diff --git a/README.md b/README.md
index 167c3f33..2c71475d 100644
--- a/README.md
+++ b/README.md
@@ -98,6 +98,8 @@ The author of the Silk icon set is Mark James.
     
       Non-slicing actions (no G-code will be generated):
         --repair            Repair given STL files and save them as <name>_fixed.obj
+        --cut <z>           Cut given input files at given Z (relative) and export
+                            them as <name>_upper.stl and <name>_lower.stl
         --info              Output information about the supplied file(s) and exit
     
         -j, --threads <num> Number of threads to use (1+, default: 2)
diff --git a/lib/Slic3r/Format/STL.pm b/lib/Slic3r/Format/STL.pm
index d53a61ad..c21f9b85 100644
--- a/lib/Slic3r/Format/STL.pm
+++ b/lib/Slic3r/Format/STL.pm
@@ -25,13 +25,15 @@ sub read_file {
 
 sub write_file {
     my $self = shift;
-    my ($file, $model, %params) = @_;
+    my ($file, $mesh, %params) = @_;
+    
+    $mesh = $mesh->mesh if $mesh->isa('Slic3r::Model');
     
     my $path = Slic3r::encode_path($file);
     
     $params{binary}
-        ? $model->mesh->write_binary($path)
-        : $model->mesh->write_ascii($path);
+        ? $mesh->write_binary($path)
+        : $mesh->write_ascii($path);
 }
 
 1;
diff --git a/lib/Slic3r/Model.pm b/lib/Slic3r/Model.pm
index a39fd165..b80bc5ed 100644
--- a/lib/Slic3r/Model.pm
+++ b/lib/Slic3r/Model.pm
@@ -191,6 +191,21 @@ sub has_objects_with_no_instances {
     return (first { !defined $_->instances } @{$self->objects}) ? 1 : 0;
 }
 
+# makes sure all objects have at least one instance
+sub add_default_instances {
+    my ($self) = @_;
+    
+    # apply a default position to all objects not having one
+    my $added = 0;
+    foreach my $object (@{$self->objects}) {
+        if (!defined $object->instances) {
+            $object->add_instance(offset => [0,0]);
+            $added = 1;
+        }
+    }
+    return $added;
+}
+
 # this returns the bounding box of the *transformed* instances
 sub bounding_box {
     my $self = shift;
diff --git a/lib/Slic3r/Print/Simple.pm b/lib/Slic3r/Print/Simple.pm
index 8fa9889f..794661d8 100644
--- a/lib/Slic3r/Print/Simple.pm
+++ b/lib/Slic3r/Print/Simple.pm
@@ -46,13 +46,8 @@ sub set_model {
     # make method idempotent so that the object is reusable
     $self->_print->delete_all_objects;
     
-    my $need_arrange = $model->has_objects_with_no_instances;
-    if ($need_arrange) {
-        # apply a default position to all objects not having one
-        foreach my $object (@{$model->objects}) {
-            $object->add_instance(offset => [0,0]) if !defined $object->instances;
-        }
-    }
+    # make sure all objects have at least one defined instance
+    my $need_arrange = $model->add_default_instances;
     
     # apply scaling and rotation supplied from command line if any
     foreach my $instance (map @{$_->instances}, @{$model->objects}) {
diff --git a/slic3r.pl b/slic3r.pl
index f9e6f637..73b6c373 100755
--- a/slic3r.pl
+++ b/slic3r.pl
@@ -36,6 +36,7 @@ my %cli_options = ();
         'export-svg'            => \$opt{export_svg},
         'merge|m'               => \$opt{merge},
         'repair'                => \$opt{repair},
+        'cut=f'                 => \$opt{cut},
         'info'                  => \$opt{info},
         
         'scale=f'               => \$opt{scale},
@@ -120,6 +121,25 @@ if (@ARGV) {  # slicing from command line
         exit;
     }
     
+    if ($opt{cut}) {
+        foreach my $file (@ARGV) {
+            my $model = Slic3r::Model->read_from_file($file);
+            $model->add_default_instances;
+            my $mesh = $model->mesh;
+            $mesh->translate(0, 0, -$mesh->bounding_box->z_min);
+            my $upper = Slic3r::TriangleMesh->new;
+            my $lower = Slic3r::TriangleMesh->new;
+            $mesh->cut($opt{cut}, $upper, $lower);
+            $upper->repair;
+            $lower->repair;
+            Slic3r::Format::STL->write_file("${file}_upper.stl", $upper, binary => 0)
+                if $upper->facets_count > 0;
+            Slic3r::Format::STL->write_file("${file}_lower.stl", $lower, binary => 0)
+                if $lower->facets_count > 0;
+        }
+        exit;
+    }
+    
     while (my $input_file = shift @ARGV) {
         my $model;
         if ($opt{merge}) {
@@ -203,6 +223,8 @@ Usage: slic3r.pl [ OPTIONS ] [ file.stl ] [ file2.stl ] ...
   
   Non-slicing actions (no G-code will be generated):
     --repair            Repair given STL files and save them as <name>_fixed.obj
+    --cut <z>           Cut given input files at given Z (relative) and export
+                        them as <name>_upper.stl and <name>_lower.stl
     --info              Output information about the supplied file(s) and exit
     
 $j
diff --git a/xs/src/TriangleMesh.cpp b/xs/src/TriangleMesh.cpp
index 005ffd0d..5b2332c6 100644
--- a/xs/src/TriangleMesh.cpp
+++ b/xs/src/TriangleMesh.cpp
@@ -755,7 +755,7 @@ TriangleMeshSlicer::make_expolygons(std::vector<IntersectionLine> &lines, ExPoly
 void
 TriangleMeshSlicer::cut(float z, TriangleMesh* upper, TriangleMesh* lower)
 {
-    std::vector<IntersectionLine> lines;
+    std::vector<IntersectionLine> upper_lines, lower_lines;
     
     float scaled_z = scale_(z);
     for (int facet_idx = 0; facet_idx < this->mesh->stl.stats.number_of_facets; facet_idx++) {
@@ -766,13 +766,26 @@ TriangleMeshSlicer::cut(float z, TriangleMesh* upper, TriangleMesh* lower)
         float max_z = fmaxf(facet->vertex[0].z, fmaxf(facet->vertex[1].z, facet->vertex[2].z));
         
         // intersect facet with cutting plane
+        std::vector<IntersectionLine> lines;
         this->slice_facet(scaled_z, *facet, facet_idx, min_z, max_z, &lines);
         
+        // save intersection lines for generating correct triangulations
+        for (std::vector<IntersectionLine>::iterator it = lines.begin(); it != lines.end(); ++it) {
+            if (it->edge_type == feTop) {
+                lower_lines.push_back(*it);
+            } else if (it->edge_type == feBottom) {
+                upper_lines.push_back(*it);
+            } else if (it->edge_type != feHorizontal) {
+                lower_lines.push_back(*it);
+                upper_lines.push_back(*it);
+            }
+        }
+        
         if (min_z > z || (min_z == z && max_z > min_z)) {
-            // facet is above the cut plane but does not belong to it
+            // facet is above the cut plane and does not belong to it
             if (upper != NULL) stl_add_facet(&upper->stl, facet);
         } else if (max_z < z || (max_z == z && max_z > min_z)) {
-            // facet is below the cut plane but does not belong to it
+            // facet is below the cut plane and does not belong to it
             if (lower != NULL) stl_add_facet(&lower->stl, facet);
         } else if (min_z < z && max_z > z) {
             // facet is cut by the slicing plane
@@ -803,18 +816,21 @@ TriangleMeshSlicer::cut(float z, TriangleMesh* upper, TriangleMesh* lower)
             
             // build the triangular facet
             stl_facet triangle;
+            triangle.normal = facet->normal;
             triangle.vertex[0] = *v0;
             triangle.vertex[1] = v0v1;
             triangle.vertex[2] = v2v0;
             
             // build the facets forming a quadrilateral on the other side
             stl_facet quadrilateral[2];
+            quadrilateral[0].normal = facet->normal;
             quadrilateral[0].vertex[0] = *v1;
             quadrilateral[0].vertex[1] = *v2;
             quadrilateral[0].vertex[2] = v0v1;
+            quadrilateral[1].normal = facet->normal;
             quadrilateral[1].vertex[0] = *v2;
-            quadrilateral[1].vertex[0] = v2v0;
-            quadrilateral[1].vertex[0] = v0v1;
+            quadrilateral[1].vertex[1] = v2v0;
+            quadrilateral[1].vertex[2] = v0v1;
             
             if (v0->z > z) {
                 if (upper != NULL) stl_add_facet(&upper->stl, &triangle);
@@ -832,9 +848,53 @@ TriangleMeshSlicer::cut(float z, TriangleMesh* upper, TriangleMesh* lower)
         }
     }
     
-    // compute shape of section
-    ExPolygons section;
-    this->make_expolygons(lines, &section);
+    // triangulate holes of upper mesh
+    if (upper != NULL) {
+        // compute shape of section
+        ExPolygons section;
+        this->make_expolygons(upper_lines, &section);
+        
+        // triangulate section
+        Polygons triangles;
+        for (ExPolygons::const_iterator expolygon = section.begin(); expolygon != section.end(); ++expolygon)
+            expolygon->triangulate(&triangles);
+        
+        // convert triangles to facets and append them to mesh
+        for (Polygons::const_iterator polygon = triangles.begin(); polygon != triangles.end(); ++polygon) {
+            Polygon p = *polygon;
+            p.reverse();
+            stl_facet facet;
+            for (size_t i = 0; i <= 2; ++i) {
+                facet.vertex[i].x = unscale(p.points[i].x);
+                facet.vertex[i].y = unscale(p.points[i].y);
+                facet.vertex[i].z = z;
+            }
+            //stl_add_facet(&upper->stl, &facet);
+        }
+    }
+    
+    // triangulate holes of lower mesh
+    if (lower != NULL) {
+        // compute shape of section
+        ExPolygons section;
+        this->make_expolygons(lower_lines, &section);
+        
+        // triangulate section
+        Polygons triangles;
+        for (ExPolygons::const_iterator expolygon = section.begin(); expolygon != section.end(); ++expolygon)
+            expolygon->triangulate(&triangles);
+        
+        // convert triangles to facets and append them to mesh
+        for (Polygons::const_iterator polygon = triangles.begin(); polygon != triangles.end(); ++polygon) {
+            stl_facet facet;
+            for (size_t i = 0; i <= 2; ++i) {
+                facet.vertex[i].x = unscale(polygon->points[i].x);
+                facet.vertex[i].y = unscale(polygon->points[i].y);
+                facet.vertex[i].z = z;
+            }
+            //stl_add_facet(&lower->stl, &facet);
+        }
+    }
     
     /*
     stl_get_size(&(upper->stl));
diff --git a/xs/t/01_trianglemesh.t b/xs/t/01_trianglemesh.t
index 9b1f2175..5c18de5a 100644
--- a/xs/t/01_trianglemesh.t
+++ b/xs/t/01_trianglemesh.t
@@ -108,7 +108,7 @@ my $cube = {
         my $lower = Slic3r::TriangleMesh->new;
         $m->cut(0, $upper, $lower);
         #$upper->repair; $lower->repair;
-        is $upper->facets_count, 10, 'upper mesh has all facets except those belonging to the slicing plane';
+        is $upper->facets_count, 12, 'upper mesh has all facets except those belonging to the slicing plane';
         is $lower->facets_count,  0, 'lower mesh has no facets';
     }
     {
@@ -116,8 +116,8 @@ my $cube = {
         my $lower = Slic3r::TriangleMesh->new;
         $m->cut(10, $upper, $lower);
         #$upper->repair; $lower->repair;
-        is $upper->facets_count, 14, 'upper mesh has the right number of facets';
-        is $lower->facets_count, 14, 'lower mesh has the right number of facets';
+        is $upper->facets_count, 16, 'upper mesh has the right number of facets';
+        is $lower->facets_count, 16, 'lower mesh has the right number of facets';
     }
 }