diff --git a/lib/Slic3r/Format/AMF/Parser.pm b/lib/Slic3r/Format/AMF/Parser.pm
index 19fc60e65..24732dbc8 100644
--- a/lib/Slic3r/Format/AMF/Parser.pm
+++ b/lib/Slic3r/Format/AMF/Parser.pm
@@ -20,6 +20,7 @@ sub start_element {
     
     if ($data->{LocalName} eq 'object') {
         $self->{_object} = $self->{_model}->add_object;
+        $self->{_object_vertices} = [];
         $self->{_objects_map}{ $self->_get_attribute($data, 'id') } = $#{ $self->{_model}->objects };
     } elsif ($data->{LocalName} eq 'vertex') {
         $self->{_vertex} = ["", "", ""];
@@ -28,7 +29,9 @@ sub start_element {
     } elsif ($data->{LocalName} eq 'volume') {
         $self->{_volume} = $self->{_object}->add_volume(
             material_id => $self->_get_attribute($data, 'materialid') // undef,
+            mesh        => Slic3r::TriangleMesh->new,
         );
+        $self->{_volume_facets} = [];
     } elsif ($data->{LocalName} eq 'triangle') {
         $self->{_triangle} = ["", "", ""];
     } elsif ($self->{_triangle} && $data->{LocalName} =~ /^v([123])$/ && $self->{_tree}[-1] eq 'triangle') {
@@ -75,15 +78,19 @@ sub end_element {
     
     if ($data->{LocalName} eq 'object') {
         $self->{_object} = undef;
+        $self->{_object_vertices} = undef;
     } elsif ($data->{LocalName} eq 'vertex') {
-        push @{$self->{_object}->vertices}, $self->{_vertex};
+        push @{$self->{_object_vertices}}, $self->{_vertex};
         $self->{_vertex} = undef;
     } elsif ($self->{_coordinate} && $data->{LocalName} =~ /^[xyz]$/) {
         $self->{_coordinate} = undef;
     } elsif ($data->{LocalName} eq 'volume') {
+        $self->{_volume}->mesh->ReadFromPerl($self->{_object_vertices}, $self->{_volume_facets});
+        $self->{_volume}->mesh->repair;
         $self->{_volume} = undef;
+        $self->{_volume_facets} = undef;
     } elsif ($data->{LocalName} eq 'triangle') {
-        push @{$self->{_volume}->facets}, $self->{_triangle};
+        push @{$self->{_volume_facets}}, $self->{_triangle};
         $self->{_triangle} = undef;
     } elsif (defined $self->{_vertex_idx} && $data->{LocalName} =~ /^v[123]$/) {
         $self->{_vertex_idx} = undef;
@@ -113,7 +120,7 @@ sub end_document {
         foreach my $instance (@{ $self->{_instances}{$object_id} }) {
             $self->{_model}->objects->[$new_object_id]->add_instance(
                 rotation => $instance->{rz} || 0,
-                offset   => [ $instance->{deltax} || 0, $instance->{deltay} || 0 ],
+                offset   => Slic3r::Point->new($instance->{deltax} || 0, $instance->{deltay} || 0),
             );
         }
     }
diff --git a/lib/Slic3r/Format/OBJ.pm b/lib/Slic3r/Format/OBJ.pm
index 05a141db1..621fe24dc 100644
--- a/lib/Slic3r/Format/OBJ.pm
+++ b/lib/Slic3r/Format/OBJ.pm
@@ -17,9 +17,13 @@ sub read_file {
     }
     close $fh;
     
+    my $mesh = Slic3r::TriangleMesh->new;
+    $mesh->ReadFromPerl($vertices, $facets);
+    $mesh->repair;
+    
     my $model = Slic3r::Model->new;
-    my $object = $model->add_object(vertices => $vertices);
-    my $volume = $object->add_volume(facets => $facets);
+    my $object = $model->add_object;
+    my $volume = $object->add_volume(mesh => $mesh);
     return $model;
 }
 
diff --git a/lib/Slic3r/Model.pm b/lib/Slic3r/Model.pm
index 2be84e227..d7c8f235e 100644
--- a/lib/Slic3r/Model.pm
+++ b/lib/Slic3r/Model.pm
@@ -25,7 +25,9 @@ sub merge {
     my $class = shift;
     my @models = @_;
     
-    my $new_model = $class->new;
+    my $new_model = ref($class)
+        ? $class
+        : $class->new;
     foreach my $model (@models) {
         # merge material attributes (should we rename them in case of duplicates?)
         $new_model->set_material($_, { %{$model->materials->{$_}}, %{$model->materials->{$_} || {}} })
@@ -34,14 +36,13 @@ sub merge {
         foreach my $object (@{$model->objects}) {
             my $new_object = $new_model->add_object(
                 input_file          => $object->input_file,
-                vertices            => $object->vertices,
                 config              => $object->config,
                 layer_height_ranges => $object->layer_height_ranges,
             );
             
             $new_object->add_volume(
                 material_id         => $_->material_id,
-                facets              => $_->facets,
+                mesh                => $_->mesh->clone,
             ) for @{$object->volumes};
             
             $new_object->add_instance(
@@ -431,6 +432,13 @@ sub needed_repair {
     return (first { !$_->mesh->needed_repair } @{$self->volumes}) ? 0 : 1;
 }
 
+sub mesh_stats {
+    my $self = shift;
+    
+    # TODO: sum values from all volumes
+    return $self->volumes->[0]->mesh->stats;
+}
+
 sub print_info {
     my $self = shift;