diff --git a/lib/Slic3r.pm b/lib/Slic3r.pm
index a8b0a5409..2c2883574 100644
--- a/lib/Slic3r.pm
+++ b/lib/Slic3r.pm
@@ -110,6 +110,7 @@ sub parallelize {
 sub thread_cleanup {
     # prevent destruction of shared objects
     no warnings 'redefine';
+    *Slic3r::ExPolygon::Collection::DESTROY = sub {};
     *Slic3r::ExPolygon::XS::DESTROY = sub {};
     *Slic3r::Point::XS::DESTROY     = sub {};
 }
diff --git a/lib/Slic3r/ExPolygon.pm b/lib/Slic3r/ExPolygon.pm
index 19b3a90b6..8330bb7f2 100644
--- a/lib/Slic3r/ExPolygon.pm
+++ b/lib/Slic3r/ExPolygon.pm
@@ -301,47 +301,19 @@ package Slic3r::ExPolygon::XS;
 use base 'Slic3r::ExPolygon';
 
 package Slic3r::ExPolygon::Collection;
-use Moo;
 use Slic3r::Geometry qw(X1 Y1);
 
-has 'expolygons' => (is => 'ro', default => sub { [] });
-
-sub clone {
-    my $self = shift;
-    return (ref $self)->new(
-        expolygons => [ map $_->clone, @{$self->expolygons} ],
-    );
-}
-
 sub align_to_origin {
     my $self = shift;
     
-    my @bb = Slic3r::Geometry::bounding_box([ map @$_, map @$_, @{$self->expolygons} ]);
-    $_->translate(-$bb[X1], -$bb[Y1]) for @{$self->expolygons};
-    $self;
-}
-
-sub scale {
-    my $self = shift;
-    $_->scale(@_) for @{$self->expolygons};
-    $self;
-}
-
-sub rotate {
-    my $self = shift;
-    $_->rotate(@_) for @{$self->expolygons};
-    $self;
-}
-
-sub translate {
-    my $self = shift;
-    $_->translate(@_) for @{$self->expolygons};
+    my @bb = Slic3r::Geometry::bounding_box([ map @$_, map @$_, @$self ]);
+    $self->translate(-$bb[X1], -$bb[Y1]);
     $self;
 }
 
 sub size {
     my $self = shift;
-    return [ Slic3r::Geometry::size_2D([ map @$_, map @$_, @{$self->expolygons} ]) ];
+    return [ Slic3r::Geometry::size_2D([ map @$_, map @$_, @$self ]) ];
 }
 
 1;
diff --git a/lib/Slic3r/GUI/Plater.pm b/lib/Slic3r/GUI/Plater.pm
index 8f62008bc..8df97c65b 100644
--- a/lib/Slic3r/GUI/Plater.pm
+++ b/lib/Slic3r/GUI/Plater.pm
@@ -161,6 +161,7 @@ sub new {
         my ($obj_idx, $thumbnail) = @{$event->GetData};
         return if !$self->{objects}[$obj_idx];  # object was deleted before thumbnail generation completed
         $self->{objects}[$obj_idx]->thumbnail($thumbnail->clone);
+        
         $self->on_thumbnail_made($obj_idx);
     });
     
@@ -869,13 +870,12 @@ sub repaint {
     @{$parent->{object_previews}} = ();
     for my $obj_idx (0 .. $#{$parent->{objects}}) {
         my $object = $parent->{objects}[$obj_idx];
-        next unless $object->thumbnail && @{$object->thumbnail->expolygons};
+        next unless defined $object->thumbnail && @{$object->thumbnail};
         for my $instance_idx (0 .. $#{$object->instances}) {
             my $instance = $object->instances->[$instance_idx];
             
-            my $thumbnail = $object->transformed_thumbnail
-                ->clone
-                ->translate(map $parent->to_pixel($instance->[$_]) + $parent->{shift}[$_], (X,Y));
+            my $thumbnail = $object->transformed_thumbnail->clone;
+            $thumbnail->translate(map $parent->to_pixel($instance->[$_]) + $parent->{shift}[$_], (X,Y));
             
             push @{$parent->{object_previews}}, [ $obj_idx, $instance_idx, $thumbnail ];
             
@@ -887,11 +887,11 @@ sub repaint {
             } else {
                 $dc->SetBrush($parent->{objects_brush});
             }
-            $dc->DrawPolygon($parent->_y($_), 0, 0) for map $_->contour, @{ $parent->{object_previews}->[-1][2]->expolygons };
+            $dc->DrawPolygon($parent->_y($_), 0, 0) for map $_->contour, @{ $parent->{object_previews}->[-1][2] };
             
             # if sequential printing is enabled and we have more than one object
             if ($parent->{config}->complete_objects && (map @{$_->instances}, @{$parent->{objects}}) > 1) {
-            	my $convex_hull = Slic3r::Polygon->new(@{convex_hull([ map @{$_->contour}, @{$parent->{object_previews}->[-1][2]->expolygons} ])});
+            	my $convex_hull = Slic3r::Polygon->new(@{convex_hull([ map @{$_->contour}, @{$parent->{object_previews}->[-1][2]} ])});
                 my ($clearance) = @{offset([$convex_hull], $parent->{config}->extruder_clearance_radius / 2 * $parent->{scaling_factor}, 100, JT_ROUND)};
                 $dc->SetPen($parent->{clearance_pen});
                 $dc->SetBrush($parent->{transparent_brush});
@@ -902,7 +902,7 @@ sub repaint {
     
     # draw skirt
     if (@{$parent->{object_previews}} && $parent->{config}->skirts) {
-        my $convex_hull = Slic3r::Polygon->new(@{convex_hull([ map @{$_->contour}, map @{$_->[2]->expolygons}, @{$parent->{object_previews}} ])});
+        my $convex_hull = Slic3r::Polygon->new(@{convex_hull([ map @{$_->contour}, map @{$_->[2]}, @{$parent->{object_previews}} ])});
         ($convex_hull) = @{offset([$convex_hull], $parent->{config}->skirt_distance * $parent->{scaling_factor}, 100, JT_ROUND)};
         $dc->SetPen($parent->{skirt_pen});
         $dc->SetBrush($parent->{transparent_brush});
@@ -924,7 +924,7 @@ sub mouse_event {
         $parent->selection_changed(0);
         for my $preview (@{$parent->{object_previews}}) {
             my ($obj_idx, $instance_idx, $thumbnail) = @$preview;
-            if (defined first { $_->contour->encloses_point($pos) } @{$thumbnail->expolygons}) {
+            if (defined first { $_->contour->encloses_point($pos) } @$thumbnail) {
                 $parent->{selected_objects} = [ [$obj_idx, $instance_idx] ];
                 $parent->{list}->Select($obj_idx, 1);
                 $parent->selection_changed(1);
@@ -954,7 +954,7 @@ sub mouse_event {
     } elsif ($event->Moving) {
         my $cursor = wxSTANDARD_CURSOR;
         for my $preview (@{$parent->{object_previews}}) {
-            if (defined first { $_->contour->encloses_point($pos) } @{ $preview->[2]->expolygons }) {
+            if (defined first { $_->contour->encloses_point($pos) } @{ $preview->[2] }) {
                 $cursor = Wx::Cursor->new(wxCURSOR_HAND);
                 last;
             }
@@ -1158,16 +1158,14 @@ sub make_thumbnail {
     
     my $mesh = $self->model_object->mesh;  # $self->model_object is already aligned to origin
     my $thumbnail = Slic3r::ExPolygon::Collection->new(
-    	expolygons => (@{$mesh->facets} <= 5000)
-    		? $mesh->horizontal_projection
-    		: [ Slic3r::ExPolygon->new($self->convex_hull) ],
+        # only simplify expolygons larger than the threshold
+        grep @$_,
+            map { ($_->area >= 1) ? $_->simplify(0.5) : $_ }
+    	    (@{$mesh->facets} <= 5000)
+    		    ? @{$mesh->horizontal_projection}
+    		    : Slic3r::ExPolygon->new($self->convex_hull)
     );
     
-    # only simplify expolygons larger than the threshold
-    @{$thumbnail->expolygons} = grep @$_,
-        map { ($_->area >= 1) ? $_->simplify(0.5) : $_ }
-        @{$thumbnail->expolygons};
-    
     $self->thumbnail($thumbnail);  # ignored in multi-threaded environments
     $self->free_model_object;
     
@@ -1177,7 +1175,7 @@ sub make_thumbnail {
 sub _transform_thumbnail {
     my $self = shift;
     
-    return unless $self->thumbnail;
+    return unless defined $self->thumbnail;
     my $t = $self->_apply_transform($self->thumbnail);
     $t->scale($self->thumbnail_scaling_factor);
     
@@ -1199,10 +1197,10 @@ sub _apply_transform {
     
     # the order of these transformations MUST be the same everywhere, including
     # in Slic3r::Print->add_model()
-    return $entity
-        ->clone
-        ->rotate(deg2rad($self->rotate), $self->bounding_box->center_2D)
-        ->scale($self->scale);
+    my $result = $entity->clone;
+    $result->rotate(deg2rad($self->rotate), Slic3r::Point::XS->new(@{$self->bounding_box->center_2D}));
+    $result->scale($self->scale);
+    return $result;
 }
 
 sub transformed_size {
diff --git a/xs/lib/Slic3r/XS.pm b/xs/lib/Slic3r/XS.pm
index b5c809f5a..c81690e72 100644
--- a/xs/lib/Slic3r/XS.pm
+++ b/xs/lib/Slic3r/XS.pm
@@ -26,4 +26,10 @@ sub rotate {
     $self->_rotate($angle, $center);
 }
 
+package Slic3r::ExPolygon::Collection;
+use overload
+    '@{}' => sub { $_[0]->arrayref };
+
+sub clone { (ref $_[0])->_clone($_[0]) }
+
 1;
diff --git a/xs/src/ExPolygon.hpp b/xs/src/ExPolygon.hpp
index 7363a6a73..154969784 100644
--- a/xs/src/ExPolygon.hpp
+++ b/xs/src/ExPolygon.hpp
@@ -100,6 +100,33 @@ polygon2perl(Polygon& poly) {
     return sv_bless(newRV_noinc((SV*)av), gv_stashpv("Slic3r::Polygon", GV_ADD));
 }
 
+void
+perl2expolygon(SV* expoly_sv, ExPolygon& expoly)
+{
+    AV* expoly_av = (AV*)SvRV(expoly_sv);
+    const unsigned int num_polygons = av_len(expoly_av)+1;
+    expoly.holes.resize(num_polygons-1);
+    
+    SV** polygon_sv = av_fetch(expoly_av, 0, 0);
+    perl2polygon(*polygon_sv, expoly.contour);
+    for (unsigned int i = 0; i < num_polygons-1; i++) {
+        polygon_sv = av_fetch(expoly_av, i+1, 0);
+        perl2polygon(*polygon_sv, expoly.holes[i]);
+    }
+}
+
+SV*
+expolygon2perl(ExPolygon& expoly) {
+    const unsigned int num_holes = expoly.holes.size();
+    AV* av = newAV();
+    av_extend(av, num_holes);  // -1 +1
+    av_store(av, 0, polygon2perl(expoly.contour));
+    for (unsigned int i = 0; i < num_holes; i++) {
+        av_store(av, i+1, polygon2perl(expoly.holes[i]));
+    }
+    return sv_bless(newRV_noinc((SV*)av), gv_stashpv("Slic3r::ExPolygon", GV_ADD));
+}
+
 }
 
 #endif
diff --git a/xs/src/ExPolygonCollection.hpp b/xs/src/ExPolygonCollection.hpp
new file mode 100644
index 000000000..127d5178f
--- /dev/null
+++ b/xs/src/ExPolygonCollection.hpp
@@ -0,0 +1,53 @@
+#ifndef slic3r_ExPolygonCollection_hpp_
+#define slic3r_ExPolygonCollection_hpp_
+
+extern "C" {
+#include "EXTERN.h"
+#include "perl.h"
+#include "XSUB.h"
+#include "ppport.h"
+}
+
+#include "ExPolygon.hpp"
+
+namespace Slic3r {
+
+typedef std::vector<ExPolygon> ExPolygons;
+
+class ExPolygonCollection
+{
+    public:
+    ExPolygons expolygons;
+    SV* arrayref();
+    void scale(double factor);
+    void translate(double x, double y);
+    void rotate(double angle, Point* center);
+};
+
+void
+ExPolygonCollection::scale(double factor)
+{
+    for (ExPolygons::iterator it = expolygons.begin(); it != expolygons.end(); ++it) {
+        (*it).scale(factor);
+    }
+}
+
+void
+ExPolygonCollection::translate(double x, double y)
+{
+   for (ExPolygons::iterator it = expolygons.begin(); it != expolygons.end(); ++it) {
+        (*it).translate(x, y);
+    }
+}
+
+void
+ExPolygonCollection::rotate(double angle, Point* center)
+{
+    for (ExPolygons::iterator it = expolygons.begin(); it != expolygons.end(); ++it) {
+        (*it)._rotate(angle, center);
+    }
+}
+
+}
+
+#endif
diff --git a/xs/t/04_expolygon.t b/xs/t/04_expolygon.t
index 0f2116c1f..a09df27b8 100644
--- a/xs/t/04_expolygon.t
+++ b/xs/t/04_expolygon.t
@@ -4,7 +4,7 @@ use strict;
 use warnings;
 
 use Slic3r::XS;
-use Test::More tests => 9;
+use Test::More tests => 11;
 
 use constant PI => 4 * atan2(1, 1);
 
@@ -71,4 +71,15 @@ isa_ok $expolygon->[0][0], 'Slic3r::Point', 'Perl polygon points are blessed';
         ], 'rotate around pure-Perl Point';
 }
 
+{
+    my $expolygon2 = $expolygon->clone;
+    $expolygon2->scale(2);
+    my $collection = Slic3r::ExPolygon::Collection->new($expolygon->arrayref, $expolygon2->arrayref);
+    is_deeply [ @$collection ], [ $expolygon->arrayref, $expolygon2->arrayref ],
+        'expolygon collection';
+    my $collection2 = Slic3r::ExPolygon::Collection->new($expolygon, $expolygon2);
+    is_deeply [ @$collection ], [ @$collection2 ],
+        'expolygon collection with XS expolygons';
+}
+
 __END__
diff --git a/xs/xsp/ExPolygon.xsp b/xs/xsp/ExPolygon.xsp
index 081b7ed25..fe7237008 100644
--- a/xs/xsp/ExPolygon.xsp
+++ b/xs/xsp/ExPolygon.xsp
@@ -8,6 +8,8 @@
 %name{Slic3r::ExPolygon::XS} class ExPolygon {
     %name{_clone} ExPolygon(ExPolygon& self);
     ~ExPolygon();
+    SV* arrayref()
+        %code{% RETVAL = expolygon2perl(*THIS); %};
     void scale(double factor);
     void translate(double x, double y);
     void _rotate(double angle, Point* center);
@@ -26,20 +28,6 @@ ExPolygon::new(...)
     OUTPUT:
         RETVAL
 
-SV*
-ExPolygon::arrayref()
-    CODE:
-        AV* av = newAV();
-        av_fill(av, THIS->holes.size());  // -1 +1
-        av_store(av, 0, polygon2perl(THIS->contour));
-        int i = 0;
-        for (Polygons::iterator it = THIS->holes.begin(); it != THIS->holes.end(); ++it) {
-            av_store(av, ++i, polygon2perl(*it));
-        }
-        RETVAL = sv_bless(newRV_noinc((SV*)av), gv_stashpv("Slic3r::ExPolygon", GV_ADD));
-    OUTPUT:
-        RETVAL
-
 %}
 };
 
diff --git a/xs/xsp/ExPolygonCollection.xsp b/xs/xsp/ExPolygonCollection.xsp
new file mode 100644
index 000000000..8696f301e
--- /dev/null
+++ b/xs/xsp/ExPolygonCollection.xsp
@@ -0,0 +1,48 @@
+%module{Slic3r::XS};
+
+%{
+#include <myinit.h>
+#include "ExPolygonCollection.hpp"
+%}
+
+%name{Slic3r::ExPolygon::Collection} class ExPolygonCollection {
+    %name{_clone} ExPolygonCollection(ExPolygonCollection& self);
+    ~ExPolygonCollection();
+    void scale(double factor);
+    void translate(double x, double y);
+    void rotate(double angle, Point* center);
+%{
+
+ExPolygonCollection*
+ExPolygonCollection::new(...)
+    CODE:
+        RETVAL = new ExPolygonCollection ();
+        // ST(0) is class name, others are expolygons
+        RETVAL->expolygons.resize(items-1);
+        for (unsigned int i = 1; i < items; i++) {
+            if (sv_isobject(ST(i)) && (SvTYPE(SvRV(ST(i))) == SVt_PVMG)) {
+                // a XS ExPolygon was supplied
+                RETVAL->expolygons[i-1] = *(ExPolygon *)SvIV((SV*)SvRV( ST(i) ));
+            } else {
+                // a Perl arrayref was supplied
+                perl2expolygon(ST(i), RETVAL->expolygons[i-1]);
+            }
+        }
+    OUTPUT:
+        RETVAL
+
+SV*
+ExPolygonCollection::arrayref()
+    CODE:
+        AV* av = newAV();
+        av_fill(av, THIS->expolygons.size()-1);
+        int i = 0;
+        for (ExPolygons::iterator it = THIS->expolygons.begin(); it != THIS->expolygons.end(); ++it) {
+            av_store(av, i++, expolygon2perl(*it));
+        }
+        RETVAL = newRV_noinc((SV*)av);
+    OUTPUT:
+        RETVAL
+
+%}
+};
diff --git a/xs/xsp/my.map b/xs/xsp/my.map
index 7c189907b..9737c8c05 100644
--- a/xs/xsp/my.map
+++ b/xs/xsp/my.map
@@ -2,3 +2,4 @@ ZTable*         O_OBJECT
 TriangleMesh*         O_OBJECT
 Point*         O_OBJECT
 ExPolygon*      O_OBJECT
+ExPolygonCollection*    O_OBJECT