stop rays at camera after reflection

Author: gridley

Diff for: src/plot.cpp

@@ -1713,6 +1713,14 @@ void PhongRay::on_intersection()
                  ? material()
                  : lowest_coord().cell;
 
+  // If we are reflected and have advanced beyond the camera,
+  // the ray is done. This is checked here because we should
+  // kill the ray even if the material is not opaque.
+  if (reflected_ && (r() - plot_.camera_position()).dot(u()) >= 0.0) {
+    stop();
+    return;
+  }
+
   // Anything that's not opaque has zero impact on the plot.
   if (!plot_.is_id_opaque(hit_id))
     return;