
int numPoints = torus->getNumControlPoints();
double dt = 1.0/numPoints;
for (int v = 0; v < numPoints; v++) {
energy += compute_integrand(((double) v)/numPoints, dt);
}
double twist = torus->getGlobalTwist() * PI / 180;
energy += twist_weight * (twist*twist);
return (float) energy;
}
static double total_refraction( const REFRACT *ref,
const LOCALS *l1, const LOCALS *l2, const int is_troposphere,
const int recursion_depth)
{
LOCALS mid;
double change;
const double iteration_limit = 1.; /* get 'r' within a meter */
const double integration_tolerance = .0001;
const int max_recursion_depth = 20;
mid.z = (l1->z + l2->z) * .5;
mid.r = (l1->r + l2->r) * .5;
do
{
compute_refractive_index( ref, &mid, is_troposphere);
change = -(mid.n * mid.r - ref->n0_r0_sin_z0 / sin( mid.z));
change /= mid.n + mid.r * mid.dn_dr; /* (3.281-5) */
mid.r += change;
}
while( fabs( change) > iteration_limit);
compute_integrand( &mid);
/* Compute difference between a Simpson's rule integration */
/* and a trapezoidal one... */
change = 2. * mid.integrand - (l1->integrand + l2->integrand);
// if( recursion_depth >= max_recursion_depth)
// printf( "!!! recursed too deep\n");
/* ...and if it's too great, recurse with each half: */
if( fabs( change) > integration_tolerance && recursion_depth < max_recursion_depth)
return( total_refraction( ref, l1, &mid, is_troposphere, recursion_depth + 1)
+ total_refraction( ref, &mid, l2, is_troposphere, recursion_depth + 1));
else
{ /* Simpson's rule is good enough: */
const double h = (l2->z - l1->z) / 6.;
return( h * (4. * mid.integrand + l1->integrand + l2->integrand));
}
}
