diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index cb20397..3ac6259 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -143,6 +143,7 @@ set(solvespace_cad_SOURCES
     mesh.cpp
     modify.cpp
     mouse.cpp
+    polyline.cpp
     polygon.cpp
     resource.cpp
     request.cpp
diff --git a/src/dsc.h b/src/dsc.h
index 3a895b4..7769621 100644
--- a/src/dsc.h
+++ b/src/dsc.h
@@ -107,6 +107,14 @@ public:
     Vector4 Project4d() const;
 };
 
+struct VectorHash {
+    size_t operator()(const Vector &v) const;
+};
+
+struct VectorPred {
+    bool operator()(Vector a, Vector b) const;
+};
+
 class Vector4 {
 public:
     double w, x, y, z;
diff --git a/src/exportvector.cpp b/src/exportvector.cpp
index 4dcf685..8732433 100644
--- a/src/exportvector.cpp
+++ b/src/exportvector.cpp
@@ -6,134 +6,6 @@
 #include <libdxfrw.h>
 #include "solvespace.h"
 
-class PolylineBuilder {
-public:
-    struct Edge;
-
-    struct Vertex {
-        Vector              pos;
-        std::vector<Edge *> edges;
-
-        bool getNext(hStyle hs, Vertex **next) {
-            auto it = std::find_if(edges.begin(), edges.end(), [&](const Edge *e) {
-                return e->tag == 0 && e->style.v == hs.v;
-            });
-            if(it != edges.end()) {
-                (*it)->tag = 1;
-                *next = (*it)->getOtherVertex(this);
-                return true;
-            } else {
-                return false;
-            }
-        }
-
-        size_t countEdgesWithTagAndStyle(int tag, hStyle hs) const {
-            return std::count_if(edges.begin(), edges.end(), [&](const Edge *e) {
-                return e->tag == tag && e->style.v == hs.v;
-            });
-        }
-    };
-
-    struct Edge {
-        Vertex *a;
-        Vertex *b;
-        hStyle  style;
-        int     tag;
-
-        Vertex *getOtherVertex(Vertex *v) {
-            if(a == v) return b;
-            if(b == v) return a;
-            return NULL;
-        }
-
-        bool getStartAndNext(Vertex **start, Vertex **next, bool loop) {
-            size_t numA = a->countEdgesWithTagAndStyle(0, style);
-            size_t numB = b->countEdgesWithTagAndStyle(0, style);
-
-            if((numA == 1 && numB > 1) || (loop && numA > 1 && numB > 1)) {
-                *start = a;
-                *next = b;
-                return true;
-            }
-
-            if(numA > 1 && numB == 1) {
-                *start = b;
-                *next = a;
-                return true;
-            }
-
-            return false;
-        }
-    };
-
-    struct VectorHash {
-        size_t operator()(const Vector &v) const {
-            static const size_t size = std::numeric_limits<size_t>::max() / 2 - 1;
-            static const double eps = (4.0 * LENGTH_EPS);
-
-            double x = fabs(v.x) / eps;
-            double y = fabs(v.y) / eps;
-
-            size_t xs = size_t(fmod(x, double(size)));
-            size_t ys = size_t(fmod(y, double(size)));
-
-            return ys * size + xs;
-        }
-    };
-
-    struct VectorPred {
-        bool operator()(Vector a, Vector b) const {
-            return a.Equals(b, LENGTH_EPS);
-        }
-    };
-
-    std::unordered_map<Vector, Vertex *, VectorHash, VectorPred> vertices;
-    std::vector<Edge *> edges;
-
-    ~PolylineBuilder() {
-        clear();
-    }
-
-    void clear() {
-        for(Edge *e : edges) {
-            delete e;
-        }
-        edges.clear();
-
-        for(auto &v : vertices) {
-            delete v.second;
-        }
-        vertices.clear();
-    }
-
-    Vertex *addVertex(const Vector &pos) {
-        auto it = vertices.find(pos);
-        if(it != vertices.end()) {
-            return it->second;
-        }
-
-        Vertex *result = new Vertex;
-        result->pos = pos;
-        vertices.emplace(pos, result);
-
-        return result;
-    }
-
-    Edge *addEdge(const Vector &p0, const Vector &p1, int style) {
-        Vertex *v0 = addVertex(p0);
-        Vertex *v1 = addVertex(p1);
-        if(v0 == v1) return NULL;
-
-        Edge *edge = new Edge { v0, v1, hStyle { (uint32_t)style }, 0 };
-        edges.push_back(edge);
-
-        v0->edges.push_back(edge);
-        v1->edges.push_back(edge);
-
-        return edge;
-    }
-};
-
 //-----------------------------------------------------------------------------
 // Routines for DXF export
 //-----------------------------------------------------------------------------
@@ -245,43 +117,36 @@ public:
         for(DxfFileWriter::BezierPath &path : writer->paths) {
             for(SBezier *sb : path.beziers) {
                 if(sb->deg != 1) continue;
-                builder.addEdge(sb->ctrl[0], sb->ctrl[1], sb->auxA);
+                builder.AddEdge(sb->ctrl[0], sb->ctrl[1], (uint32_t)sb->auxA);
             }
         }
 
-        bool found;
-        bool loop = false;
-        do {
-            found = false;
-            for(PolylineBuilder::Edge *e : builder.edges) {
-                if(e->tag != 0) continue;
+        DRW_LWPolyline polyline;
 
-                PolylineBuilder::Vertex *start;
-                PolylineBuilder::Vertex *next;
-                if(!e->getStartAndNext(&start, &next, loop)) continue;
-                found = true;
-                e->tag = 1;
+        auto startFunc = [&](PolylineBuilder::Vertex *start,
+                             PolylineBuilder::Vertex *next,
+                             PolylineBuilder::Edge *e) {
+            hStyle hs = { e->kind };
+            polyline = {};
+            assignEntityDefaults(&polyline, hs);
+            polyline.vertlist.push_back(new DRW_Vertex2D(start->pos.x, start->pos.y, 0.0));
+            polyline.vertlist.push_back(new DRW_Vertex2D(next->pos.x, next->pos.y, 0.0));
+        };
 
-                DRW_LWPolyline polyline;
-                assignEntityDefaults(&polyline, e->style);
-                polyline.vertlist.push_back(new DRW_Vertex2D(start->pos.x, start->pos.y, 0.0));
-                polyline.vertlist.push_back(new DRW_Vertex2D(next->pos.x, next->pos.y, 0.0));
-                while(next->getNext(e->style, &next)) {
-                    polyline.vertlist.push_back(new DRW_Vertex2D(next->pos.x, next->pos.y, 0.0));
-                }
-                dxf->writeLWPolyline(&polyline);
-            }
+        auto nextFunc = [&](PolylineBuilder::Vertex *next, PolylineBuilder::Edge *e) {
+            polyline.vertlist.push_back(new DRW_Vertex2D(next->pos.x, next->pos.y, 0.0));
+        };
 
-            if(!found && !loop) {
-                loop  = true;
-                found = true;
-            }
-        } while(found);
+        auto endFunc = [&]() {
+            dxf->writeLWPolyline(&polyline);
+        };
 
-        for(PolylineBuilder::Edge *e : builder.edges) {
-            if(e->tag != 0) continue;
-            writeLine(e->a->pos, e->b->pos, e->style);
-        }
+        auto aloneFunc = [&](PolylineBuilder::Edge *e) {
+            hStyle hs = { e->kind };
+            writeLine(e->a->pos, e->b->pos, hs);
+        };
+
+        builder.Generate(startFunc, nextFunc, aloneFunc, endFunc);
     }
 
     void writeEntities() override {
diff --git a/src/polygon.h b/src/polygon.h
index bc3e085..2ef818c 100644
--- a/src/polygon.h
+++ b/src/polygon.h
@@ -349,5 +349,54 @@ public:
     void SnapToVertex(Vector v, SMesh *extras);
 };
 
+class PolylineBuilder {
+public:
+    struct Edge;
+
+    struct Vertex {
+        Vector              pos;
+        std::vector<Edge *> edges;
+
+        bool GetNext(uint32_t kind, Vertex **next, Edge **nextEdge);
+        bool GetNext(uint32_t kind, Vector plane, double d, Vertex **next, Edge **nextEdge);
+        size_t CountEdgesWithTagAndKind(int tag, uint32_t kind) const;
+    };
+
+    struct VertexPairHash {
+        size_t operator()(const std::pair<Vertex *, Vertex *> &v) const;
+    };
+
+    struct Edge {
+        Vertex   *a;
+        Vertex   *b;
+        uint32_t  kind;
+        int       tag;
+
+        union {
+            uintptr_t  data;
+            SOutline  *outline;
+            SEdge     *edge;
+        };
+
+        Vertex *GetOtherVertex(Vertex *v) const;
+        bool GetStartAndNext(Vertex **start, Vertex **next, bool loop) const;
+    };
+
+    std::unordered_map<Vector, Vertex *, VectorHash, VectorPred> vertices;
+    std::unordered_map<std::pair<Vertex *, Vertex *>, Edge *, VertexPairHash> edgeMap;
+    std::vector<Edge *> edges;
+
+    ~PolylineBuilder();
+    void Clear();
+
+    Vertex *AddVertex(const Vector &pos);
+    Edge *AddEdge(const Vector &p0, const Vector &p1, uint32_t kind, uintptr_t data = 0);
+    void Generate(
+        std::function<void(Vertex *start, Vertex *next, Edge *edge)> startFunc,
+        std::function<void(Vertex *next, Edge *edge)> nextFunc,
+        std::function<void(Edge *)> aloneFunc,
+        std::function<void()> endFunc = [](){});
+};
+
 #endif
 
diff --git a/src/polyline.cpp b/src/polyline.cpp
new file mode 100644
index 0000000..f7dcace
--- /dev/null
+++ b/src/polyline.cpp
@@ -0,0 +1,189 @@
+//-----------------------------------------------------------------------------
+// A helper class to assemble scattered edges into contiguous polylines,
+// as nicely as possible.
+//
+// Copyright 2016 M-Labs Ltd
+//-----------------------------------------------------------------------------
+#include "solvespace.h"
+
+bool PolylineBuilder::Vertex::GetNext(uint32_t kind, Vertex **next, Edge **nextEdge) {
+    auto it = std::find_if(edges.begin(), edges.end(), [&](const Edge *e) {
+        return e->tag == 0 && e->kind == kind;
+    });
+
+    if(it != edges.end()) {
+        (*it)->tag = 1;
+        *next = (*it)->GetOtherVertex(this);
+        *nextEdge = *it;
+        return true;
+    }
+
+    return false;
+}
+
+bool PolylineBuilder::Vertex::GetNext(uint32_t kind, Vector plane, double dist,
+                                      Vertex **next, Edge **nextEdge) {
+    Edge *best = NULL;
+    double minD = VERY_POSITIVE;
+    for(Edge *e : edges) {
+        if(e->tag != 0) continue;
+        if(e->kind != kind) continue;
+
+        // We choose the best next edge with minimal distance from the current plane
+        Vector nextPos = e->GetOtherVertex(this)->pos;
+        double curD = fabs(plane.Dot(nextPos) - dist);
+        if(best != NULL && curD > minD) continue;
+        best = e;
+        minD = curD;
+    }
+
+    if(best != NULL) {
+        best->tag = 1;
+        *next = best->GetOtherVertex(this);
+        *nextEdge = best;
+        return true;
+    }
+
+    return false;
+}
+
+
+size_t PolylineBuilder::Vertex::CountEdgesWithTagAndKind(int tag, uint32_t kind) const {
+    return std::count_if(edges.begin(), edges.end(), [&](const Edge *e) {
+        return e->tag == tag && e->kind == kind;
+    });
+}
+
+PolylineBuilder::Vertex *PolylineBuilder::Edge::GetOtherVertex(PolylineBuilder::Vertex *v) const {
+    if(a == v) return b;
+    if(b == v) return a;
+    return NULL;
+}
+
+size_t PolylineBuilder::VertexPairHash::operator()(const std::pair<Vertex *, Vertex *> &v) const {
+    return ((uintptr_t)v.first / sizeof(Vertex)) ^
+           ((uintptr_t)v.second / sizeof(Vertex));
+}
+
+bool PolylineBuilder::Edge::GetStartAndNext(PolylineBuilder::Vertex **start,
+                                            PolylineBuilder::Vertex **next, bool loop) const {
+    size_t numA = a->CountEdgesWithTagAndKind(0, kind);
+    size_t numB = b->CountEdgesWithTagAndKind(0, kind);
+
+    if((numA == 1 && numB > 1) || (loop && numA > 1 && numB > 1)) {
+        *start = a;
+        *next = b;
+        return true;
+    }
+
+    if(numA > 1 && numB == 1) {
+        *start = b;
+        *next = a;
+        return true;
+    }
+
+    return false;
+}
+
+PolylineBuilder::~PolylineBuilder() {
+    Clear();
+}
+
+void PolylineBuilder::Clear() {
+    for(Edge *e : edges) {
+        delete e;
+    }
+    edges.clear();
+
+    for(auto &v : vertices) {
+        delete v.second;
+    }
+    vertices.clear();
+}
+
+PolylineBuilder::Vertex *PolylineBuilder::AddVertex(const Vector &pos) {
+    auto it = vertices.find(pos);
+    if(it != vertices.end()) {
+        return it->second;
+    }
+
+    Vertex *result = new Vertex;
+    result->pos = pos;
+    vertices.emplace(pos, result);
+
+    return result;
+}
+
+PolylineBuilder::Edge *PolylineBuilder::AddEdge(const Vector &p0, const Vector &p1,
+                                                uint32_t kind, uintptr_t data) {
+    Vertex *v0 = AddVertex(p0);
+    Vertex *v1 = AddVertex(p1);
+    if(v0 == v1) return NULL;
+
+    auto it = edgeMap.find(std::make_pair(v0, v1));
+    if(it != edgeMap.end()) {
+        return it->second;
+    }
+
+    PolylineBuilder::Edge *edge = new PolylineBuilder::Edge {};
+    edge->a = v0;
+    edge->b = v1;
+    edge->kind = kind;
+    edge->tag = 0;
+    edge->data = data;
+    edges.push_back(edge);
+    edgeMap.emplace(std::make_pair(v0, v1), edge);
+
+    v0->edges.push_back(edge);
+    v1->edges.push_back(edge);
+
+    return edge;
+}
+
+void PolylineBuilder::Generate(
+        std::function<void(Vertex *start, Vertex *next, Edge *edge)> startFunc,
+        std::function<void(Vertex *next, Edge *edge)> nextFunc,
+        std::function<void(Edge *alone)> aloneFunc,
+        std::function<void()> endFunc) {
+    bool found;
+    bool loop = false;
+    do {
+        found = false;
+        for(PolylineBuilder::Edge *e : edges) {
+            if(e->tag != 0) continue;
+
+            Vertex *start;
+            Vertex *next;
+            if(!e->GetStartAndNext(&start, &next, loop)) continue;
+
+            Vector startPos = start->pos;
+            Vector nextPos = next->pos;
+            found = true;
+            e->tag = 1;
+
+            startFunc(start, next, e);
+
+            Edge *nextEdge;
+            if(next->GetNext(e->kind, &next, &nextEdge)) {
+                Vector plane = nextPos.Minus(startPos).Cross(next->pos.Minus(startPos));
+                double dist = plane.Dot(startPos);
+                nextFunc(next, nextEdge);
+                while(next->GetNext(e->kind, plane, dist, &next, &nextEdge)) {
+                    nextFunc(next, nextEdge);
+                }
+            }
+
+            endFunc();
+        }
+
+        if(!found && !loop) {
+            loop  = true;
+            found = true;
+        }
+    } while(found);
+
+    for(PolylineBuilder::Edge *e : edges) {
+        if(e->tag != 0) continue;
+        aloneFunc(e);
+    }
+}
diff --git a/src/util.cpp b/src/util.cpp
index 3a32ab9..f22fc1b 100644
--- a/src/util.cpp
+++ b/src/util.cpp
@@ -935,6 +935,25 @@ Vector Vector::AtIntersectionOfPlanes(Vector na, double da,
     return Vector::From(detx/det, dety/det, detz/det);
 }
 
+size_t VectorHash::operator()(const Vector &v) const {
+    const size_t size = (size_t)pow(std::numeric_limits<size_t>::max(), 1.0 / 3.0) - 1;
+    const double eps = 4.0 * LENGTH_EPS;
+
+    double x = fabs(v.x) / eps;
+    double y = fabs(v.y) / eps;
+    double z = fabs(v.y) / eps;
+
+    size_t xs = size_t(fmod(x, (double)size));
+    size_t ys = size_t(fmod(y, (double)size));
+    size_t zs = size_t(fmod(z, (double)size));
+
+    return (zs * size + ys) * size + xs;
+}
+
+bool VectorPred::operator()(Vector a, Vector b) const {
+    return a.Equals(b, LENGTH_EPS);
+}
+
 Vector4 Vector4::From(double w, double x, double y, double z) {
     Vector4 ret;
     ret.w = w;