diff --git a/src/groupmesh.cpp b/src/groupmesh.cpp
index afd76bb..dac5869 100644
--- a/src/groupmesh.cpp
+++ b/src/groupmesh.cpp
@@ -401,12 +401,18 @@ void Group::GenerateDisplayItems() {
             displayOutlines.Clear();
 
             if(SS.GW.showEdges || SS.GW.showOutlines) {
+                SOutlineList rawOutlines = {};
                 if(runningMesh.l.n > 0) {
                     // Triangle mesh only; no shell or emphasized edges.
-                    runningMesh.MakeOutlinesInto(&displayOutlines, EdgeKind::EMPHASIZED);
+                    runningMesh.MakeOutlinesInto(&rawOutlines, EdgeKind::EMPHASIZED);
                 } else {
-                    displayMesh.MakeOutlinesInto(&displayOutlines, EdgeKind::SHARP);
+                    displayMesh.MakeOutlinesInto(&rawOutlines, EdgeKind::SHARP);
                 }
+
+                PolylineBuilder builder;
+                builder.MakeFromOutlines(rawOutlines);
+                builder.GenerateOutlines(&displayOutlines);
+                rawOutlines.Clear();
             }
         }
 
diff --git a/src/polygon.h b/src/polygon.h
index 2ef818c..8136860 100644
--- a/src/polygon.h
+++ b/src/polygon.h
@@ -396,6 +396,11 @@ public:
         std::function<void(Vertex *next, Edge *edge)> nextFunc,
         std::function<void(Edge *)> aloneFunc,
         std::function<void()> endFunc = [](){});
+
+    void MakeFromEdges(const SEdgeList &sel);
+    void MakeFromOutlines(const SOutlineList &sol);
+    void GenerateEdges(SEdgeList *sel);
+    void GenerateOutlines(SOutlineList *sol);
 };
 
 #endif
diff --git a/src/polyline.cpp b/src/polyline.cpp
index f7dcace..bddf1ab 100644
--- a/src/polyline.cpp
+++ b/src/polyline.cpp
@@ -187,3 +187,58 @@ void PolylineBuilder::Generate(
         aloneFunc(e);
     }
 }
+
+void PolylineBuilder::MakeFromEdges(const SEdgeList &sel) {
+    for(const SEdge &se : sel.l) {
+        AddEdge(se.a, se.b, (uint32_t)se.auxA, reinterpret_cast<uintptr_t>(&se));
+    }
+}
+
+void PolylineBuilder::MakeFromOutlines(const SOutlineList &ol) {
+    for(const SOutline &so : ol.l) {
+        // Use outline tag as kind, so that emphasized and contour outlines
+        // would not be composed together.
+        AddEdge(so.a, so.b, (uint32_t)so.tag, reinterpret_cast<uintptr_t>(&so));
+    }
+}
+
+void PolylineBuilder::GenerateEdges(SEdgeList *sel) {
+    Vector prev;
+    auto startFunc = [&](Vertex *start, Vertex *next, Edge *e) {
+        sel->AddEdge(start->pos, next->pos, e->kind);
+        prev = next->pos;
+    };
+
+    auto nextFunc = [&](Vertex *next, Edge *e) {
+        sel->AddEdge(prev, next->pos, e->kind);
+        prev = next->pos;
+    };
+
+    auto aloneFunc = [&](Edge *e) {
+        sel->AddEdge(e->a->pos, e->b->pos, e->kind);
+    };
+
+    Generate(startFunc, nextFunc, aloneFunc);
+}
+
+void PolylineBuilder::GenerateOutlines(SOutlineList *sol) {
+    Vector prev;
+    auto startFunc = [&](Vertex *start, Vertex *next, Edge *e) {
+        SOutline *so = e->outline;
+        sol->AddEdge(start->pos, next->pos, so->nl, so->nr, so->tag);
+        prev = next->pos;
+    };
+
+    auto nextFunc = [&](Vertex *next, Edge *e) {
+        SOutline *so = e->outline;
+        sol->AddEdge(prev, next->pos, so->nl, so->nr, so->tag);
+        prev = next->pos;
+    };
+
+    auto aloneFunc = [&](Edge *e) {
+        SOutline *so = e->outline;
+        sol->AddEdge(so->a, so->b, so->nl, so->nr, so->tag);
+    };
+
+    Generate(startFunc, nextFunc, aloneFunc);
+}