diff --git a/lib/Slic3r/Geometry.pm b/lib/Slic3r/Geometry.pm
index b8a9d4091..e0d2c0d22 100644
--- a/lib/Slic3r/Geometry.pm
+++ b/lib/Slic3r/Geometry.pm
@@ -86,7 +86,7 @@ sub point_in_polygon {
     }
     
     # if point is not in polygon, let's check whether it belongs to the contour
-    if (!$side) {
+    if (!$side && 0) {
         foreach my $line (polygon_lines($polygon)) {
             # calculate the Y in line at X of the point
             if ($line->[A][X] == $line->[B][X]) {
diff --git a/lib/Slic3r/Layer.pm b/lib/Slic3r/Layer.pm
index 6c80b06a1..74a962b1c 100644
--- a/lib/Slic3r/Layer.pm
+++ b/lib/Slic3r/Layer.pm
@@ -119,6 +119,28 @@ sub make_polylines {
     die "No point should be endpoint of less or more than 2 lines!"
         if grep @$_ != 2, values %pointmap;
     
+    if (0) {
+        # defensive programming
+        for (keys %pointmap) {
+            next if @{$pointmap{$_}} == 2;
+            
+            #use Slic3r::SVG;
+            #Slic3r::SVG::output_points($main::print, "points.svg", [ map [split /,/], keys %pointmap ], [ [split /,/, $_ ] ]);
+            
+            die sprintf "No point should be endpoint of less or more than 2 lines (%d)!", scalar(@{$pointmap{$_}});
+        }
+        
+        while (my @single_line_points = grep @{$pointmap{$_}} == 1, keys %pointmap) {
+            for my $point_id (@single_line_points) {
+                foreach my $lines (values %pointmap) {
+                    next unless $pointmap{$point_id}->[0];
+                    @$lines = grep $_ ne $pointmap{$point_id}->[0], @$lines;
+                }
+                delete $pointmap{$point_id};
+            }
+        }
+    }
+    
     # make a subroutine to remove lines from pointmap
     my $remove_line = sub {
         my $line = shift;
@@ -167,6 +189,9 @@ sub make_surfaces {
     my $self = shift;
     my ($polylines) = @_;
     
+    #use Slic3r::SVG;
+    #Slic3r::SVG::output_polygons($main::print, "polylines.svg", [ map $_->p, @$polylines ]);
+    
     # count how many other polylines enclose each polyline
     # even = contour; odd = hole
     my %enclosing_polylines = ();
@@ -178,6 +203,7 @@ sub make_surfaces {
         my $point = $polyline->points->[0];
         my $ordered_id = $polyline->id;
         
+        # find polylines contaning $point, and thus $polyline
         $enclosing_polylines{$polyline} = 
             [ grep $_->id ne $ordered_id && $_->encloses_point($point), @$polylines ];
         $enclosing_polylines_count{$polyline} = scalar @{ $enclosing_polylines{$polyline} };
diff --git a/lib/Slic3r/Polyline.pm b/lib/Slic3r/Polyline.pm
index afb6d90c1..5fa131863 100644
--- a/lib/Slic3r/Polyline.pm
+++ b/lib/Slic3r/Polyline.pm
@@ -14,7 +14,7 @@ has 'points' => (
 
 sub id {
     my $self = shift;
-    return join ' - ', map $_->id, @{$self->points};
+    return join ' - ', sort map $_->id, @{$self->points};
 }
 
 sub cast {
diff --git a/lib/Slic3r/STL.pm b/lib/Slic3r/STL.pm
index b539cc937..252880102 100644
--- a/lib/Slic3r/STL.pm
+++ b/lib/Slic3r/STL.pm
@@ -94,7 +94,7 @@ sub _facet {
     Slic3r::debugf "z: min = %.0f, max = %.0f\n", $min_z, $max_z;
     
     # calculate the layer extents
-    my ($min_layer, $max_layer) = map {$_ * $Slic3r::resolution / $Slic3r::layer_height} $min_z, $max_z;
+    my ($min_layer, $max_layer) = map { sprintf '%.0f', $_ * $Slic3r::resolution / $Slic3r::layer_height } $min_z, $max_z;
     Slic3r::debugf "layers: min = %.0f, max = %.0f\n", $min_layer, $max_layer;
     
     # is the facet horizontal?
@@ -159,7 +159,7 @@ sub _facet {
             
             # check whether the two points coincide due to resolution rounding
             if ($intersection_points[0]->coincides_with($intersection_points[1])) {
-                Slic3r::debugf "Points coincide; removing\n";
+                Slic3r::debugf "Points coincide at layer %d; removing\n", $layer_id;
                 next;
             }
             
diff --git a/lib/Slic3r/SVG.pm b/lib/Slic3r/SVG.pm
index 67a4f9141..40ea5ab14 100644
--- a/lib/Slic3r/SVG.pm
+++ b/lib/Slic3r/SVG.pm
@@ -8,7 +8,7 @@ use constant X => 0;
 use constant Y => 1;
 
 sub factor {
-    return $Slic3r::resolution * 100;
+    return $Slic3r::resolution * 10;
 }
 
 sub svg {
@@ -17,6 +17,44 @@ sub svg {
     return SVG->new(width => $print->max_length * factor(), height => $print->max_length * factor());
 }
 
+sub output_points {
+    my ($print, $filename, $points, $red_points) = @_;
+    $red_points ||= [];
+    
+    my $svg = svg($print);
+    my $g = $svg->group(
+        style => {
+            'stroke-width' => 2,
+            'stroke' => 'black',
+            'fill' => 'black',
+        },
+    );
+    foreach my $point (@$points) {
+        $g->circle(
+            cx      => $point->[X] * factor(),
+            cy      => $point->[Y] * factor(),
+            r       => 2,
+        );
+    }
+    
+    my $g2 = $svg->group(
+        style => {
+            'stroke-width' => 2,
+            'stroke' => 'red',
+            'fill' => 'red',
+        },
+    );
+    foreach my $point (@$red_points) {
+        $g2->circle(
+            cx      => $point->[X] * factor(),
+            cy      => $point->[Y] * factor(),
+            r       => 3,
+        );
+    }
+    
+    write_svg($svg, $filename);
+}
+
 sub output_polygons {
     my ($print, $filename, $polygons) = @_;
     
@@ -25,6 +63,7 @@ sub output_polygons {
         style => {
             'stroke-width' => 2,
             'stroke' => 'black',
+            'fill' => 'none',
         },
     );
     foreach my $polygon (@$polygons) {