diff --git a/lib/Slic3r/GCode.pm b/lib/Slic3r/GCode.pm
index 752ead5c..53e87155 100644
--- a/lib/Slic3r/GCode.pm
+++ b/lib/Slic3r/GCode.pm
@@ -14,6 +14,8 @@ has 'enable_loop_clipping' => (is => 'rw', default => sub {1});
 has 'enable_wipe'        => (is => 'lazy');   # at least one extruder has wipe enabled
 has 'layer_count'        => (is => 'ro', required => 1 );
 has 'layer'              => (is => 'rw');
+has '_layer_islands'     => (is => 'rw');
+has '_upper_layer_islands'  => (is => 'rw');
 has '_layer_overhangs'   => (is => 'rw');
 has 'move_z_callback'    => (is => 'rw');
 has 'shift_x'            => (is => 'rw', default => sub {0} );
@@ -98,7 +100,14 @@ sub change_layer {
     
     $self->layer($layer);
     
-    # avoid computing overhangs if they're not needed
+    # avoid computing islands and overhangs if they're not needed
+    if ($self->config->only_retract_when_crossing_perimeters) {
+        $self->_layer_islands([ $layer->islands ]);
+        $self->_upper_layer_islands([ $layer->upper_layer_islands ]);
+    } else {
+        $self->_layer_islands([]);
+        $self->_upper_layer_islands([]);
+    }
     $self->_layer_overhangs(
         $layer->id > 0 && ($Slic3r::Config->overhangs || $Slic3r::Config->start_perimeters_at_non_overhang)
             ? [ map $_->expolygon, grep $_->surface_type == S_TYPE_BOTTOM, map @{$_->slices}, @{$layer->regions} ]
@@ -374,9 +383,9 @@ sub travel_to {
     # *and* in an island in the upper layer (so that the ooze will not be visible)
     if ($travel->length < scale $self->extruder->retract_before_travel
         || ($self->config->only_retract_when_crossing_perimeters
-            && (first { $_->encloses_line($travel, scaled_epsilon) } @{$self->layer->upper_layer_slices})
-            && (first { $_->encloses_line($travel, scaled_epsilon) } @{$self->layer->slices}))
-        || ($role == EXTR_ROLE_SUPPORTMATERIAL && $self->layer->support_islands_enclose_line($travel))
+            && (first { $_->encloses_line($travel, scaled_epsilon) } @{$self->_upper_layer_islands})
+            && (first { $_->encloses_line($travel, scaled_epsilon) } @{$self->_layer_islands}))
+        || ($role == EXTR_ROLE_SUPPORTMATERIAL && (first { $_->encloses_line($travel, scaled_epsilon) } @{$self->layer->support_islands}))
         ) {
         $self->straight_once(0);
         $self->speed('travel');
diff --git a/lib/Slic3r/Layer.pm b/lib/Slic3r/Layer.pm
index d1bc2818..a1b56b91 100644
--- a/lib/Slic3r/Layer.pm
+++ b/lib/Slic3r/Layer.pm
@@ -23,11 +23,16 @@ sub _trigger_id {
     $_->_trigger_layer for @{$self->regions || []};
 }
 
-sub upper_layer_slices {
+sub islands {
+    my $self = shift;
+    return @{$self->slices};
+}
+
+sub upper_layer_islands {
     my $self = shift;
     
-    my $upper_layer = $self->object->layers->[ $self->id + 1 ] or return [];
-    return $upper_layer->slices;
+    my $upper_layer = $self->object->layers->[ $self->id + 1 ] or return ();
+    return $upper_layer->islands;
 }
 
 sub region {
@@ -56,20 +61,18 @@ sub make_perimeters {
     $_->make_perimeters for @{$self->regions};
 }
 
-sub support_islands_enclose_line {
-    my $self = shift;
-    my ($line) = @_;
-    return 0 if !$self->support_islands;   # why can we arrive here if there are no support islands?
-    return (first { $_->encloses_line($line) } @{$self->support_islands}) ? 1 : 0;
-}
-
 package Slic3r::Layer::Support;
 use Moo;
 extends 'Slic3r::Layer';
 
 # ordered collection of extrusion paths to fill surfaces for support material
-has 'support_islands'           => (is => 'rw');
+has 'support_islands'           => (is => 'rw', default => sub { [] });
 has 'support_fills'             => (is => 'rw');
 has 'support_interface_fills'   => (is => 'rw');
 
+sub islands {
+    my $self = shift;
+    return @{$self->slices}, @{$self->support_islands};
+}
+
 1;
diff --git a/lib/Slic3r/Print.pm b/lib/Slic3r/Print.pm
index 1ca8ef38..ac75f542 100644
--- a/lib/Slic3r/Print.pm
+++ b/lib/Slic3r/Print.pm
@@ -682,7 +682,7 @@ sub make_brim {
         # -0.5 because islands are not represented by their centerlines
         # (first offset more, then step back - reverse order than the one used for 
         # perimeters because here we're offsetting outwards)
-        push @loops, offset2(\@islands, ($i + 1.0) * $flow->scaled_spacing, -1.5 * $flow->scaled_spacing, undef, JT_SQUARE);
+        push @loops, offset2(\@islands, ($i + 0.5) * $flow->scaled_spacing, -1.0 * $flow->scaled_spacing, undef, JT_SQUARE);
     }
     
     @{$self->brim} = map Slic3r::ExtrusionLoop->pack(
diff --git a/lib/Slic3r/Print/Object.pm b/lib/Slic3r/Print/Object.pm
index 6ad17771..524716f4 100644
--- a/lib/Slic3r/Print/Object.pm
+++ b/lib/Slic3r/Print/Object.pm
@@ -1192,6 +1192,7 @@ sub generate_support_material {
         my $support_collection = Slic3r::ExtrusionPath::Collection->new(paths => $result->{support});
         $layer->support_fills($support_collection) if @{$support_collection->paths} > 0;
         
+        # TODO: use a Slic3r::ExPolygon::Collection
         $layer->support_islands($result->{islands});
     };
     Slic3r::parallelize(