diff --git a/Makefile b/Makefile
index 3968ed49..e59ef88e 100644
--- a/Makefile
+++ b/Makefile
@@ -58,7 +58,7 @@ C = $(wildcard *.c) $(wildcard *.cpp)
 INCLUDES = -I/usr/local/include -I.
 LIBS = -L/usr/local/lib
 
-tippecanoe: geojson.o jsonpull/jsonpull.o tile.o pool.o mbtiles.o geometry.o projection.o memfile.o mvt.o serial.o main.o text.o dirtiles.o pmtiles_file.o plugin.o read_json.o write_json.o geobuf.o flatgeobuf.o evaluator.o geocsv.o csv.o geojson-loop.o json_logger.o visvalingam.o compression.o clip.o sort.o
+tippecanoe: geojson.o jsonpull/jsonpull.o tile.o pool.o mbtiles.o geometry.o projection.o memfile.o mvt.o serial.o main.o text.o dirtiles.o pmtiles_file.o plugin.o read_json.o write_json.o geobuf.o flatgeobuf.o evaluator.o geocsv.o csv.o geojson-loop.o json_logger.o visvalingam.o compression.o clip.o sort.o polygon.o
 	$(CXX) $(PG) $(LIBS) $(FINAL_FLAGS) $(CXXFLAGS) -o $@ $^ $(LDFLAGS) -lm -lz -lsqlite3 -lpthread
 
 tippecanoe-enumerate: enumerate.o
diff --git a/polygon.cpp b/polygon.cpp
new file mode 100644
index 00000000..3e82866f
--- /dev/null
+++ b/polygon.cpp
@@ -0,0 +1,52 @@
+#include "geometry.hpp"
+
+struct point {
+	double x;
+	double y;
+
+	point(double x_, double y_)
+	    : x(x_), y(y_) {
+	}
+};
+
+drawvec clean_polygon(drawvec const &geom, int z, int detail) {
+	double scale = 1LL << (-(32 - detail - z));
+
+	// decompose polygon rings into segments
+
+	std::vector<std::pair<point, point>> segments;
+
+	for (size_t i = 0; i < geom.size(); i++) {
+		if (geom[i].op == VT_MOVETO) {
+			size_t j;
+
+			for (j = i + 1; j < geom.size(); j++) {
+				if (geom[i].op != VT_LINETO) {
+					break;
+				}
+			}
+
+			for (size_t k = i; k + 1 < j; k++) {
+				std::pair<point, point> segment = std::make_pair(
+					point(geom[k].x / scale, geom[k].y / scale),
+					point(geom[k + 1].x / scale, geom[k + 1].y / scale));
+
+				segments.push_back(segment);
+			}
+
+			i = j - 1;
+		}
+	}
+
+	// snap-round intersecting segments
+
+	// remove duplicate segments with opposite windings
+
+	// reassemble segments into rings
+
+	// remove collinear points?
+
+	// determine ring nesting
+
+	return drawvec();
+}