diff --git a/xs/CMakeLists.txt b/xs/CMakeLists.txt
index 63b99a835..2bf28ec01 100644
--- a/xs/CMakeLists.txt
+++ b/xs/CMakeLists.txt
@@ -74,6 +74,8 @@ add_library(libslic3r STATIC
     ${LIBDIR}/libslic3r/Fill/FillRectilinear2.hpp
     ${LIBDIR}/libslic3r/Fill/FillRectilinear3.cpp
     ${LIBDIR}/libslic3r/Fill/FillRectilinear3.hpp
+    ${LIBDIR}/libslic3r/Fill/FillSmooth.cpp
+    ${LIBDIR}/libslic3r/Fill/FillSmooth.hpp
     ${LIBDIR}/libslic3r/Flow.cpp
     ${LIBDIR}/libslic3r/Flow.hpp
     ${LIBDIR}/libslic3r/Format/3mf.cpp
diff --git a/xs/src/libslic3r/ExtrusionEntityCollection.cpp b/xs/src/libslic3r/ExtrusionEntityCollection.cpp
index 4513139e2..e99c170a4 100644
--- a/xs/src/libslic3r/ExtrusionEntityCollection.cpp
+++ b/xs/src/libslic3r/ExtrusionEntityCollection.cpp
@@ -207,6 +207,45 @@ ExtrusionEntityCollection::flatten() const
     return coll;
 }
 
+/* Returns a vector of chained (new) pointers to all non-collection items contained in this one */
+void
+ExtrusionEntityCollection::flattenIfSortable(ExtrusionEntityCollection* retval) const
+{
+	if (no_sort){
+		ExtrusionEntityCollection *unsortable = new ExtrusionEntityCollection(*this);
+		retval->append(*unsortable);
+		unsortable->entities.clear();
+		for (ExtrusionEntitiesPtr::const_iterator it = this->entities.begin(); it != this->entities.end(); ++it) {
+			if ((*it)->is_collection()) {
+				ExtrusionEntityCollection* collection = dynamic_cast<ExtrusionEntityCollection*>(*it);
+				collection->flattenIfSortable(unsortable);
+			}
+			else {
+				unsortable->append(**it);
+			}
+		}
+	}
+	else{
+		for (ExtrusionEntitiesPtr::const_iterator it = this->entities.begin(); it != this->entities.end(); ++it) {
+			if ((*it)->is_collection()) {
+				ExtrusionEntityCollection* collection = dynamic_cast<ExtrusionEntityCollection*>(*it);
+				retval->append(collection->flattenIfSortable().entities);
+			}
+			else {
+				retval->append(**it);
+			}
+		}
+	}
+}
+
+ExtrusionEntityCollection
+ExtrusionEntityCollection::flattenIfSortable() const
+{
+	ExtrusionEntityCollection coll;
+	this->flattenIfSortable(&coll);
+	return coll;
+}
+
 double
 ExtrusionEntityCollection::min_mm3_per_mm() const
 {
diff --git a/xs/src/libslic3r/ExtrusionEntityCollection.hpp b/xs/src/libslic3r/ExtrusionEntityCollection.hpp
index 03bd2ba97..1fdea25f1 100644
--- a/xs/src/libslic3r/ExtrusionEntityCollection.hpp
+++ b/xs/src/libslic3r/ExtrusionEntityCollection.hpp
@@ -77,7 +77,9 @@ public:
         { Polygons out; this->polygons_covered_by_spacing(out, scaled_epsilon); return out; }
     size_t items_count() const;
     void flatten(ExtrusionEntityCollection* retval) const;
-    ExtrusionEntityCollection flatten() const;
+	ExtrusionEntityCollection flatten() const;
+	void flattenIfSortable(ExtrusionEntityCollection* retval) const;
+	ExtrusionEntityCollection flattenIfSortable() const;
     double min_mm3_per_mm() const;
 
     // Following methods shall never be called on an ExtrusionEntityCollection.
diff --git a/xs/src/libslic3r/Fill/Fill.cpp b/xs/src/libslic3r/Fill/Fill.cpp
index fcb12c47e..b0a80dbeb 100644
--- a/xs/src/libslic3r/Fill/Fill.cpp
+++ b/xs/src/libslic3r/Fill/Fill.cpp
@@ -228,9 +228,6 @@ void make_fill(LayerRegion &layerm, ExtrusionEntityCollection &out)
         params.density = 0.01 * density;
 //        params.dont_adjust = true;
         params.dont_adjust = false;
-        Polylines polylines = f->fill_surface(&surface, params);
-        if (polylines.empty())
-            continue;
 
         // calculate actual flow from spacing (which might have been adjusted by the infill
         // pattern generator)
@@ -244,22 +241,10 @@ void make_fill(LayerRegion &layerm, ExtrusionEntityCollection &out)
 		
 		float flow_percent = 1;
 		if(surface.is_overBridge()){
-			flow_percent = layerm.region()->config.over_bridge_flow_ratio;
+			params.flow_mult = layerm.region()->config.over_bridge_flow_ratio;
 		}
-
-        // Save into layer.
-        auto *eec = new ExtrusionEntityCollection();
-        out.entities.push_back(eec);
-        // Only concentric fills are not sorted.
-        eec->no_sort = f->no_sort();
-        extrusion_entities_append_paths(
-            eec->entities, STDMOVE(polylines),
-            is_bridge ?
-                erBridgeInfill :
-                (surface.is_solid() ?
-                    ((surface.surface_type == stTop) ? erTopSolidInfill : erSolidInfill) :
-                    erInternalInfill),
-            flow.mm3_per_mm()*flow_percent, flow.width*flow_percent, flow.height);
+		
+        f->fill_surface_extrusion(&surface, params, flow, out);
     }
 
     // add thin fill regions
diff --git a/xs/src/libslic3r/Fill/FillBase.cpp b/xs/src/libslic3r/Fill/FillBase.cpp
index 88645b3d9..5b4d2e195 100644
--- a/xs/src/libslic3r/Fill/FillBase.cpp
+++ b/xs/src/libslic3r/Fill/FillBase.cpp
@@ -3,6 +3,7 @@
 #include "../ClipperUtils.hpp"
 #include "../Surface.hpp"
 #include "../PrintConfig.hpp"
+#include "../ExtrusionEntityCollection.hpp"
 
 #include "FillBase.hpp"
 #include "FillConcentric.hpp"
@@ -13,6 +14,7 @@
 #include "FillRectilinear.hpp"
 #include "FillRectilinear2.hpp"
 #include "FillRectilinear3.hpp"
+#include "FillSmooth.hpp"
 
 namespace Slic3r {
 
@@ -34,6 +36,7 @@ Fill* Fill::new_from_type(const InfillPattern type)
     case ipArchimedeanChords:   return new FillArchimedeanChords();
     case ipHilbertCurve:        return new FillHilbertCurve();
     case ipOctagramSpiral:      return new FillOctagramSpiral();
+	case ipSmooth:              return new FillSmooth();
     default: CONFESS("unknown type"); return nullptr;
     }
 }
@@ -130,4 +133,25 @@ std::pair<float, Point> Fill::_infill_direction(const Surface *surface) const
     return std::pair<float, Point>(out_angle, out_shift);
 }
 
+void Fill::fill_surface_extrusion(const Surface *surface, const FillParams &params, const Flow &flow, ExtrusionEntityCollection &out ){
+    Polylines polylines = this->fill_surface(surface, params);
+    if (polylines.empty())
+        return;
+
+    // Save into layer.
+    auto *eec = new ExtrusionEntityCollection();
+    out.entities.push_back(eec);
+    // Only concentric fills are not sorted.
+    eec->no_sort = this->no_sort();
+    extrusion_entities_append_paths(
+        eec->entities, STDMOVE(polylines),
+        flow.bridge ?
+            erBridgeInfill :
+            (surface->is_solid() ?
+                ((surface->is_top()) ? erTopSolidInfill : erSolidInfill) :
+                erInternalInfill),
+				flow.mm3_per_mm() * params.flow_mult, flow.width * params.flow_mult, flow.height);
+    
+}
+
 } // namespace Slic3r
diff --git a/xs/src/libslic3r/Fill/FillBase.hpp b/xs/src/libslic3r/Fill/FillBase.hpp
index 62d18e518..9048f9e90 100644
--- a/xs/src/libslic3r/Fill/FillBase.hpp
+++ b/xs/src/libslic3r/Fill/FillBase.hpp
@@ -9,6 +9,7 @@
 #include "../libslic3r.h"
 #include "../BoundingBox.hpp"
 #include "../PrintConfig.hpp"
+#include "../Flow.hpp"
 
 namespace Slic3r {
 
@@ -20,12 +21,16 @@ struct FillParams
         memset(this, 0, sizeof(FillParams));
         // Adjustment does not work.
         dont_adjust = true;
+		flow_mult = 1.f;
     }
 
     bool        full_infill() const { return density > 0.9999f; }
 
-    // Fill density, fraction in <0, 1>
-    float       density;
+	// Fill density, fraction in <0, 1>
+	float       density;
+
+	// Fill extruding flow multiplier, fraction in <0, 1>. Used by FillSmooth
+	float       flow_mult;
 
     // Don't connect the fill lines around the inner perimeter.
     bool        dont_connect;
@@ -75,6 +80,9 @@ public:
     // Do not sort the fill lines to optimize the print head path?
     virtual bool no_sort() const { return false; }
 
+    // This method have to fill the ExtrusionEntityCollection. It call fill_surface by default
+    virtual void fill_surface_extrusion(const Surface *surface, const FillParams &params, const Flow &flow, ExtrusionEntityCollection &out );
+	
     // Perform the fill.
     virtual Polylines fill_surface(const Surface *surface, const FillParams &params);
 
diff --git a/xs/src/libslic3r/Fill/FillSmooth.cpp b/xs/src/libslic3r/Fill/FillSmooth.cpp
new file mode 100644
index 000000000..6c956435f
--- /dev/null
+++ b/xs/src/libslic3r/Fill/FillSmooth.cpp
@@ -0,0 +1,160 @@
+#include "../ClipperUtils.hpp"
+#include "../PolylineCollection.hpp"
+#include "../ExtrusionEntityCollection.hpp"
+#include "../Surface.hpp"
+#include <cmath>
+#include <algorithm>
+#include <iostream>
+
+#include "FillSmooth.hpp"
+
+namespace Slic3r {
+
+Polylines FillSmooth::fill_surface(const Surface *surface, const FillParams &params)
+{
+    //ERROR: you shouldn't call that. Default to the rectilinear one.
+    printf("FillSmooth::fill_surface() : you call the wrong method (fill_surface instead of fill_surface_extrusion).\n");
+    Polylines polylines_out;
+    return polylines_out;
+}
+
+
+void FillSmooth::fill_surface_extrusion(const Surface *surface, const FillParams &params, const Flow &flow, ExtrusionEntityCollection &out )
+{
+	coordf_t init_spacing = this->spacing;
+	
+    printf("FillSmooth::fill_surface() : you call the right method (fill_surface instead of fill_surface_extrusion).\n");
+    //second pass with half layer width
+    FillParams params1 = params;
+    FillParams params2 = params;
+    FillParams params3 = params;
+	params1.density *= percentWidth[0];
+	params2.density *= percentWidth[1];
+	params3.density *= percentWidth[2];
+//    Polylines polylines_layer1;
+//    Polylines polylines_layer2; 
+//    Polylines polylines_layer3; 
+	
+	 //a small under-overlap to prevent over-extrudion on thin surfaces (i.e. remove the overlap)
+	Surface surfaceNoOverlap(*surface);
+	//remove the overlap (prevent over-extruding)
+	ExPolygons offsetPloys = offset2_ex(surfaceNoOverlap.expolygon, -scale_(this->overlap)*0.9, 0);
+	
+	if(offsetPloys.size() == 1) surfaceNoOverlap.expolygon = offsetPloys[0];
+	//TODO: recursive if multiple polys instead of failing
+	
+	//if (! fill_surface_by_lines(&surfaceNoOverlap/* */, params1, anglePass[0], 0.f, polylines_layer1) ||
+	//	(nbPass>1 && !fill_surface_by_lines(surface, params2, anglePass[1], 0.f, polylines_layer2)) ||
+	//	(nbPass>2 && !fill_surface_by_lines(surface, params3, anglePass[2], 0.f, polylines_layer3))) {
+	//	printf("FillSmooth::fill_surface() failed to fill a region.\n");
+	//}
+	/*
+	std::cout<<"polylines_layer1 size ="<<polylines_layer1.size()<<" \n";
+	std::cout<<"polylines_layer2 size ="<<polylines_layer2.size()<<" \n";
+	std::cout<<"polylines_layer3 size ="<<polylines_layer3.size()<<" \n";*/
+
+	//if (polylines_layer1.empty() && polylines_layer2.empty() && polylines_layer3.empty())
+	//	return;
+	
+	//create root node
+    ExtrusionEntityCollection *eecroot = new ExtrusionEntityCollection();
+    //you don't want to sort the extrusions: big infill first, small second
+    eecroot->no_sort = true;
+
+	ExtrusionEntityCollection *eec;
+	
+	// first infill
+	std::unique_ptr<Fill> f1 = std::unique_ptr<Fill>(Fill::new_from_type(fillPattern[0]));
+	f1->bounding_box = this->bounding_box;
+	f1->spacing = init_spacing;
+	f1->layer_id = this->layer_id;
+	f1->z = this->z;
+	f1->angle = anglePass[0];
+	// Maximum length of the perimeter segment linking two infill lines.
+	f1->link_max_length = this->link_max_length;
+	// Used by the concentric infill pattern to clip the loops to create extrusion paths.
+	f1->loop_clipping = this->loop_clipping;
+	Polylines polylines_layer1 = f1->fill_surface(surface, params1);
+
+	if (!polylines_layer1.empty()){
+		eec = new ExtrusionEntityCollection();
+		eecroot->entities.push_back(eec);
+		eec->no_sort = false; //can be sorted inside the pass
+		extrusion_entities_append_paths(
+			eec->entities, STDMOVE(polylines_layer1),
+			flow.bridge ? erBridgeInfill : rolePass[0],
+			flow.mm3_per_mm()*percentFlow[0], (float)flow.width*percentFlow[0], (float)flow.height*0.9);
+			//reduced flow width & height for a better view (it's only a gui thing)
+	}
+	
+	//second infill
+	if (nbPass > 1){
+
+		std::unique_ptr<Fill> f2 = std::unique_ptr<Fill>(Fill::new_from_type(fillPattern[1]));
+		f2->bounding_box = this->bounding_box;
+		f2->spacing = init_spacing;
+		f2->layer_id = this->layer_id;
+		f2->z = this->z;
+		f2->angle = anglePass[1];
+		// Maximum length of the perimeter segment linking two infill lines.
+		f2->link_max_length = this->link_max_length;
+		// Used by the concentric infill pattern to clip the loops to create extrusion paths.
+		f2->loop_clipping = this->loop_clipping;
+		Polylines polylines_layer2 = f2->fill_surface(&surfaceNoOverlap, params2);
+
+		if (fillPattern[2] == InfillPattern::ipRectilinear && polylines_layer2[0].points.size() > 3){
+			polylines_layer2[0].points.erase(polylines_layer2[0].points.begin());
+			polylines_layer2[polylines_layer2.size() - 1].points.pop_back();
+		}
+		if (!polylines_layer2.empty()){
+
+			// Save into layer smoothing path.
+			eec = new ExtrusionEntityCollection();
+			eecroot->entities.push_back(eec);
+			eec->no_sort = false;
+			// print thin
+			extrusion_entities_append_paths(
+				eec->entities, STDMOVE(polylines_layer2),
+				rolePass[1],
+				flow.mm3_per_mm()*percentFlow[1], (float)flow.width*(percentFlow[1] < 0.1 ? 0.1 : percentFlow[1]), (float)flow.height);
+		}
+	}
+	
+	// third infill
+	if (nbPass > 2){
+		std::unique_ptr<Fill> f3 = std::unique_ptr<Fill>(Fill::new_from_type(fillPattern[0]));
+		f3->bounding_box = this->bounding_box;
+		f3->spacing = init_spacing;
+		f3->layer_id = this->layer_id;
+		f3->z = this->z;
+		f3->angle = anglePass[2];
+		// Maximum length of the perimeter segment linking two infill lines.
+		f3->link_max_length = this->link_max_length;
+		// Used by the concentric infill pattern to clip the loops to create extrusion paths.
+		f3->loop_clipping = this->loop_clipping;
+		Polylines polylines_layer3 = f3->fill_surface(&surfaceNoOverlap, params1);
+
+		//remove some points that are not inside the area
+		if (fillPattern[2] == InfillPattern::ipRectilinear && polylines_layer3[0].points.size() > 3){
+			polylines_layer3[0].points.erase(polylines_layer3[0].points.begin());
+			polylines_layer3[polylines_layer3.size() - 1].points.pop_back();
+		}
+		if (!polylines_layer3.empty()){
+			// Save into layer smoothing path. layer 3
+			eec = new ExtrusionEntityCollection();
+			eecroot->entities.push_back(eec);
+			eec->no_sort = false;
+			// print thin
+			extrusion_entities_append_paths(
+				eec->entities, STDMOVE(polylines_layer3),
+				rolePass[2], //slow (if last)
+				flow.mm3_per_mm()*percentFlow[2], (float)flow.width*(percentFlow[2] < 0.1 ? 0.1 : percentFlow[2]), (float)flow.height);
+		}
+	}
+
+	if (!eecroot->entities.empty())
+		out.entities.push_back(eecroot);
+    
+}
+
+} // namespace Slic3r
diff --git a/xs/src/libslic3r/Fill/FillSmooth.hpp b/xs/src/libslic3r/Fill/FillSmooth.hpp
new file mode 100644
index 000000000..f4a7b3a50
--- /dev/null
+++ b/xs/src/libslic3r/Fill/FillSmooth.hpp
@@ -0,0 +1,58 @@
+#ifndef slic3r_FillSmooth_hpp_
+#define slic3r_FillSmooth_hpp_
+
+#include "../libslic3r.h"
+
+#include "FillBase.hpp"
+
+namespace Slic3r {
+
+class FillSmooth : public Fill
+{
+public:
+    FillSmooth() {
+		nbPass = 2;
+		anglePass[0] = float(M_PI/4);
+		anglePass[1] = -float(M_PI/4);
+		anglePass[2] = 0;
+		fillPattern[0] = InfillPattern::ipRectilinear;
+		fillPattern[1] = InfillPattern::ipRectilinear;
+		fillPattern[2] = InfillPattern::ipRectilinear;
+		rolePass[0] = erSolidInfill;
+		rolePass[1] = erTopSolidInfill;
+		rolePass[2] = erSolidInfill;
+		percentWidth[0] = 0.9;
+		percentWidth[1] = 2;
+		percentWidth[2] = 1.0;
+		percentFlow[0] = 0.7/percentWidth[0]; //* 1.25 => 0.9
+		percentFlow[1] = 0.3/percentWidth[1]; //*1.25 => 0.35
+		percentFlow[2] = 0.0/percentWidth[2];
+		// percentWidth[0] = 2.0;
+		// percentWidth[1] = 0.6;
+		// percentWidth[2] = 1.0;
+		// percentFlow[0] = 0.65;
+		// percentFlow[1] = 0.0;
+		// percentFlow[2] = 0.0;
+//		(extrusion mult => 0.9 + 0.15*2 = 1.2)
+		double extrusionMult = 1.0;
+		percentFlow[0] *= extrusionMult;
+		percentFlow[1] *= extrusionMult;
+		percentFlow[2] *= extrusionMult;
+	}
+    virtual Fill* clone() const { return new FillSmooth(*this); }
+
+	virtual Polylines fill_surface(const Surface *surface, const FillParams &params);
+    virtual void fill_surface_extrusion(const Surface *surface, const FillParams &params, const Flow &flow, ExtrusionEntityCollection &out );
+	
+protected:
+	int nbPass=2;
+	double percentWidth[3];
+	double percentFlow[3];
+	float anglePass[3];
+	ExtrusionRole rolePass[3];
+	InfillPattern fillPattern[3];
+};
+
+} // namespace Slic3r
+
+#endif // slic3r_FillSmooth_hpp_
diff --git a/xs/src/libslic3r/GCode.cpp b/xs/src/libslic3r/GCode.cpp
index 8ad479532..6f6252f29 100644
--- a/xs/src/libslic3r/GCode.cpp
+++ b/xs/src/libslic3r/GCode.cpp
@@ -1271,8 +1271,9 @@ void GCode::process_layer(
                             point_inside_surface(i, fill->first_point())) {
                             if (islands[i].by_region.empty())
                                 islands[i].by_region.assign(print.regions.size(), ObjectByExtruder::Island::Region());
-                            islands[i].by_region[region_id].infills.append(fill->entities);
-                            break;
+							//don't do fill->entities because it will discard no_sort
+							islands[i].by_region[region_id].infills.append(fill->flattenIfSortable().entities);
+							break;
                         }
                 }
             } // for regions
@@ -2001,14 +2002,34 @@ std::string GCode::extrude_infill(const Print &print, const std::vector<ObjectBy
     for (const ObjectByExtruder::Island::Region &region : by_region) {
         m_config.apply(print.regions[&region - &by_region.front()]->config);
 		ExtrusionEntityCollection chained = region.infills.chained_path_from(m_last_pos, false);
-        for (ExtrusionEntity *fill : chained.entities) {
-            auto *eec = dynamic_cast<ExtrusionEntityCollection*>(fill);
-            if (eec) {
-				ExtrusionEntityCollection chained2 = eec->chained_path_from(m_last_pos, false);
-				for (ExtrusionEntity *ee : chained2.entities)
-                    gcode += this->extrude_entity(*ee, "infill");
-            } else
-                gcode += this->extrude_entity(*fill, "infill");
+		gcode += extrude_infill(print, chained);
+	}
+	return gcode;
+}
+
+//recursive algorithm to explore the collection tree
+std::string GCode::extrude_infill(const Print &print, const ExtrusionEntityCollection &collection)
+{
+	std::string gcode;
+
+	ExtrusionEntityCollection chained;
+	if (collection.no_sort) chained = collection;
+	else chained = collection.chained_path_from(m_last_pos, false);
+	for (ExtrusionEntity *fill : chained.entities) {
+		auto *eec = dynamic_cast<ExtrusionEntityCollection*>(fill);
+		if (eec) {
+			std::cout << "recursive infill with role: " << fill->role() << " : " << (fill->role() == ExtrusionRole::erBridgeInfill) << "\n";
+			gcode += extrude_infill(print, *eec);
+		}
+		else {
+			std::cout << "extrude infill with role: " << fill->role() << " : " << (fill->role() == ExtrusionRole::erBridgeInfill) << "\n";
+			if (/*print.config.disable_fan_top_layers.value && */fill->role() == ExtrusionRole::erTopSolidInfill){ //TODO: add && params.get(disable_fan_top_layers)
+				// gcode += ";_DISABLE_FAN_START\n";
+			}
+			gcode += this->extrude_entity(*fill, "infill");
+			if (/*print.config.disable_fan_top_layers.value && */fill->role() == ExtrusionRole::erTopSolidInfill){ //TODO: add && params.get(disable_fan_top_layers)
+				// gcode += ";_DISABLE_FAN_END\n";
+			}
         }
     }
     return gcode;
diff --git a/xs/src/libslic3r/GCode.hpp b/xs/src/libslic3r/GCode.hpp
index 968cd14de..fbfa171d8 100644
--- a/xs/src/libslic3r/GCode.hpp
+++ b/xs/src/libslic3r/GCode.hpp
@@ -221,7 +221,8 @@ protected:
     };
     std::string     extrude_perimeters(const Print &print, const std::vector<ObjectByExtruder::Island::Region> &by_region, std::unique_ptr<EdgeGrid::Grid> &lower_layer_edge_grid);
     std::string     extrude_infill(const Print &print, const std::vector<ObjectByExtruder::Island::Region> &by_region);
-    std::string     extrude_support(const ExtrusionEntityCollection &support_fills);
+	std::string     extrude_infill(const Print &print, const ExtrusionEntityCollection &collection); // recursive extrude_infill
+	std::string     extrude_support(const ExtrusionEntityCollection &support_fills);
 
     std::string     travel_to(const Point &point, ExtrusionRole role, std::string comment);
     bool            needs_retraction(const Polyline &travel, ExtrusionRole role = erNone);
diff --git a/xs/src/libslic3r/PrintConfig.cpp b/xs/src/libslic3r/PrintConfig.cpp
index b93eafd9a..d6a83ab43 100644
--- a/xs/src/libslic3r/PrintConfig.cpp
+++ b/xs/src/libslic3r/PrintConfig.cpp
@@ -264,11 +264,13 @@ PrintConfigDef::PrintConfigDef()
     def->enum_values.push_back("hilbertcurve");
     def->enum_values.push_back("archimedeanchords");
     def->enum_values.push_back("octagramspiral");
+    def->enum_values.push_back("smooth");
     def->enum_labels.push_back("Rectilinear");
     def->enum_labels.push_back("Concentric");
     def->enum_labels.push_back("Hilbert Curve");
     def->enum_labels.push_back("Archimedean Chords");
     def->enum_labels.push_back("Octagram Spiral");
+    def->enum_labels.push_back("Ironing");
     // solid_fill_pattern is an obsolete equivalent to top_fill_pattern/bottom_fill_pattern.
     def->aliases.push_back("solid_fill_pattern");
     def->default_value = new ConfigOptionEnum<InfillPattern>(ipRectilinear);
diff --git a/xs/src/libslic3r/PrintConfig.hpp b/xs/src/libslic3r/PrintConfig.hpp
index e9164aba1..66c297d62 100644
--- a/xs/src/libslic3r/PrintConfig.hpp
+++ b/xs/src/libslic3r/PrintConfig.hpp
@@ -29,7 +29,7 @@ enum GCodeFlavor {
 
 enum InfillPattern {
     ipRectilinear, ipGrid, ipTriangles, ipStars, ipCubic, ipLine, ipConcentric, ipHoneycomb, ip3DHoneycomb,
-    ipGyroid, ipHilbertCurve, ipArchimedeanChords, ipOctagramSpiral,
+    ipGyroid, ipHilbertCurve, ipArchimedeanChords, ipOctagramSpiral, ipSmooth,
 };
 
 enum SupportMaterialPattern {
@@ -77,6 +77,7 @@ template<> inline t_config_enum_values& ConfigOptionEnum<InfillPattern>::get_enu
         keys_map["hilbertcurve"]        = ipHilbertCurve;
         keys_map["archimedeanchords"]   = ipArchimedeanChords;
         keys_map["octagramspiral"]      = ipOctagramSpiral;
+        keys_map["smooth"]      = ipSmooth;
     }
     return keys_map;
 }