diff --git a/lib/Slic3r/Format/AMF.pm b/lib/Slic3r/Format/AMF.pm
index 247914484..ce388ec2e 100644
--- a/lib/Slic3r/Format/AMF.pm
+++ b/lib/Slic3r/Format/AMF.pm
@@ -74,7 +74,7 @@ sub write_file {
         foreach my $facet (@{$mesh->facets}) {
             printf $fh qq{        <triangle>\n};
             printf $fh qq{          <v%d>%d</v%d>\n}, $_, $facet->[$_] + $vertices_offset{$mesh}, $_
-                for 1..3;
+                for -3..-1;
             printf $fh qq{        </triangle>\n};
         }
         printf $fh qq{      </volume>\n};
diff --git a/lib/Slic3r/Format/AMF/Parser.pm b/lib/Slic3r/Format/AMF/Parser.pm
index 48f8521b8..1d8d4dc39 100644
--- a/lib/Slic3r/Format/AMF/Parser.pm
+++ b/lib/Slic3r/Format/AMF/Parser.pm
@@ -26,9 +26,9 @@ sub start_element {
         $self->{_volume_materialid} = $self->_get_attribute($data, 'materialid') || '_';
         $self->{_volume} = [];
     } elsif ($data->{LocalName} eq 'triangle') {
-        $self->{_triangle} = [[], "", "", ""];  # empty normal
+        $self->{_triangle} = ["", "", ""];
     } elsif ($self->{_triangle} && $data->{LocalName} =~ /^v([123])$/ && $self->{_tree}[-1] eq 'triangle') {
-        $self->{_vertex_idx} = $1;
+        $self->{_vertex_idx} = $1-1;
     } elsif ($data->{LocalName} eq 'material') {
         $self->{_material_id} = $self->_get_attribute($data, 'id') || '_';
         $self->{_material} = {};
diff --git a/lib/Slic3r/Format/STL.pm b/lib/Slic3r/Format/STL.pm
index 1e30394dd..29549ff8d 100644
--- a/lib/Slic3r/Format/STL.pm
+++ b/lib/Slic3r/Format/STL.pm
@@ -43,7 +43,7 @@ sub read_file {
         my %vertices_map = ();    # given a vertex's coordinates, what's its index?
         my @vertices_facets = (); # given a vertex index, what are the indexes of its tangent facets?
         for (my $f = 0; $f <= $#$facets; $f++) {
-            for (1..3) {
+            for (-3..-1) {
                 my $point_id = join ',', @{$facets->[$f][$_]};
                 if (exists $vertices_map{$point_id}) {
                     $facets->[$f][$_] = $vertices_map{$point_id};
@@ -74,11 +74,11 @@ sub read_file {
                     CYCLE: while (@facets_indexes && @this_f) {
                         
                         # look for a facet that is connected to $this_f[-1] and whose common line contains $v
-                        my @other_vertices_indexes = grep $_ != $v, @{$facets->[$this_f[-1]]}[1..3];
+                        my @other_vertices_indexes = grep $_ != $v, @{$facets->[$this_f[-1]]}[-3..-1];
                         
                         OTHER: for my $other_f (@facets_indexes) {
                             # facet is connected if it shares one more point
-                            for (grep $_ != $v, @{$facets->[$other_f]}[1..3]) {
+                            for (grep $_ != $v, @{$facets->[$other_f]}[-3..-1]) {
                                 if ($_ ~~ @other_vertices_indexes) {
                                     #printf "facet %d is connected to $other_f (sharing vertices $v and $_)\n", $this_f[-1];
                                     
@@ -107,7 +107,7 @@ sub read_file {
                         Slic3r::debugf "  more than one vertex in the same point\n";
                         push @$vertices, $vertices->[$v];
                         for my $f (@this_f) {
-                            $facets->[$f][$_] = $#$vertices for grep $facets->[$f][$_] == $v, 1..3;
+                            $facets->[$f][$_] = $#$vertices for grep $facets->[$f][$_] == $v, -3..-1;
                         }
                     }
                 }
@@ -128,7 +128,7 @@ sub _read_ascii {
     while (my $_ = <$fh>) {
         if (!$facet) {
             /^\s*facet\s+normal\s+$point_re/ or next;
-            $facet = [ [$1, $2, $3] ];
+            $facet = [];  # ignore normal: [$1, $2, $3]
         } else {
             if (/^\s*endfacet/) {
                 push @$facets, $facet;
@@ -153,7 +153,7 @@ sub _read_binary {
     seek $fh, 80 + 4, 0;
     while (read $fh, my $_, 4*4*3+2) {
         my @v = unpack '(f<3)4';
-        push @$facets, [ [@v[0..2]], [@v[3..5]], [@v[6..8]], [@v[9..11]] ];
+        push @$facets, [ [@v[3..5]], [@v[6..8]], [@v[9..11]] ];  # ignore normal: [@v[0..2]]
     }
 }
 
diff --git a/lib/Slic3r/TriangleMesh.pm b/lib/Slic3r/TriangleMesh.pm
index b95521274..3db73f8d3 100644
--- a/lib/Slic3r/TriangleMesh.pm
+++ b/lib/Slic3r/TriangleMesh.pm
@@ -5,7 +5,7 @@ use Slic3r::Geometry qw(X Y Z A B unscale same_point);
 
 # public
 has 'vertices'      => (is => 'ro', required => 1);         # id => [$x,$y,$z]
-has 'facets'        => (is => 'ro', required => 1);         # id => [ $normal, $v1_id, $v2_id, $v3_id ]
+has 'facets'        => (is => 'ro', required => 1);         # id => [ $v1_id, $v2_id, $v3_id ]
 
 # private
 has 'edges'         => (is => 'ro', default => sub { [] }); # id => [ $v1_id, $v2_id ]
@@ -36,15 +36,15 @@ sub BUILD {
     my %table = ();  # edge_coordinates => edge_id
     
     for (my $facet_id = 0; $facet_id <= $#{$self->facets}; $facet_id++) {
-        my $facet = $self->facets->[$facet_id];
+        my $facet = $self->facets->[$facet_id];##use Devel::Size qw(total_size); printf "total_size = %d\n", total_size($facet);exit;
         $self->facets_edges->[$facet_id] = [];
         
         # reorder vertices so that the first one is the one with lowest Z
         # this is needed to get all intersection lines in a consistent order
         # (external on the right of the line)
         {
-            my @z_order = sort { $self->vertices->[$facet->[$a]][Z] <=> $self->vertices->[$facet->[$b]][Z] } 1..3;
-            @$facet[1..3] = (@$facet[$z_order[0]..3], @$facet[1..($z_order[0]-1)]);
+            my @z_order = sort { $self->vertices->[$facet->[$a]][Z] <=> $self->vertices->[$facet->[$b]][Z] } -3..-1;
+            @$facet[-3..-1] = (@$facet[$z_order[0]..-1], @$facet[-3..($z_order[0]-1)]);
         }
         
         # ignore the normal if provided
@@ -83,9 +83,9 @@ sub _facet_edges {
     
     my $facet = $self->facets->[$facet_id];
     return (
-        [ $facet->[1], $facet->[2] ],
-        [ $facet->[2], $facet->[3] ],
-        [ $facet->[3], $facet->[1] ],
+        [ $facet->[-3], $facet->[-2] ],
+        [ $facet->[-2], $facet->[-1] ],
+        [ $facet->[-1], $facet->[-3] ],
     );
 }
 
@@ -198,7 +198,7 @@ sub make_loops {
         # choice)
         # The "// ''" on the next line avoids uninitialized value errors mentioned in issue #357 but these
         # errors occur on fixed models so the root cause still needs to be found
-        if (@lines_starting_here == 2 && join('', sort map $_->[I_FACET_EDGE] // '', @lines_starting_here) eq FE_TOP.FE_BOTTOM) {
+        if (@lines_starting_here == 2 && join('', sort map $_->[I_FACET_EDGE] // '', @lines_starting_here) eq FE_TOP.FE_BOTTOM) { #/
             my @to_remove = grep $_->[I_FACET_EDGE] == FE_TOP, @lines_starting_here;
             while (!grep defined $_->[I_B_ID] && $_->[I_B_ID] == $to_remove[-1]->[I_B_ID] && $_ ne $to_remove[-1], @lines) {
                 push @to_remove, grep defined $_->[I_A_ID] && $_->[I_A_ID] == $to_remove[-1]->[I_B_ID], @lines;
@@ -359,7 +359,7 @@ sub size {
 sub slice_facet {
     my $self = shift;
     my ($print_object, $facet_id) = @_;
-    my ($normal, @vertices) = @{$self->facets->[$facet_id]};
+    my @vertices = @{$self->facets->[$facet_id]}[-3..-1];
     Slic3r::debugf "\n==> FACET %d (%f,%f,%f - %f,%f,%f - %f,%f,%f):\n",
         $facet_id, map @{$self->vertices->[$_]}, @vertices
         if $Slic3r::debug;
@@ -398,7 +398,7 @@ sub intersect_facet {
     my $self = shift;
     my ($facet_id, $z) = @_;
     
-    my @vertices_ids        = @{$self->facets->[$facet_id]}[1..3];
+    my @vertices_ids        = @{$self->facets->[$facet_id]}[-3..-1];
     my @edge_ids            = @{$self->facets_edges->[$facet_id]};
     my @edge_vertices_ids   = $self->_facet_edges($facet_id);
     
@@ -534,11 +534,11 @@ sub split_mesh {
             $self->facets->[$facet_id] = undef;
         }
         
-        my %vertices = map { $_ => 1 } map @$_[1,2,3], @facets;
+        my %vertices = map { $_ => 1 } map @$_[-3..-1], @facets;
         my @new_vertices = keys %vertices;
         my %new_vertices = map { $new_vertices[$_] => $_ } 0..$#new_vertices;
         foreach my $facet (@facets) {
-            $facet->[$_] = $new_vertices{$facet->[$_]} for 1,2,3;
+            $facet->[$_] = $new_vertices{$facet->[$_]} for -3..-1;
         }
         push @meshes, Slic3r::TriangleMesh->new(
             facets => \@facets,