diff --git a/README.markdown b/README.markdown
index 094ece767..236c4fcd5 100644
--- a/README.markdown
+++ b/README.markdown
@@ -49,14 +49,14 @@ Roadmap includes the following goals:
 * support material for internal perimeters;
 * new and better GUI;
 * cool;
-* other fill patterns.
+* more fill patterns.
 
 ## Is it usable already? Any known limitation?
 
 Sure, it's very usable. Remember that:
 
 * it doesn't generate support material;
-* it only works well with manifold models (check them with Meshlab or Netfabb or http://cloud.netfabb.com/).
+* it only works well with manifold and clean models (check them with Meshlab or Netfabb or http://cloud.netfabb.com/).
 
 ## How to install?
 
diff --git a/lib/Slic3r/ExtrusionLoop.pm b/lib/Slic3r/ExtrusionLoop.pm
index caee31ede..ed91651b4 100644
--- a/lib/Slic3r/ExtrusionLoop.pm
+++ b/lib/Slic3r/ExtrusionLoop.pm
@@ -26,7 +26,7 @@ sub split_at {
     
     # find index of point
     my $i = -1;
-    for (my $n = 0; $n <= $#{$self->polygon}; $n++) {ZZZ "here" if ref $self->polygon->[$n] eq 'ARRAY'; 
+    for (my $n = 0; $n <= $#{$self->polygon}; $n++) {
         if ($point->id eq $self->polygon->[$n]->id) {
             $i = $n;
             last;
diff --git a/lib/Slic3r/Fill.pm b/lib/Slic3r/Fill.pm
index eab0633dd..98aa2a6ef 100644
--- a/lib/Slic3r/Fill.pm
+++ b/lib/Slic3r/Fill.pm
@@ -161,6 +161,17 @@ sub make_fill {
             ],
         ) if @paths;
     }
+    
+    # add thin fill regions
+    push @{ $layer->fills }, Slic3r::ExtrusionPath::Collection->new(
+        paths => [
+            map {
+                $_->isa('Slic3r::Polygon')
+                    ? Slic3r::ExtrusionLoop->new(polygon => $_, role => 'solid-fill')->split_at($_->[0])
+                    : Slic3r::ExtrusionPath->new(polyline => $_, role => 'solid-fill')
+            } @{$layer->thin_fills},
+        ],
+    ) if @{$layer->thin_fills};
 }
 
 1;
diff --git a/lib/Slic3r/Layer.pm b/lib/Slic3r/Layer.pm
index 4f2701105..5d36d0591 100644
--- a/lib/Slic3r/Layer.pm
+++ b/lib/Slic3r/Layer.pm
@@ -34,6 +34,10 @@ has 'thin_walls' => (is => 'ro', default => sub { [] });
 # they represent boundaries of areas to fill
 has 'fill_boundaries' => (is => 'ro', default => sub { [] });
 
+# collection of polygons or polylines representing thin infill regions that
+# need to be filled with a medial axis
+has 'thin_fills' => (is => 'ro', default => sub { [] });
+
 # collection of surfaces generated by clipping the slices to the fill boundaries
 has 'surfaces' => (
     is      => 'rw',
diff --git a/lib/Slic3r/Perimeter.pm b/lib/Slic3r/Perimeter.pm
index ed9f7df0a..2b64f83a8 100644
--- a/lib/Slic3r/Perimeter.pm
+++ b/lib/Slic3r/Perimeter.pm
@@ -3,6 +3,7 @@ use Moo;
 
 use Math::Clipper ':all';
 use Slic3r::Geometry qw(X Y shortest_path scale);
+use Slic3r::Geometry::Clipper qw(diff_ex);
 use XXX;
 
 sub make_perimeter {
@@ -42,6 +43,7 @@ sub make_perimeter {
         for (my $loop = 0; $loop < $Slic3r::perimeters; $loop++) {
             # offsetting a polygon can result in one or many offset polygons
             @last_offsets = map $_->offset_ex(-$distance), @last_offsets if $distance;
+            last if !@last_offsets;
             push @{ $perimeters[-1] }, [@last_offsets];
             
             # offset distance for inner loops
@@ -51,12 +53,18 @@ sub make_perimeter {
         # create one more offset to be used as boundary for fill
         {
             my @fill_boundaries = map $_->offset_ex(-$distance), @last_offsets;
+            push @{ $layer->fill_boundaries }, @fill_boundaries;
             
-            # TODO: diff(offset(@last_offsets, -$distance/2), offset(@fill_boundaries, +$distance/2))
-            # this represents the small gaps that we need to treat like thin polygons,
+            # detect the small gaps that we need to treat like thin polygons,
             # thus generating the skeleton and using it to fill them
-            
-            push @{ $layer->fill_boundaries }, @fill_boundaries if @fill_boundaries;
+            my $small_gaps = diff_ex(
+                [ map @$_, map $_->offset_ex(-$distance/2), map @$_, @{$perimeters[-1]} ],
+                [ map @$_, map $_->offset_ex(+$distance/2), @fill_boundaries ],
+            );
+            push @{ $layer->thin_fills },
+                grep $_,
+                map $_->medial_axis(scale $Slic3r::flow_width),
+                @$small_gaps;
         }
     }
     
diff --git a/lib/Slic3r/Point.pm b/lib/Slic3r/Point.pm
index f8d3af071..5d471e3b3 100644
--- a/lib/Slic3r/Point.pm
+++ b/lib/Slic3r/Point.pm
@@ -12,8 +12,6 @@ sub new {
     } elsif ($_[0]->isa(__PACKAGE__)) {
         return $_[0];
     } else {
-        use XXX;
-        ZZZ \@_;
         die "Invalid arguments for ${class}->new";
     }
     bless $self, $class;
diff --git a/lib/Slic3r/Surface.pm b/lib/Slic3r/Surface.pm
index 8605f7b81..1b7b37888 100644
--- a/lib/Slic3r/Surface.pm
+++ b/lib/Slic3r/Surface.pm
@@ -61,7 +61,7 @@ sub clipper_polygon {
 }
 
 sub p {
-    my $self = shift;use XXX; ZZZ $self->expolygon if !eval { 1 if @{$self->expolygon}; 1 };
+    my $self = shift;
     return @{$self->expolygon};
 }