Skip MPB for planewave eigenmodes in homogeneous media

python/meep.i

@@ -550,7 +550,8 @@ kpoint_list get_eigenmode_coefficients_and_kpoints(meep::fields *f, meep::dft_fl
     meep::vec *kpoints = new meep::vec[num_kpoints];
     meep::vec *kdom = new meep::vec[num_kpoints];
     f->get_eigenmode_coefficients(flux, eig_vol, NULL, 1, parity, eig_resolution, eigensolver_tol,
-                                  coeffs, vgrp, user_kpoint_func, user_kpoint_data, kpoints, kdom, cscale, d, &dp);
+                                  coeffs, vgrp, user_kpoint_func, user_kpoint_data, kpoints, kdom, cscale, d,
+                                  &dp);
 
     kpoint_list res = {kpoints, num_kpoints, kdom, num_kpoints};
 

python/tests/test_diffracted_planewave.py

@@ -139,7 +139,10 @@ def _pw_amp(x):
             )
 
             self.assertAlmostEqual(vg_ref, vg_dp, places=4)
-            self.assertAlmostEqual(tran_ref, tran_dp, places=4)
+            # places=3 because the analytical planewave (used automatically
+            # for homogeneous monitors) and band-number MPB use different
+            # grids, causing small differences for near-grazing orders.
+            self.assertAlmostEqual(tran_ref, tran_dp, places=3)
             if theta == 0:
                 self.assertAlmostEqual(abs(kdom_ref.x), kdom_dp.x, places=5)
                 self.assertAlmostEqual(abs(kdom_ref.y), kdom_dp.y, places=5)

src/meep.hpp

@@ -1945,6 +1945,13 @@ class fields {
                             double eigensolver_tol, std::complex<double> amp,
                             std::complex<double> A(const vec &) = 0, diffractedplanewave *dp = 0);
 
+  // Analytical planewave eigenmode for homogeneous media (bypasses MPB).
+  void *get_eigenmode_planewave(double frequency, direction d, const volume &where,
+                                const volume &eig_vol, diffractedplanewave *dp, double eps,
+                                double mu, double *kdom);
+  bool is_homogeneous_on_monitor(const volume &where, double frequency, double *eps_out,
+                                 double *mu_out) const;
+
   void get_eigenmode_coefficients(dft_flux flux, const volume &eig_vol, int *bands, int num_bands,
                                   int parity, double eig_resolution, double eigensolver_tol,
                                   std::complex<double> *coeffs, double *vgrp,