stop rays when exiting model

Author: gridley

src/plot.cpp

@@ -1659,6 +1659,13 @@ void Ray::trace()
       if (stop_)
         return;
 
+      // There are no more intersections to process
+      // if we hit the edge of the model, so stop
+      // the particle in that case:
+      if (dist_.distance == INFTY || dist_.distance == INFINITY) {
+        return;
+      }
+
       // Advance particle, prepare for next intersection
       for (int lev = 0; lev < n_coord(); ++lev) {
         coord(lev).r += dist_.distance * coord(lev).u;