diff --git a/src/libslic3r/Line.hpp b/src/libslic3r/Line.hpp
index b593d2f7b7..f53479a9f2 100644
--- a/src/libslic3r/Line.hpp
+++ b/src/libslic3r/Line.hpp
@@ -194,7 +194,7 @@ template<class L> bool intersection(const L &l1, const L &l2, Vec<Dim<L>, Scalar
 class Line
 {
 public:
-    Line() {}
+    Line() = default;
     Line(const Point& _a, const Point& _b) : a(_a), b(_b) {}
     explicit operator Lines() const { Lines lines; lines.emplace_back(*this); return lines; }
     void   scale(double factor) { this->a *= factor; this->b *= factor; }
diff --git a/src/libslic3r/Polyline.cpp b/src/libslic3r/Polyline.cpp
index 3635b93faa..92878c34ac 100644
--- a/src/libslic3r/Polyline.cpp
+++ b/src/libslic3r/Polyline.cpp
@@ -297,6 +297,44 @@ std::pair<int, Point> foot_pt(const Points &polyline, const Point &pt)
     return std::make_pair(int(it_proj - polyline.begin()) - 1, foot_pt_min);
 }
 
+size_t total_lines_count(const ThickPolylines &thick_polylines) {
+    size_t lines_cnt = 0;
+    for (const ThickPolyline &thick_polyline : thick_polylines) {
+        if (thick_polyline.points.size() > 1) {
+            lines_cnt += thick_polyline.points.size() - 1;
+        }
+    }
+
+    return lines_cnt;
+}
+
+Lines to_lines(const ThickPolyline &thick_polyline) {
+    Lines lines;
+    if (thick_polyline.points.size() >= 2) {
+        lines.reserve(thick_polyline.points.size() - 1);
+
+        for (Points::const_iterator it = thick_polyline.points.begin(); it != thick_polyline.points.end() - 1; ++it) {
+            lines.emplace_back(*it, *(it + 1));
+        }
+    }
+
+    return lines;
+}
+
+Lines to_lines(const ThickPolylines &thick_polylines) {
+    const size_t lines_cnt = total_lines_count(thick_polylines);
+
+    Lines lines;
+    lines.reserve(lines_cnt);
+    for (const ThickPolyline &thick_polyline : thick_polylines) {
+        for (Points::const_iterator it = thick_polyline.points.begin(); it != thick_polyline.points.end() - 1; ++it) {
+            lines.emplace_back(*it, *(it + 1));
+        }
+    }
+
+    return lines;
+}
+
 ThickLines ThickPolyline::thicklines() const
 {
     ThickLines lines;
diff --git a/src/libslic3r/Polyline.hpp b/src/libslic3r/Polyline.hpp
index 0357ebb534..0f928328a7 100644
--- a/src/libslic3r/Polyline.hpp
+++ b/src/libslic3r/Polyline.hpp
@@ -119,30 +119,40 @@ inline double total_length(const Polylines &polylines) {
     return total;
 }
 
-inline Lines to_lines(const Polyline &poly) 
-{
+inline size_t total_lines_count(const Polylines &polylines) {
+    size_t lines_cnt = 0;
+    for (const Polyline &polyline : polylines) {
+        if (polyline.points.size() > 1) {
+            lines_cnt += polyline.points.size() - 1;
+        }
+    }
+
+    return lines_cnt;
+}
+
+inline Lines to_lines(const Polyline &poly) {
     Lines lines;
     if (poly.points.size() >= 2) {
         lines.reserve(poly.points.size() - 1);
-        for (Points::const_iterator it = poly.points.begin(); it != poly.points.end()-1; ++it)
-            lines.push_back(Line(*it, *(it + 1)));
+        for (Points::const_iterator it = poly.points.begin(); it != poly.points.end() - 1; ++it) {
+            lines.emplace_back(*it, *(it + 1));
+        }
     }
+
     return lines;
 }
 
-inline Lines to_lines(const Polylines &polys) 
-{
-    size_t n_lines = 0;
-    for (size_t i = 0; i < polys.size(); ++ i)
-        if (polys[i].points.size() > 1)
-            n_lines += polys[i].points.size() - 1;
+inline Lines to_lines(const Polylines &polylines) {
+    const size_t lines_cnt = total_lines_count(polylines);
+
     Lines lines;
-    lines.reserve(n_lines);
-    for (size_t i = 0; i < polys.size(); ++ i) {
-        const Polyline &poly = polys[i];
-        for (Points::const_iterator it = poly.points.begin(); it != poly.points.end()-1; ++it)
-            lines.push_back(Line(*it, *(it + 1)));
+    lines.reserve(lines_cnt);
+    for (const Polyline &polyline : polylines) {
+        for (Points::const_iterator it = polyline.points.begin(); it != polyline.points.end() - 1; ++it) {
+            lines.emplace_back(*it, *(it + 1));
+        }
     }
+
     return lines;
 }
 
@@ -251,6 +261,11 @@ inline ThickPolylines to_thick_polylines(Polylines &&polylines, const coordf_t w
     return out;
 }
 
+size_t total_lines_count(const ThickPolylines &thick_polylines);
+
+Lines to_lines(const ThickPolyline &thick_polyline);
+Lines to_lines(const ThickPolylines &thick_polylines);
+
 class Polyline3 : public MultiPoint3
 {
 public: