diff --git a/src/libslic3r/CMakeLists.txt b/src/libslic3r/CMakeLists.txt
index 1a9a153b94..85e11eded3 100644
--- a/src/libslic3r/CMakeLists.txt
+++ b/src/libslic3r/CMakeLists.txt
@@ -127,6 +127,8 @@ add_library(libslic3r STATIC
     Point.hpp
     Polygon.cpp
     Polygon.hpp
+    PolygonTrimmer.cpp
+    PolygonTrimmer.hpp
     Polyline.cpp
     Polyline.hpp
     PolylineCollection.cpp
diff --git a/src/libslic3r/EdgeGrid.cpp b/src/libslic3r/EdgeGrid.cpp
index 9d02ef09b7..f40d499de1 100644
--- a/src/libslic3r/EdgeGrid.cpp
+++ b/src/libslic3r/EdgeGrid.cpp
@@ -11,6 +11,7 @@
 #include "libslic3r.h"
 #include "ClipperUtils.hpp"
 #include "EdgeGrid.hpp"
+#include "Geometry.hpp"
 #include "SVG.hpp"
 
 #if 0
@@ -275,134 +276,24 @@ void EdgeGrid::Grid::create_from_m_contours(coord_t resolution)
 	// 6) Finally fill in m_cell_data by rasterizing the lines once again.
 	for (size_t i = 0; i < m_cells.size(); ++i)
 		m_cells[i].end = m_cells[i].begin;
-	for (size_t i = 0; i < m_contours.size(); ++i) {
-		const Slic3r::Points &pts = *m_contours[i];
-		for (size_t j = 0; j < pts.size(); ++j) {
-			// End points of the line segment.
-			Slic3r::Point p1(pts[j]);
-			Slic3r::Point p2 = pts[(j + 1 == pts.size()) ? 0 : j + 1];
-			p1(0) -= m_bbox.min(0);
-			p1(1) -= m_bbox.min(1);
-			p2(0) -= m_bbox.min(0);
-			p2(1) -= m_bbox.min(1);
-			// Get the cells of the end points.
-			coord_t ix = p1(0) / m_resolution;
-			coord_t iy = p1(1) / m_resolution;
-			coord_t ixb = p2(0) / m_resolution;
-			coord_t iyb = p2(1) / m_resolution;
-			assert(ix >= 0 && size_t(ix) < m_cols);
-			assert(iy >= 0 && size_t(iy) < m_rows);
-			assert(ixb >= 0 && size_t(ixb) < m_cols);
-			assert(iyb >= 0 && size_t(iyb) < m_rows);
-			// Account for the end points.
-			m_cell_data[m_cells[iy*m_cols + ix].end++] = std::pair<size_t, size_t>(i, j);
-			if (ix == ixb && iy == iyb)
-				// Both ends fall into the same cell.
-				continue;
-			// Raster the centeral part of the line.
-			coord_t dx = std::abs(p2(0) - p1(0));
-			coord_t dy = std::abs(p2(1) - p1(1));
-			if (p1(0) < p2(0)) {
-				int64_t ex = int64_t((ix + 1)*m_resolution - p1(0)) * int64_t(dy);
-				if (p1(1) < p2(1)) {
-					// x positive, y positive
-					int64_t ey = int64_t((iy + 1)*m_resolution - p1(1)) * int64_t(dx);
-					do {
-						assert(ix <= ixb && iy <= iyb);
-						if (ex < ey) {
-							ey -= ex;
-							ex = int64_t(dy) * m_resolution;
-							ix += 1;
-						}
-						else if (ex == ey) {
-							ex = int64_t(dy) * m_resolution;
-							ey = int64_t(dx) * m_resolution;
-							ix += 1;
-							iy += 1;
-						}
-						else {
-							assert(ex > ey);
-							ex -= ey;
-							ey = int64_t(dx) * m_resolution;
-							iy += 1;
-						}
-						m_cell_data[m_cells[iy*m_cols + ix].end++] = std::pair<size_t, size_t>(i, j);
-					} while (ix != ixb || iy != iyb);
-				}
-				else {
-					// x positive, y non positive
-					int64_t ey = int64_t(p1(1) - iy*m_resolution) * int64_t(dx);
-					do {
-						assert(ix <= ixb && iy >= iyb);
-						if (ex <= ey) {
-							ey -= ex;
-							ex = int64_t(dy) * m_resolution;
-							ix += 1;
-						}
-						else {
-							ex -= ey;
-							ey = int64_t(dx) * m_resolution;
-							iy -= 1;
-						}
-						m_cell_data[m_cells[iy*m_cols + ix].end++] = std::pair<size_t, size_t>(i, j);
-					} while (ix != ixb || iy != iyb);
-				}
-			}
-			else {
-				int64_t ex = int64_t(p1(0) - ix*m_resolution) * int64_t(dy);
-				if (p1(1) < p2(1)) {
-					// x non positive, y positive
-					int64_t ey = int64_t((iy + 1)*m_resolution - p1(1)) * int64_t(dx);
-					do {
-						assert(ix >= ixb && iy <= iyb);
-						if (ex < ey) {
-							ey -= ex;
-							ex = int64_t(dy) * m_resolution;
-							ix -= 1;
-						}
-						else {
-							assert(ex >= ey);
-							ex -= ey;
-							ey = int64_t(dx) * m_resolution;
-							iy += 1;
-						}
-						m_cell_data[m_cells[iy*m_cols + ix].end++] = std::pair<size_t, size_t>(i, j);
-					} while (ix != ixb || iy != iyb);
-				}
-				else {
-					// x non positive, y non positive
-					int64_t ey = int64_t(p1(1) - iy*m_resolution) * int64_t(dx);
-					do {
-						assert(ix >= ixb && iy >= iyb);
-						if (ex < ey) {
-							ey -= ex;
-							ex = int64_t(dy) * m_resolution;
-							ix -= 1;
-						}
-						else if (ex == ey) {
-							// The lower edge of a grid cell belongs to the cell.
-							// Handle the case where the ray may cross the lower left corner of a cell in a general case,
-							// or a left or lower edge in a degenerate case (horizontal or vertical line).
-							if (dx > 0) {
-								ex = int64_t(dy) * m_resolution;
-								ix -= 1;
-							}
-							if (dy > 0) {
-								ey = int64_t(dx) * m_resolution;
-								iy -= 1;
-							}
-						}
-						else {
-							assert(ex > ey);
-							ex -= ey;
-							ey = int64_t(dx) * m_resolution;
-							iy -= 1;
-						}
-						m_cell_data[m_cells[iy*m_cols + ix].end++] = std::pair<size_t, size_t>(i, j);
-					} while (ix != ixb || iy != iyb);
-				}
-			}
-		}
+
+	struct Visitor {
+		Visitor(std::vector<std::pair<size_t, size_t>> &cell_data, std::vector<Cell> &cells, size_t cols) :
+			cell_data(cell_data), cells(cells), cols(cols), i(0), j(0) {}
+
+		void operator()(coord_t iy, coord_t ix) { cell_data[cells[iy*cols + ix].end++] = std::pair<size_t, size_t>(i, j); }
+
+		std::vector<std::pair<size_t, size_t>> &cell_data;
+		std::vector<Cell> 					   &cells;
+		size_t									cols;
+		size_t 									i;
+		size_t 									j;
+	} visitor(m_cell_data, m_cells, m_cols);
+
+	for (; visitor.i < m_contours.size(); ++ visitor.i) {
+		const Slic3r::Points &pts = *m_contours[visitor.i];
+		for (; visitor.j < pts.size(); ++ visitor.j)
+			this->visit_cells_intersecting_line(pts[visitor.j], pts[(visitor.j + 1 == pts.size()) ? 0 : visitor.j + 1], visitor);
 	}
 }
 
@@ -1360,28 +1251,6 @@ Polygons EdgeGrid::Grid::contours_simplified(coord_t offset, bool fill_holes) co
 	return out;
 }
 
-inline int segments_could_intersect(
-	const Slic3r::Point &ip1, const Slic3r::Point &ip2, 
-	const Slic3r::Point &jp1, const Slic3r::Point &jp2)
-{
-	Vec2i64 iv   = (ip2 - ip1).cast<int64_t>();
-	Vec2i64 vij1 = (jp1 - ip1).cast<int64_t>();
-	Vec2i64 vij2 = (jp2 - ip1).cast<int64_t>();
-	int64_t tij1 = cross2(iv, vij1);
-	int64_t tij2 = cross2(iv, vij2);
-	int     sij1 = (tij1 > 0) ? 1 : ((tij1 < 0) ? -1 : 0); // signum
-	int     sij2 = (tij2 > 0) ? 1 : ((tij2 < 0) ? -1 : 0);
-	return sij1 * sij2;
-}
-
-inline bool segments_intersect(
-	const Slic3r::Point &ip1, const Slic3r::Point &ip2, 
-	const Slic3r::Point &jp1, const Slic3r::Point &jp2)
-{
-	return segments_could_intersect(ip1, ip2, jp1, jp2) <= 0 && 
-		   segments_could_intersect(jp1, jp2, ip1, ip2) <= 0;
-}
-
 std::vector<std::pair<EdgeGrid::Grid::ContourEdge, EdgeGrid::Grid::ContourEdge>> EdgeGrid::Grid::intersecting_edges() const
 {
 	std::vector<std::pair<ContourEdge, ContourEdge>> out;
@@ -1405,7 +1274,7 @@ std::vector<std::pair<EdgeGrid::Grid::ContourEdge, EdgeGrid::Grid::ContourEdge>>
 					if (&ipts == &jpts && (&ip1 == &jp2 || &jp1 == &ip2))
 						// Segments of the same contour share a common vertex.
 						continue;
-					if (segments_intersect(ip1, ip2, jp1, jp2)) {
+					if (Geometry::segments_intersect(ip1, ip2, jp1, jp2)) {
 						// The two segments intersect. Add them to the output.
 						int jfirst = (&jpts < &ipts) || (&jpts == &ipts && jpt < ipt);
 						out.emplace_back(jfirst ? 
@@ -1440,7 +1309,7 @@ bool EdgeGrid::Grid::has_intersecting_edges() const
 					const Slic3r::Point  &jp1  = jpts[jpt];
 					const Slic3r::Point  &jp2  = jpts[(jpt + 1 == jpts.size()) ? 0 : jpt + 1];
 					if (! (&ipts == &jpts && (&ip1 == &jp2 || &jp1 == &ip2)) && 
-						segments_intersect(ip1, ip2, jp1, jp2))
+						Geometry::segments_intersect(ip1, ip2, jp1, jp2))
 						return true;
 				}
 			}
diff --git a/src/libslic3r/EdgeGrid.hpp b/src/libslic3r/EdgeGrid.hpp
index 7faafdb3e1..cad20e07bb 100644
--- a/src/libslic3r/EdgeGrid.hpp
+++ b/src/libslic3r/EdgeGrid.hpp
@@ -65,6 +65,145 @@ public:
 	std::vector<std::pair<ContourEdge, ContourEdge>> intersecting_edges() const;
 	bool 											 has_intersecting_edges() const;
 
+	template<typename FUNCTION> void visit_cells_intersecting_line(Slic3r::Point p1, Slic3r::Point p2, FUNCTION func) const
+	{
+		// End points of the line segment.
+		p1(0) -= m_bbox.min(0);
+		p1(1) -= m_bbox.min(1);
+		p2(0) -= m_bbox.min(0);
+		p2(1) -= m_bbox.min(1);
+		// Get the cells of the end points.
+		coord_t ix = p1(0) / m_resolution;
+		coord_t iy = p1(1) / m_resolution;
+		coord_t ixb = p2(0) / m_resolution;
+		coord_t iyb = p2(1) / m_resolution;
+		assert(ix >= 0 && size_t(ix) < m_cols);
+		assert(iy >= 0 && size_t(iy) < m_rows);
+		assert(ixb >= 0 && size_t(ixb) < m_cols);
+		assert(iyb >= 0 && size_t(iyb) < m_rows);
+		// Account for the end points.
+		func(iy, ix);
+		if (ix == ixb && iy == iyb)
+			// Both ends fall into the same cell.
+			return;
+		// Raster the centeral part of the line.
+		coord_t dx = std::abs(p2(0) - p1(0));
+		coord_t dy = std::abs(p2(1) - p1(1));
+		if (p1(0) < p2(0)) {
+			int64_t ex = int64_t((ix + 1)*m_resolution - p1(0)) * int64_t(dy);
+			if (p1(1) < p2(1)) {
+				// x positive, y positive
+				int64_t ey = int64_t((iy + 1)*m_resolution - p1(1)) * int64_t(dx);
+				do {
+					assert(ix <= ixb && iy <= iyb);
+					if (ex < ey) {
+						ey -= ex;
+						ex = int64_t(dy) * m_resolution;
+						ix += 1;
+					}
+					else if (ex == ey) {
+						ex = int64_t(dy) * m_resolution;
+						ey = int64_t(dx) * m_resolution;
+						ix += 1;
+						iy += 1;
+					}
+					else {
+						assert(ex > ey);
+						ex -= ey;
+						ey = int64_t(dx) * m_resolution;
+						iy += 1;
+					}
+					func(iy, ix);
+				} while (ix != ixb || iy != iyb);
+			}
+			else {
+				// x positive, y non positive
+				int64_t ey = int64_t(p1(1) - iy*m_resolution) * int64_t(dx);
+				do {
+					assert(ix <= ixb && iy >= iyb);
+					if (ex <= ey) {
+						ey -= ex;
+						ex = int64_t(dy) * m_resolution;
+						ix += 1;
+					}
+					else {
+						ex -= ey;
+						ey = int64_t(dx) * m_resolution;
+						iy -= 1;
+					}
+					func(iy, ix);
+				} while (ix != ixb || iy != iyb);
+			}
+		}
+		else {
+			int64_t ex = int64_t(p1(0) - ix*m_resolution) * int64_t(dy);
+			if (p1(1) < p2(1)) {
+				// x non positive, y positive
+				int64_t ey = int64_t((iy + 1)*m_resolution - p1(1)) * int64_t(dx);
+				do {
+					assert(ix >= ixb && iy <= iyb);
+					if (ex < ey) {
+						ey -= ex;
+						ex = int64_t(dy) * m_resolution;
+						ix -= 1;
+					}
+					else {
+						assert(ex >= ey);
+						ex -= ey;
+						ey = int64_t(dx) * m_resolution;
+						iy += 1;
+					}
+					func(iy, ix);
+				} while (ix != ixb || iy != iyb);
+			}
+			else {
+				// x non positive, y non positive
+				int64_t ey = int64_t(p1(1) - iy*m_resolution) * int64_t(dx);
+				do {
+					assert(ix >= ixb && iy >= iyb);
+					if (ex < ey) {
+						ey -= ex;
+						ex = int64_t(dy) * m_resolution;
+						ix -= 1;
+					}
+					else if (ex == ey) {
+						// The lower edge of a grid cell belongs to the cell.
+						// Handle the case where the ray may cross the lower left corner of a cell in a general case,
+						// or a left or lower edge in a degenerate case (horizontal or vertical line).
+						if (dx > 0) {
+							ex = int64_t(dy) * m_resolution;
+							ix -= 1;
+						}
+						if (dy > 0) {
+							ey = int64_t(dx) * m_resolution;
+							iy -= 1;
+						}
+					}
+					else {
+						assert(ex > ey);
+						ex -= ey;
+						ey = int64_t(dx) * m_resolution;
+						iy -= 1;
+					}
+					func(iy, ix);
+				} while (ix != ixb || iy != iyb);
+			}
+		}
+	}
+
+	std::pair<std::vector<std::pair<size_t, size_t>>::const_iterator, std::vector<std::pair<size_t, size_t>>::const_iterator> cell_data_range(coord_t row, coord_t col) const
+	{
+		const EdgeGrid::Grid::Cell &cell = m_cells[row * m_cols + col];
+		return std::make_pair(m_cell_data.begin() + cell.begin, m_cell_data.begin() + cell.end);
+	}
+
+	std::pair<const Slic3r::Point&, const Slic3r::Point&> segment(const std::pair<size_t, size_t> &contour_and_segment_idx) const
+	{
+		const Slic3r::Points &ipts = *m_contours[contour_and_segment_idx.first];
+		size_t ipt = contour_and_segment_idx.second;
+		return std::pair<const Slic3r::Point&, const Slic3r::Point&>(ipts[ipt], ipts[(ipt + 1 == ipts.size()) ? 0 : ipt + 1]);
+	}
+
 protected:
 	struct Cell {
 		Cell() : begin(0), end(0) {}
diff --git a/src/libslic3r/Geometry.hpp b/src/libslic3r/Geometry.hpp
index dca1872d82..eec2673227 100644
--- a/src/libslic3r/Geometry.hpp
+++ b/src/libslic3r/Geometry.hpp
@@ -111,6 +111,29 @@ inline bool segment_segment_intersection(const Vec2d &p1, const Vec2d &v1, const
     return true;
 }
 
+
+inline int segments_could_intersect(
+	const Slic3r::Point &ip1, const Slic3r::Point &ip2, 
+	const Slic3r::Point &jp1, const Slic3r::Point &jp2)
+{
+	Vec2i64 iv   = (ip2 - ip1).cast<int64_t>();
+	Vec2i64 vij1 = (jp1 - ip1).cast<int64_t>();
+	Vec2i64 vij2 = (jp2 - ip1).cast<int64_t>();
+	int64_t tij1 = cross2(iv, vij1);
+	int64_t tij2 = cross2(iv, vij2);
+	int     sij1 = (tij1 > 0) ? 1 : ((tij1 < 0) ? -1 : 0); // signum
+	int     sij2 = (tij2 > 0) ? 1 : ((tij2 < 0) ? -1 : 0);
+	return sij1 * sij2;
+}
+
+inline bool segments_intersect(
+	const Slic3r::Point &ip1, const Slic3r::Point &ip2, 
+	const Slic3r::Point &jp1, const Slic3r::Point &jp2)
+{
+	return segments_could_intersect(ip1, ip2, jp1, jp2) <= 0 && 
+		   segments_could_intersect(jp1, jp2, ip1, ip2) <= 0;
+}
+
 Pointf3s convex_hull(Pointf3s points);
 Polygon convex_hull(Points points);
 Polygon convex_hull(const Polygons &polygons);
diff --git a/src/libslic3r/PolygonTrimmer.cpp b/src/libslic3r/PolygonTrimmer.cpp
new file mode 100644
index 0000000000..3e3c9b4982
--- /dev/null
+++ b/src/libslic3r/PolygonTrimmer.cpp
@@ -0,0 +1,56 @@
+#include "PolygonTrimmer.hpp"
+#include "EdgeGrid.hpp"
+#include "Geometry.hpp"
+
+namespace Slic3r {
+
+TrimmedLoop trim_loop(const Polygon &loop, const EdgeGrid::Grid &grid)
+{
+	assert(! loop.empty());
+	assert(loop.size() >= 2);
+
+	TrimmedLoop out;
+
+	if (loop.size() >= 2) {
+		size_t cnt = loop.points.size();
+
+		struct Visitor {
+			Visitor(const EdgeGrid::Grid &grid, const Slic3r::Point *pt_prev, const Slic3r::Point *pt_this) : grid(grid), pt_prev(pt_prev), pt_this(pt_this) {}
+
+			void operator()(coord_t iy, coord_t ix) {
+				// Called with a row and colum of the grid cell, which is intersected by a line.
+				auto cell_data_range = grid.cell_data_range(iy, ix);
+				for (auto it_contour_and_segment = cell_data_range.first; it_contour_and_segment != cell_data_range.second; ++ it_contour_and_segment) {
+					// End points of the line segment and their vector.
+					auto segment = grid.segment(*it_contour_and_segment);
+					if (Geometry::segments_intersect(segment.first, segment.second, *pt_prev, *pt_this)) {
+						// The two segments intersect. Add them to the output.
+					}
+				}
+			}
+
+			const EdgeGrid::Grid &grid;
+			const Slic3r::Point  *pt_this;
+			const Slic3r::Point  *pt_prev;
+		} visitor(grid, &loop.points.back(), nullptr);
+
+		for (const Point &pt_this : loop.points) {
+			visitor.pt_this = &pt_this;
+			grid.visit_cells_intersecting_line(*visitor.pt_prev, pt_this, visitor);
+			visitor.pt_prev = &pt_this;
+		}
+	}
+
+	return out;
+}
+
+std::vector<TrimmedLoop> trim_loops(const Polygons &loops, const EdgeGrid::Grid &grid)
+{
+	std::vector<TrimmedLoop> out;
+	out.reserve(loops.size());
+	for (const Polygon &loop : loops)
+		out.emplace_back(trim_loop(loop, grid));
+	return out;
+}
+
+}
diff --git a/src/libslic3r/PolygonTrimmer.hpp b/src/libslic3r/PolygonTrimmer.hpp
new file mode 100644
index 0000000000..b2a780be91
--- /dev/null
+++ b/src/libslic3r/PolygonTrimmer.hpp
@@ -0,0 +1,31 @@
+#ifndef slic3r_PolygonTrimmer_hpp_
+#define slic3r_PolygonTrimmer_hpp_
+
+#include "libslic3r.h"
+#include <vector>
+#include <string>
+#include "Line.hpp"
+#include "MultiPoint.hpp"
+#include "Polyline.hpp"
+
+namespace Slic3r {
+
+namespace EdgeGrid {
+	class Grid;
+}
+
+struct TrimmedLoop
+{
+	std::vector<Point> 			points;
+	// Number of points per segment. Empty if the loop is 
+	std::vector<unsigned int> 	segments;
+
+	bool 	is_trimmed() const { return ! segments.empty(); }
+};
+
+TrimmedLoop trim_loop(const Polygon &loop, const EdgeGrid::Grid &grid);
+std::vector<TrimmedLoop> trim_loops(const Polygons &loops, const EdgeGrid::Grid &grid);
+
+} // namespace Slic3r
+
+#endif /* slic3r_PolygonTrimmer_hpp_ */