diff --git a/src/db/db/dbCompoundOperation.cc b/src/db/db/dbCompoundOperation.cc
index 29f1a37dd..d0d175149 100644
--- a/src/db/db/dbCompoundOperation.cc
+++ b/src/db/db/dbCompoundOperation.cc
@@ -1601,11 +1601,11 @@ CompoundRegionCheckOperationNode::do_compute_local (db::Layout *layout, const sh
 
   tl_assert (results.size () == 1);
   if (results.front ().empty ()) {
-    op.compute_local (layout, interactions, results, max_vertex_count, area_ratio);
+    op.do_compute_local (layout, interactions, results, max_vertex_count, area_ratio);
   } else {
     std::vector<std::unordered_set<db::EdgePair> > r;
     r.resize (1);
-    op.compute_local (layout, interactions, r, max_vertex_count, area_ratio);
+    op.do_compute_local (layout, interactions, r, max_vertex_count, area_ratio);
     results.front ().insert (r.front ().begin (), r.front ().end ());
   }
 }
@@ -1617,11 +1617,11 @@ CompoundRegionCheckOperationNode::do_compute_local (db::Layout *layout, const sh
 
   tl_assert (results.size () == 1);
   if (results.front ().empty ()) {
-    op.compute_local (layout, interactions, results, max_vertex_count, area_ratio);
+    op.do_compute_local (layout, interactions, results, max_vertex_count, area_ratio);
   } else {
     std::vector<std::unordered_set<db::EdgePair> > r;
     r.resize (1);
-    op.compute_local (layout, interactions, r, max_vertex_count, area_ratio);
+    op.do_compute_local (layout, interactions, r, max_vertex_count, area_ratio);
     results.front ().insert (r.front ().begin (), r.front ().end ());
   }
 }
diff --git a/src/db/db/dbCompoundOperation.h b/src/db/db/dbCompoundOperation.h
index 0d0563704..4f211a239 100644
--- a/src/db/db/dbCompoundOperation.h
+++ b/src/db/db/dbCompoundOperation.h
@@ -680,7 +680,11 @@ public:
   virtual ResultType result_type () const { return compound_operation_type_traits<TR>::type (); }
   virtual const db::TransformationReducer *vars () const  { return mp_vars; }
   virtual bool wants_variants () const { return m_wants_variants; }
-  virtual db::Coord computed_dist () const { return m_op->dist (); }
+
+  virtual db::Coord computed_dist () const
+  {
+    return CompoundRegionMultiInputOperationNode::computed_dist () + m_op->dist ();
+  }
 
   virtual std::vector<db::Region *> inputs () const
   {
diff --git a/src/db/db/dbLocalOperation.cc b/src/db/db/dbLocalOperation.cc
index 80b492460..c75205b1d 100644
--- a/src/db/db/dbLocalOperation.cc
+++ b/src/db/db/dbLocalOperation.cc
@@ -33,10 +33,74 @@
 #include "tlLog.h"
 #include "tlTimer.h"
 #include "tlInternational.h"
+#include "tlProgress.h"
 
 namespace db
 {
 
+// ---------------------------------------------------------------------------------------------
+//  local_operations implementation
+
+template <class TS, class TI, class TR>
+void local_operation<TS, TI, TR>::compute_local (db::Layout *layout, const shape_interactions<TS, TI> &interactions, std::vector<std::unordered_set<TR> > &results, size_t max_vertex_count, double area_ratio, bool report_progress, const std::string &progress_desc) const
+{
+  if (interactions.num_subjects () <= 1 || ! requests_single_subjects ()) {
+
+    do_compute_local (layout, interactions, results, max_vertex_count, area_ratio);
+
+  } else {
+
+    std::auto_ptr<tl::RelativeProgress> progress;
+    if (report_progress) {
+      progress.reset (new tl::RelativeProgress (progress_desc, interactions.size ()));
+    }
+
+    for (typename shape_interactions<TS, TI>::iterator i = interactions.begin (); i != interactions.end (); ++i) {
+
+      const TS &subject_shape = interactions.subject_shape (i->first);
+
+      shape_interactions<TS, TI> single_interactions;
+
+      if (on_empty_intruder_hint () == OnEmptyIntruderHint::Drop) {
+        single_interactions.add_subject_shape (i->first, subject_shape);
+      } else {
+        //  this includes the subject-without-intruder "interaction"
+        single_interactions.add_subject (i->first, subject_shape);
+      }
+
+      const std::vector<unsigned int> &intruders = interactions.intruders_for (i->first);
+      for (typename std::vector<unsigned int>::const_iterator ii = intruders.begin (); ii != intruders.end (); ++ii) {
+        const std::pair<unsigned int, TI> &is = interactions.intruder_shape (*ii);
+        single_interactions.add_intruder_shape (*ii, is.first, is.second);
+        single_interactions.add_interaction (i->first, *ii);
+      }
+
+      do_compute_local (layout, single_interactions, results, max_vertex_count, area_ratio);
+
+      if (progress.get ()) {
+        ++*progress;
+      }
+
+    }
+
+  }
+}
+
+
+//  explicit instantiations
+template class DB_PUBLIC local_operation<db::Polygon, db::Polygon, db::Polygon>;
+template class DB_PUBLIC local_operation<db::Polygon, db::Text, db::Polygon>;
+template class DB_PUBLIC local_operation<db::Polygon, db::Text, db::Text>;
+template class DB_PUBLIC local_operation<db::Polygon, db::Edge, db::Polygon>;
+template class DB_PUBLIC local_operation<db::Polygon, db::Edge, db::Edge>;
+template class DB_PUBLIC local_operation<db::PolygonRef, db::PolygonRef, db::PolygonRef>;
+template class DB_PUBLIC local_operation<db::PolygonRef, db::Edge, db::PolygonRef>;
+template class DB_PUBLIC local_operation<db::PolygonRef, db::PolygonRef, db::EdgePair>;
+template class DB_PUBLIC local_operation<db::Polygon, db::Polygon, db::EdgePair>;
+template class DB_PUBLIC local_operation<db::Edge, db::Edge, db::Edge>;
+template class DB_PUBLIC local_operation<db::Edge, db::PolygonRef, db::Edge>;
+template class DB_PUBLIC local_operation<db::Edge, db::Edge, db::EdgePair>;
+
 // ---------------------------------------------------------------------------------------------
 //  BoolAndOrNotLocalOperation implementation
 
diff --git a/src/db/db/dbLocalOperation.h b/src/db/db/dbLocalOperation.h
index eb488bede..abf6b4165 100644
--- a/src/db/db/dbLocalOperation.h
+++ b/src/db/db/dbLocalOperation.h
@@ -29,8 +29,6 @@
 
 #include "dbLayout.h"
 #include "dbEdgeBoolean.h"
-#include "tlProgress.h"
-#include "tlInternational.h"
 
 #include <unordered_map>
 #include <unordered_set>
@@ -89,55 +87,10 @@ public:
 
   /**
    *  @brief Computes the results from a given set of interacting shapes
-   *  @param layout The layout to which the shapes belong
-   *  @param interactions The interaction set
-   *  @param result The container to which the results are written
    *
    *  If the operation requests single subject mode, the interactions will be split into single subject/intruder clusters
    */
-  void compute_local (db::Layout *layout, const shape_interactions<TS, TI> &interactions, std::vector<std::unordered_set<TR> > &results, size_t max_vertex_count, double area_ratio, bool report_progress = false, const std::string &progress_desc = std::string ()) const
-  {
-    if (interactions.num_subjects () <= 1 || ! requests_single_subjects ()) {
-
-      do_compute_local (layout, interactions, results, max_vertex_count, area_ratio);
-
-    } else {
-
-      std::auto_ptr<tl::RelativeProgress> progress;
-      if (report_progress) {
-        progress.reset (new tl::RelativeProgress (progress_desc, interactions.size ()));
-      }
-
-      for (typename shape_interactions<TS, TI>::iterator i = interactions.begin (); i != interactions.end (); ++i) {
-
-        const TS &subject_shape = interactions.subject_shape (i->first);
-
-        shape_interactions<TS, TI> single_interactions;
-
-        if (on_empty_intruder_hint () == OnEmptyIntruderHint::Drop) {
-          single_interactions.add_subject_shape (i->first, subject_shape);
-        } else {
-          //  this includes the subject-without-intruder "interaction"
-          single_interactions.add_subject (i->first, subject_shape);
-        }
-
-        const std::vector<unsigned int> &intruders = interactions.intruders_for (i->first);
-        for (typename std::vector<unsigned int>::const_iterator ii = intruders.begin (); ii != intruders.end (); ++ii) {
-          const std::pair<unsigned int, TI> &is = interactions.intruder_shape (*ii);
-          single_interactions.add_intruder_shape (*ii, is.first, is.second);
-          single_interactions.add_interaction (i->first, *ii);
-        }
-
-        do_compute_local (layout, single_interactions, results, max_vertex_count, area_ratio);
-
-        if (progress.get ()) {
-          ++*progress;
-        }
-
-      }
-
-    }
-  }
+  void compute_local (db::Layout *layout, const shape_interactions<TS, TI> &interactions, std::vector<std::unordered_set<TR> > &results, size_t max_vertex_count, double area_ratio, bool report_progress = false, const std::string &progress_desc = std::string ()) const;
 
   /**
    *  @brief Indicates the desired behaviour when a shape does not have an intruder
diff --git a/src/db/db/dbRegionLocalOperations.cc b/src/db/db/dbRegionLocalOperations.cc
index 1ffb85f74..24307a99b 100644
--- a/src/db/db/dbRegionLocalOperations.cc
+++ b/src/db/db/dbRegionLocalOperations.cc
@@ -200,9 +200,9 @@ void
 check_local_operation<TS, TI>::do_compute_local (db::Layout *layout, const shape_interactions<TS, TI> &interactions, std::vector<std::unordered_set<db::EdgePair> > &results, size_t /*max_vertex_count*/, double /*area_ratio*/) const
 {
   tl_assert (results.size () == 1);
-  std::unordered_set<db::EdgePair> result;
+  std::unordered_set<db::EdgePair> result, intra_polygon_result;
 
-  edge2edge_check_negative_or_positive<std::unordered_set<db::EdgePair> > edge_check (m_check, result, m_options.negative, true, true, m_options.shielded);
+  edge2edge_check_negative_or_positive<std::unordered_set<db::EdgePair> > edge_check (m_check, result, intra_polygon_result, m_options.negative, m_different_polygons, m_has_other, m_options.shielded);
   poly2poly_check<TS> poly_check (edge_check);
 
   std::list<TS> heap;
@@ -302,30 +302,6 @@ check_local_operation<TS, TI>::do_compute_local (db::Layout *layout, const shape
     scanner.process (poly_check, m_check.distance (), db::box_convert<TS> ());
   } while (edge_check.prepare_next_pass ());
 
-  //  now also handle the intra-polygon interactions if required
-
-  std::unordered_set<db::EdgePair> intra_polygon_result;
-
-  if (! m_different_polygons && ! m_has_other) {
-
-    for (typename shape_interactions<TS, TI>::iterator i = interactions.begin (); i != interactions.end (); ++i) {
-
-      std::list<TS> heap;
-
-      const TS &subject = interactions.subject_shape (i->first);
-      scanner.clear ();
-      scanner.insert (push_polygon_to_heap (layout, subject, heap), 0);
-
-      edge2edge_check_negative_or_positive<std::unordered_set<db::EdgePair> > edge_check_intra (m_check, intra_polygon_result, m_options.negative, false, false, m_options.shielded);
-      poly2poly_check<TS> poly_check_intra (edge_check_intra);
-
-      do {
-        scanner.process (poly_check_intra, m_check.distance (), db::box_convert<TS> ());
-      } while (edge_check_intra.prepare_next_pass ());
-
-    }
-
-  }
 
   //  detect and remove parts of the result which have or do not have results "opposite"
   //  ("opposite" is defined by the projection of edges "through" the subject shape)
@@ -497,18 +473,13 @@ check_local_operation<TS, TI>::do_compute_local (db::Layout *layout, const shape
       for (std::unordered_set<db::EdgePair>::const_iterator i = result.begin (); i != result.end (); ++i) {
         results.front ().insert (db::EdgePair (i->first (), i->first ().swapped_points ()));
       }
-
-    } else {
-
-      results.front ().insert (result.begin (), result.end ());
+      result.clear ();
 
     }
 
-  } else {
-
-    results.front ().insert (result.begin (), result.end ());
-
   }
+
+  results.front ().insert (result.begin (), result.end ());
 }
 
 template <class TS, class TI>
diff --git a/src/db/db/dbRegionLocalOperations.h b/src/db/db/dbRegionLocalOperations.h
index 73da44aad..2b3977c25 100644
--- a/src/db/db/dbRegionLocalOperations.h
+++ b/src/db/db/dbRegionLocalOperations.h
@@ -210,14 +210,14 @@ public:
   virtual bool requests_single_subjects () const { return true; }
   virtual std::string description () const;
 
+  virtual void do_compute_local (db::Layout * /*layout*/, const shape_interactions<TS, TI> &interactions, std::vector<std::unordered_set<db::EdgePair> > &results, size_t /*max_vertex_count*/, double /*area_ratio*/) const;
+
 private:
   EdgeRelationFilter m_check;
   bool m_different_polygons;
   bool m_has_other;
   bool m_other_is_merged;
   db::RegionCheckOptions m_options;
-
-  virtual void do_compute_local (db::Layout * /*layout*/, const shape_interactions<TS, TI> &interactions, std::vector<std::unordered_set<db::EdgePair> > &results, size_t /*max_vertex_count*/, double /*area_ratio*/) const;
 };
 
 typedef check_local_operation<db::PolygonRef, db::PolygonRef> CheckLocalOperation;
diff --git a/src/db/db/dbRegionUtils.cc b/src/db/db/dbRegionUtils.cc
index 086bbd21c..31f2ccc18 100644
--- a/src/db/db/dbRegionUtils.cc
+++ b/src/db/db/dbRegionUtils.cc
@@ -67,6 +67,7 @@ Edge2EdgeCheckBase::prepare_next_pass ()
   if (! m_ep.empty () && m_has_edge_pair_output) {
 
     std::vector<bool>::const_iterator d = m_ep_discarded.begin ();
+    std::vector<bool>::const_iterator i = m_ep_intra_polygon.begin ();
     std::vector<db::EdgePair>::const_iterator ep = m_ep.begin ();
     while (ep != m_ep.end () && size_t (ep - m_ep.begin ()) < m_first_pseudo) {
       bool use_result = true;
@@ -75,9 +76,10 @@ Edge2EdgeCheckBase::prepare_next_pass ()
         ++d;
       }
       if (use_result) {
-        put (*ep);
+        put (*ep, *i);
       }
       ++ep;
+      ++i;
     }
 
   }
@@ -182,7 +184,10 @@ Edge2EdgeCheckBase::add (const db::Edge *o1, size_t p1, const db::Edge *o2, size
         //  pass we will eliminate those which are shielded completely (with shielding)
         //  and/or compute the negative edges.
         size_t n = m_ep.size ();
+
         m_ep.push_back (ep);
+        m_ep_intra_polygon.push_back (p1 == p2);
+
         m_e2ep.insert (std::make_pair (std::make_pair (*o1, p1), n * 2));
         m_e2ep.insert (std::make_pair (std::make_pair (*o2, p2), n * 2 + 1));
 
@@ -253,9 +258,12 @@ Edge2EdgeCheckBase::add (const db::Edge *o1, size_t p1, const db::Edge *o2, size
     }
 
     //  for negative output edges are cancelled by short interactions perpendicular to them
+    //  For this we have generated "pseudo edges" running along the sides of the original violation. We now check a real
+    //  edge vs. a pseudo edge with the same conditions as the normal interaction and add them to the results. In the
+    //  negative case this means we cancel a real edge.
+
     if (m_has_negative_edge_output &&
-      (m_pseudo_edges.find (std::make_pair (*o1, p1)) != m_pseudo_edges.end () || m_pseudo_edges.find (std::make_pair (*o2, p2)) != m_pseudo_edges.end ()) &&
-      ! (m_pseudo_edges.find (std::make_pair (*o1, p1)) != m_pseudo_edges.end () && m_pseudo_edges.find (std::make_pair (*o2, p2)) != m_pseudo_edges.end ())) {
+      (m_pseudo_edges.find (std::make_pair (*o1, p1)) != m_pseudo_edges.end ()) != (m_pseudo_edges.find (std::make_pair (*o2, p2)) != m_pseudo_edges.end ())) {
 
       //  Overlap or inside checks require input from different layers
       if ((! m_different_polygons || p1 != p2) && (! m_requires_different_layers || ((p1 ^ p2) & 1) != 0)) {
@@ -274,7 +282,10 @@ Edge2EdgeCheckBase::add (const db::Edge *o1, size_t p1, const db::Edge *o2, size
         if (mp_check->check (*o1, *o2, &ep)) {
 
           size_t n = m_ep.size ();
+
           m_ep.push_back (ep);
+          m_ep_intra_polygon.push_back (p1 == p2);  //  not really required, but there for consistency
+
           m_e2ep.insert (std::make_pair (std::make_pair (*o1, p1), n * 2));
           m_e2ep.insert (std::make_pair (std::make_pair (*o2, p2), n * 2 + 1));
 
diff --git a/src/db/db/dbRegionUtils.h b/src/db/db/dbRegionUtils.h
index bcaa65645..a05727604 100644
--- a/src/db/db/dbRegionUtils.h
+++ b/src/db/db/dbRegionUtils.h
@@ -612,7 +612,7 @@ protected:
   /**
    *  @brief Normal edge pair output (violations)
    */
-  virtual void put (const db::EdgePair & /*edge*/) const { }
+  virtual void put (const db::EdgePair & /*edge*/, bool /*intra-polygon*/) const { }
 
   /**
    *  @brief Negative edge output
@@ -628,7 +628,7 @@ private:
   std::multimap<std::pair<db::Edge, size_t>, size_t> m_e2ep;
   std::set<std::pair<db::Edge, size_t> > m_pseudo_edges;
   size_t m_first_pseudo;
-  std::vector<bool> m_ep_discarded;
+  std::vector<bool> m_ep_discarded, m_ep_intra_polygon;
   bool m_with_shielding;
   bool m_has_edge_pair_output;
   bool m_has_negative_edge_output;
@@ -646,19 +646,30 @@ class DB_PUBLIC_TEMPLATE edge2edge_check
 {
 public:
   edge2edge_check (const EdgeRelationFilter &check, Output &output, bool different_polygons, bool requires_different_layers, bool with_shielding)
-    : Edge2EdgeCheckBase (check, different_polygons, requires_different_layers, with_shielding), mp_output (&output)
+    : Edge2EdgeCheckBase (check, different_polygons, requires_different_layers, with_shielding), mp_output_inter (&output), mp_output_intra (0)
+  {
+    //  .. nothing yet ..
+  }
+
+  edge2edge_check (const EdgeRelationFilter &check, Output &output_inter, Output &output_intra, bool different_polygons, bool requires_different_layers, bool with_shielding)
+    : Edge2EdgeCheckBase (check, different_polygons, requires_different_layers, with_shielding), mp_output_inter (&output_inter), mp_output_intra (&output_intra)
   {
     //  .. nothing yet ..
   }
 
 protected:
-  void put (const db::EdgePair &edge) const
+  void put (const db::EdgePair &edge, bool inter_polygon) const
   {
-    mp_output->insert (edge);
+    if (! inter_polygon || ! mp_output_intra) {
+      mp_output_inter->insert (edge);
+    } else {
+      mp_output_intra->insert (edge);
+    }
   }
 
 private:
-  Output *mp_output;
+  Output *mp_output_inter;
+  Output *mp_output_intra;
 };
 
 /**
@@ -669,24 +680,26 @@ private:
  */
 template <class Output, class NegativeEdgeOutput>
 class DB_PUBLIC_TEMPLATE edge2edge_check_with_negative_output
-  : public Edge2EdgeCheckBase
+  : public edge2edge_check<Output>
 {
 public:
   edge2edge_check_with_negative_output (const EdgeRelationFilter &check, Output &output, NegativeEdgeOutput &l1_negative_output, NegativeEdgeOutput &l2_negative_output, bool different_polygons, bool requires_different_layers, bool with_shielding)
-    : Edge2EdgeCheckBase (check, different_polygons, requires_different_layers, with_shielding),
-      mp_output (&output),
+    : edge2edge_check<Output> (check, output, different_polygons, requires_different_layers, with_shielding),
       mp_l1_negative_output (&l1_negative_output),
       mp_l2_negative_output (&l2_negative_output)
   {
-    set_has_negative_edge_output (true);
+    edge2edge_check<Output>::set_has_negative_edge_output (true);
+  }
+
+  edge2edge_check_with_negative_output (const EdgeRelationFilter &check, Output &output_inter, Output &output_intra, NegativeEdgeOutput &l1_negative_output, NegativeEdgeOutput &l2_negative_output, bool different_polygons, bool requires_different_layers, bool with_shielding)
+    : edge2edge_check<Output> (check, output_inter, output_intra, different_polygons, requires_different_layers, with_shielding),
+      mp_l1_negative_output (&l1_negative_output),
+      mp_l2_negative_output (&l2_negative_output)
+  {
+    edge2edge_check<Output>::set_has_negative_edge_output (true);
   }
 
 protected:
-  void put (const db::EdgePair &ep) const
-  {
-    mp_output->insert (ep);
-  }
-
   void put_negative (const db::Edge &edge, int layer) const
   {
     if (layer == 0) {
@@ -698,7 +711,6 @@ protected:
   }
 
 private:
-  Output *mp_output;
   NegativeEdgeOutput *mp_l1_negative_output, *mp_l2_negative_output;
 };
 
@@ -746,35 +758,33 @@ private:
  */
 template <class Output>
 class DB_PUBLIC_TEMPLATE edge2edge_check_negative_or_positive
-  : public Edge2EdgeCheckBase
+  : public edge2edge_check<Output>
 {
 public:
   edge2edge_check_negative_or_positive (const EdgeRelationFilter &check, Output &output, bool negative_output, bool different_polygons, bool requires_different_layers, bool with_shielding)
-    : Edge2EdgeCheckBase (check, different_polygons, requires_different_layers, with_shielding),
-      mp_output (&output)
+    : edge2edge_check<Output> (check, output, different_polygons, requires_different_layers, with_shielding)
   {
-    set_has_negative_edge_output (negative_output);
-    set_has_edge_pair_output (! negative_output);
+    edge2edge_check<Output>::set_has_negative_edge_output (negative_output);
+    edge2edge_check<Output>::set_has_edge_pair_output (! negative_output);
+  }
+
+  edge2edge_check_negative_or_positive (const EdgeRelationFilter &check, Output &output_inter, Output &output_intra, bool negative_output, bool different_polygons, bool requires_different_layers, bool with_shielding)
+    : edge2edge_check<Output> (check, output_inter, output_intra, different_polygons, requires_different_layers, with_shielding)
+  {
+    edge2edge_check<Output>::set_has_negative_edge_output (negative_output);
+    edge2edge_check<Output>::set_has_edge_pair_output (! negative_output);
   }
 
 protected:
   void put_negative (const db::Edge &edge, int layer) const
   {
     if (layer == 0) {
-      mp_output->insert (db::EdgePair (edge, edge.swapped_points ()));
+      edge2edge_check<Output>::put (db::EdgePair (edge, edge.swapped_points ()), false);
     }
     if (layer == 1) {
-      mp_output->insert (db::EdgePair (edge.swapped_points (), edge));
+      edge2edge_check<Output>::put (db::EdgePair (edge.swapped_points (), edge), false);
     }
   }
-
-  void put (const db::EdgePair &edge) const
-  {
-    mp_output->insert (edge);
-  }
-
-private:
-  Output *mp_output;
 };
 
 /**
diff --git a/src/db/db/gsiDeclDbCompoundOperation.cc b/src/db/db/gsiDeclDbCompoundOperation.cc
index b838eae10..0af08a715 100644
--- a/src/db/db/gsiDeclDbCompoundOperation.cc
+++ b/src/db/db/gsiDeclDbCompoundOperation.cc
@@ -426,13 +426,10 @@ static db::CompoundRegionOperationNode *new_width_check (db::Coord d, bool whole
 
 static db::CompoundRegionOperationNode *new_space_or_isolated_check (db::Coord d, bool whole_edges, db::metrics_type metrics, const tl::Variant &ignore_angle, const tl::Variant &min_projection, const tl::Variant &max_projection, bool shielded, db::OppositeFilter opposite_filter, db::RectFilter rect_filter, bool negative, bool isolated)
 {
-  if (opposite_filter != db::NoOppositeFilter || rect_filter != db::NoSideAllowed || shielded) {
-    //  NOTE: we have to use the "foreign" scheme with a filter because only this scheme
-    //  guarantees that all subject shapes are visited and receive all intruders.
-    return new_check_node (new_foreign (), db::SpaceRelation, isolated, d, whole_edges, metrics, ignore_angle, min_projection, max_projection, shielded, opposite_filter, rect_filter, negative);
-  } else {
-    return new_check_node (db::SpaceRelation, isolated, d, whole_edges, metrics, ignore_angle, min_projection, max_projection, shielded, opposite_filter, rect_filter, negative);
-  }
+  //  NOTE: we have to use the "foreign" scheme with a filter because only this scheme
+  //  guarantees that all subject shapes are visited and receive all intruders. Having all intruders is crucial for the
+  //  semantics of the "drc" feature
+  return new_check_node (new_foreign (), db::SpaceRelation, isolated, d, whole_edges, metrics, ignore_angle, min_projection, max_projection, shielded, opposite_filter, rect_filter, negative);
 }
 
 static db::CompoundRegionOperationNode *new_space_check (db::Coord d, bool whole_edges, db::metrics_type metrics, const tl::Variant &ignore_angle, const tl::Variant &min_projection, const tl::Variant &max_projection, bool shielded, db::OppositeFilter opposite_filter, db::RectFilter rect_filter, bool negative)
diff --git a/src/drc/unit_tests/drcGenericTests.cc b/src/drc/unit_tests/drcGenericTests.cc
index f9521822b..a175c6b7b 100644
--- a/src/drc/unit_tests/drcGenericTests.cc
+++ b/src/drc/unit_tests/drcGenericTests.cc
@@ -218,3 +218,23 @@ TEST(15d)
 {
   run_test (_this, "15", true);
 }
+
+TEST(16)
+{
+  run_test (_this, "16", false);
+}
+
+TEST(16d)
+{
+  run_test (_this, "16", true);
+}
+
+TEST(17)
+{
+  run_test (_this, "17", false);
+}
+
+TEST(17d)
+{
+  run_test (_this, "17", true);
+}
diff --git a/src/drc/unit_tests/drcSimpleTests.cc b/src/drc/unit_tests/drcSimpleTests.cc
index 81a76a140..b52c4213f 100644
--- a/src/drc/unit_tests/drcSimpleTests.cc
+++ b/src/drc/unit_tests/drcSimpleTests.cc
@@ -1137,3 +1137,13 @@ TEST(26d_attributes)
 {
   run_test (_this, "26", true);
 }
+
+TEST(27_advancedShielding)
+{
+  run_test (_this, "27", false);
+}
+
+TEST(27d_advancedShielding)
+{
+  run_test (_this, "27", true);
+}
diff --git a/testdata/drc/drcGenericTests_16.drc b/testdata/drc/drcGenericTests_16.drc
new file mode 100644
index 000000000..0f3dc6b40
--- /dev/null
+++ b/testdata/drc/drcGenericTests_16.drc
@@ -0,0 +1,19 @@
+
+source $drc_test_source
+target $drc_test_target
+
+if $drc_test_deep
+  deep
+end
+
+l1 = input(1, 0)
+l2 = input(2, 0)
+l3 = input(3, 0)
+
+l1.output(1, 0)
+l2.output(2, 0)
+l3.output(3, 0)
+
+l1.drc(primary.interacting((space(shielded) < 1.0).polygons)).output(100, 0)
+l1.drc(primary.interacting((space(transparent) < 1.0).polygons)).output(101, 0)
+
diff --git a/testdata/drc/drcGenericTests_16.gds b/testdata/drc/drcGenericTests_16.gds
new file mode 100644
index 000000000..3c1224840
Binary files /dev/null and b/testdata/drc/drcGenericTests_16.gds differ
diff --git a/testdata/drc/drcGenericTests_17.drc b/testdata/drc/drcGenericTests_17.drc
new file mode 100644
index 000000000..d514e859b
--- /dev/null
+++ b/testdata/drc/drcGenericTests_17.drc
@@ -0,0 +1,24 @@
+
+source $drc_test_source
+target $drc_test_target
+
+if $drc_test_deep
+  deep
+end
+
+l1 = input(1, 0)
+l2 = input(2, 0)
+l3 = input(3, 0)
+
+l1.output(1, 0)
+l2.output(2, 0)
+l3.output(3, 0)
+
+# advanced shielding (self, symmetric space)
+
+l1.drc(width(projection, shielded) < 1.0).output(100, 0)
+l1.drc(width(projection, transparent) < 1.0).output(101, 0)
+
+l1.drc(space(projection, shielded) < 1.0).output(110, 0)
+l1.drc(space(projection, transparent) < 1.0).output(111, 0)
+
diff --git a/testdata/drc/drcGenericTests_17.gds b/testdata/drc/drcGenericTests_17.gds
new file mode 100644
index 000000000..ed70cc869
Binary files /dev/null and b/testdata/drc/drcGenericTests_17.gds differ
diff --git a/testdata/drc/drcGenericTests_au16.gds b/testdata/drc/drcGenericTests_au16.gds
new file mode 100644
index 000000000..65c08d8df
Binary files /dev/null and b/testdata/drc/drcGenericTests_au16.gds differ
diff --git a/testdata/drc/drcGenericTests_au16d.gds b/testdata/drc/drcGenericTests_au16d.gds
new file mode 100644
index 000000000..82df8f6df
Binary files /dev/null and b/testdata/drc/drcGenericTests_au16d.gds differ
diff --git a/testdata/drc/drcGenericTests_au17.gds b/testdata/drc/drcGenericTests_au17.gds
new file mode 100644
index 000000000..9e868c17a
Binary files /dev/null and b/testdata/drc/drcGenericTests_au17.gds differ
diff --git a/testdata/drc/drcGenericTests_au17d.gds b/testdata/drc/drcGenericTests_au17d.gds
new file mode 100644
index 000000000..9f9b40744
Binary files /dev/null and b/testdata/drc/drcGenericTests_au17d.gds differ
diff --git a/testdata/drc/drcSimpleTests_27.drc b/testdata/drc/drcSimpleTests_27.drc
new file mode 100644
index 000000000..a068af1b1
--- /dev/null
+++ b/testdata/drc/drcSimpleTests_27.drc
@@ -0,0 +1,24 @@
+
+source $drc_test_source
+target $drc_test_target
+
+if $drc_test_deep
+  deep
+end
+
+l1 = input(1, 0)
+l2 = input(2, 0)
+l3 = input(3, 0)
+
+l1.output(1, 0)
+l2.output(2, 0)
+l3.output(3, 0)
+
+# advanced shielding (self, symmetric space)
+
+l1.width(1.0, projection, shielded).output(100, 0)
+l1.width(1.0, projection, transparent).output(101, 0)
+
+l1.space(1.0, projection, shielded).output(110, 0)
+l1.space(1.0, projection, transparent).output(111, 0)
+
diff --git a/testdata/drc/drcSimpleTests_27.gds b/testdata/drc/drcSimpleTests_27.gds
new file mode 100644
index 000000000..ed70cc869
Binary files /dev/null and b/testdata/drc/drcSimpleTests_27.gds differ
diff --git a/testdata/drc/drcSimpleTests_au27.gds b/testdata/drc/drcSimpleTests_au27.gds
new file mode 100644
index 000000000..e36adc82a
Binary files /dev/null and b/testdata/drc/drcSimpleTests_au27.gds differ
diff --git a/testdata/drc/drcSimpleTests_au27d.gds b/testdata/drc/drcSimpleTests_au27d.gds
new file mode 100644
index 000000000..c1d38d1eb
Binary files /dev/null and b/testdata/drc/drcSimpleTests_au27d.gds differ
diff --git a/testdata/drc/drcSuiteTests.drc b/testdata/drc/drcSuiteTests.drc
index 26e7d5e01..9574e8e96 100644
--- a/testdata/drc/drcSuiteTests.drc
+++ b/testdata/drc/drcSuiteTests.drc
@@ -321,19 +321,16 @@ def run_testsuite(dm, ic, tiled = false, hier = false)
   lb += 10 #230
   message "--- isolated #{lb}"
   
-  b.isolated(0.4).polygons.output(lb, dm)
-  b.isolated(0.4).polygons.xor(b.iso(0.4).polygons).is_empty? == true || raise("xor not empty")
-  b.isolated(0.4, euclidian).polygons.output(lb + 1, dm)
-  b.isolated(0.4, square).polygons.output(lb + 2, dm)
-  b.isolated(0.4, projection).polygons.output(lb + 3, dm)
-  b.isolated(0.4, euclidian, whole_edges).polygons.output(lb + 4, dm)
-  b.isolated(0.4, euclidian, projection_limits(0.4, nil)).polygons.output(lb + 5, dm)
-  b.isolated(0.4, euclidian, projection_limits(nil, 0.4)).polygons.output(lb + 6, dm)
-  if has_float_range
-    b.isolated(0.4, euclidian, projection_limits(0..0.4)).polygons.output(lb + 7, dm)
-  else
-    b.isolated(0.4, euclidian, projection_limits(0, 0.4)).polygons.output(lb + 7, dm)
-  end
+  b.isolated(0.4, shielded).polygons.output(lb, dm)
+  b.isolated(0.4, shielded).polygons.xor(b.iso(0.4, shielded).polygons).is_empty? == true || raise("xor not empty")
+  b.isolated(0.4, shielded, euclidian).polygons.output(lb + 1, dm)
+  b.isolated(0.4, shielded, square).polygons.output(lb + 2, dm)
+  b.isolated(0.4, shielded, projection).polygons.output(lb + 3, dm)
+  b.isolated(0.4, shielded, euclidian, whole_edges).polygons.output(lb + 4, dm)
+  b.isolated(0.4, shielded, euclidian, projection_limits(0.4, nil)).polygons.output(lb + 5, dm)
+  b.isolated(0.4, shielded, euclidian, projection_limits(nil, 0.4)).polygons.output(lb + 6, dm)
+  b.isolated(0.4, shielded, euclidian, projecting < 0.4).polygons.output(lb + 7, dm)
+  b.isolated(0.4, transparent).polygons.output(lb + 8, dm)
   
   lb += 10 #240
   message "--- notch #{lb}"
diff --git a/testdata/drc/drcSuiteTests_au2.oas b/testdata/drc/drcSuiteTests_au2.oas
index 6c57f6f21..8a5528975 100644
Binary files a/testdata/drc/drcSuiteTests_au2.oas and b/testdata/drc/drcSuiteTests_au2.oas differ