Update rpkt.cc

rpkt.cc

@@ -816,10 +816,6 @@ __host__ __device__ void do_rpkt(Packet &pkt, const double t2) {
   while (true) {
     const auto nonemptymgi = grid::get_propcell_nonemptymgi(pkt.where);
 
-    // Assign optical depth to next physical event
-    const double zrand = rng_uniform_pos();
-    const double tau_next = -1. * log(zrand);
-
     // Start by finding the distance to the crossing of the grid cell
     // boundaries. sdist is the boundary distance and snext is the
     // grid cell into which we pass.
@@ -879,6 +875,8 @@ __host__ __device__ void do_rpkt(Packet &pkt, const double t2) {
     const double abort_dist = std::min(tdist, sdist);
 
     // Get distance to the next physical event (continuum or bound-bound)
+    const double zrand = rng_uniform_pos();
+    const double tau_next = -1. * log(zrand);
     double edist = -1;
     bool event_is_boundbound = true;
     const bool thickcell = (nonemptymgi >= 0) && (grid::modelgrid[nonemptymgi].thick == 1);