diff --git a/lib/Slic3r/Extruder.pm b/lib/Slic3r/Extruder.pm
index dee04177..42fe15a6 100644
--- a/lib/Slic3r/Extruder.pm
+++ b/lib/Slic3r/Extruder.pm
@@ -70,6 +70,9 @@ sub extrude {
     my $self = shift;
     my ($path, $description, $recursive) = @_;
     
+    $path->merge_continuous_lines;
+    
+    # detect arcs
     if ($Slic3r::gcode_arcs && !$recursive) {
         my $gcode = "";
         $gcode .= $self->extrude($_, $description, 1) for $path->detect_arcs;
@@ -173,8 +176,8 @@ sub G2_G3 {
     
     # XY distance of the center from the start position
     $gcode .= sprintf " I%.${dec}f J%.${dec}f",
-        ($point->[X] - $self->last_pos->[X]) * $Slic3r::resolution + $self->shift_x,
-        ($point->[Y] - $self->last_pos->[Y]) * $Slic3r::resolution + $self->shift_y;
+        ($center->[X] - $self->last_pos->[X]) * $Slic3r::resolution,
+        ($center->[Y] - $self->last_pos->[Y]) * $Slic3r::resolution;
     
     $self->last_pos($point);
     return $self->_Gx($gcode, $e, $comment);
diff --git a/lib/Slic3r/ExtrusionPath.pm b/lib/Slic3r/ExtrusionPath.pm
index 67c32807..3c33f650 100644
--- a/lib/Slic3r/ExtrusionPath.pm
+++ b/lib/Slic3r/ExtrusionPath.pm
@@ -76,9 +76,10 @@ sub split_at_acute_angles {
 
 sub detect_arcs {
     my $self = shift;
+    my ($max_angle, $len_epsilon) = @_;
     
-    my $max_angle = deg2rad(40);
-    my $len_epsilon = 1000000;
+    $max_angle = deg2rad($max_angle || 15);
+    $len_epsilon ||= 10 / $Slic3r::resolution;
     
     my @points = @{$self->points};
     my @paths = ();
@@ -111,34 +112,13 @@ sub detect_arcs {
             my $s1s2_angle = $s2_angle - $s1_angle;
             my $s2s3_angle = $s3_angle - $s2_angle;
             next if abs($s1s2_angle - $s2s3_angle) > $Slic3r::Geometry::parallel_degrees_limit;
-            next if $s1s2_angle < $Slic3r::Geometry::parallel_degrees_limit;     # ignore parallel lines
+            next if abs($s1s2_angle) < $Slic3r::Geometry::parallel_degrees_limit;     # ignore parallel lines
             next if $s1s2_angle > $max_angle;  # ignore too sharp vertices
-            
-            # s1, s2, s3 form an arc
-            my $orientation = $s1->point_on_left($points[$i+2]) ? 'ccw' : 'cw';
-            
-            # to find the center, we intersect the perpendicular lines
-            # passing by midpoints of $s1 and $s3
-            my $arc_center;
-            {
-                my $s1_mid = $s1->midpoint;
-                my $s3_mid = $s2->midpoint;
-                my $rotation_angle = PI/2 * ($orientation eq 'ccw' ? -1 : 1);
-                my $ray1 = Slic3r::Line->new($s1_mid, rotate_points($rotation_angle, $s1_mid, $points[$i+1]));
-                my $ray3 = Slic3r::Line->new($s3_mid, rotate_points($rotation_angle, $s3_mid, $points[$i+3]));
-                $arc_center = $ray1->intersection($ray3, 0);
-            }
-            
-            my $arc = Slic3r::ExtrusionPath::Arc->new(
-                points      => [$points[$i], $points[$i+3]],  # first and last points
-                orientation => $orientation,
-                center      => $arc_center,
-                radius      => $arc_center->distance_to($points[$i]),
-            );
+            my @arc_points = ($points[$i], $points[$i+3]),  # first and last points
             
             # now look for more points
             my $last_line_angle = $s3_angle;
-            my $last_j = $points[$i+3];
+            my $last_j = $i+3;
             for (my $j = $i+3; $j < $#points; $j++) {
                 my $line = Slic3r::Line->new($points[$j], $points[$j+1]);
                 last if abs($line->length - $s1_len) > $len_epsilon;
@@ -148,12 +128,38 @@ sub detect_arcs {
                 last if abs($s1s2_angle - $anglediff) > $Slic3r::Geometry::parallel_degrees_limit;
                 
                 # point $j+1 belongs to the arc
-                $arc->points->[-1] = $points[$j+1];
+                $arc_points[-1] = $points[$j+1];
                 $last_j = $j+1;
                 
                 $last_line_angle = $line_angle;
             }
             
+            # s1, s2, s3 form an arc
+            my $orientation = $s1->point_on_left($points[$i+2]) ? 'ccw' : 'cw';
+            
+            # to find the center, we intersect the perpendicular lines
+            # passing by midpoints of $s1 and last segment
+            # a better method would be to draw all the perpendicular lines
+            # and find the centroid of the enclosed polygon, or to
+            # intersect multiple lines and find the centroid of the convex hull
+            # around the intersections
+            my $arc_center;
+            {
+                my $s1_mid = $s1->midpoint;
+                my $last_mid = Slic3r::Line->new($points[$last_j-1], $points[$last_j])->midpoint;
+                my $rotation_angle = PI/2 * ($orientation eq 'ccw' ? -1 : 1);
+                my $ray1     = Slic3r::Line->new($s1_mid,   rotate_points($rotation_angle, $s1_mid,   $points[$i+1]));
+                my $last_ray = Slic3r::Line->new($last_mid, rotate_points($rotation_angle, $last_mid, $points[$last_j]));
+                $arc_center = $ray1->intersection($last_ray, 0);
+            }
+            
+            my $arc = Slic3r::ExtrusionPath::Arc->new(
+                points      => [@arc_points],
+                orientation => $orientation,
+                center      => $arc_center,
+                radius      => $arc_center->distance_to($points[$i]),
+            );
+            
             # points 0..$i form a linear path
             push @paths, (ref $self)->new(
                 points       => [ @points[0..$i] ],
@@ -162,7 +168,8 @@ sub detect_arcs {
             
             # add our arc
             push @paths, $arc;
-            print "ARC DETECTED\n";
+            Slic3r::debugf "ARC DETECTED\n";
+            
             # remove arc points from path, leaving one
             splice @points, 0, $last_j, ();
             
@@ -175,7 +182,7 @@ sub detect_arcs {
     push @paths, (ref $self)->new(
         points => [@points],
         depth_layers => $self->depth_layers
-    ) if @points;
+    ) if @points > 1;
     
     return @paths;
 }
diff --git a/lib/Slic3r/ExtrusionPath/Collection.pm b/lib/Slic3r/ExtrusionPath/Collection.pm
index 4a435861..53950c25 100644
--- a/lib/Slic3r/ExtrusionPath/Collection.pm
+++ b/lib/Slic3r/ExtrusionPath/Collection.pm
@@ -57,7 +57,7 @@ sub cleanup {
 
 sub detect_arcs {
     my $self = shift;
-    @{$self->paths} = map $_->detect_arcs, @{$self->paths};
+    @{$self->paths} = map $_->detect_arcs(@_), @{$self->paths};
 }
 
 1;
diff --git a/t/arcs.t b/t/arcs.t
index 2d604d57..e901823e 100644
--- a/t/arcs.t
+++ b/t/arcs.t
@@ -2,7 +2,7 @@ use Test::More;
 use strict;
 use warnings;
 
-plan tests => 2;
+plan tests => 6;
 
 BEGIN {
     use FindBin;
@@ -11,15 +11,46 @@ BEGIN {
 
 use Slic3r;
 
-my $path = Slic3r::ExtrusionPath->cast([
-    [135322.42,26654.96], [187029.11,99546.23], [222515.14,92381.93], [258001.16,99546.23], 
-    [286979.42,119083.91], [306517.1,148062.17], [313681.4,183548.2],
-    [306517.1,219034.23], [286979.42,248012.49], [258001.16,267550.17], [222515.14,274714.47], 
-    [187029.11,267550.17], [158050.85,248012.49], [138513.17,219034.23], [131348.87,183548.2], 
-    [86948.77,175149.09], [119825.35,100585],
-]);
-my $collection = Slic3r::ExtrusionPath::Collection->new(paths => [$path]);
-$collection->detect_arcs;
+{
+    my $path = Slic3r::ExtrusionPath->cast([
+        [135322.42,26654.96], [187029.11,99546.23], [222515.14,92381.93], [258001.16,99546.23], 
+        [286979.42,119083.91], [306517.1,148062.17], [313681.4,183548.2],
+        [306517.1,219034.23], [286979.42,248012.49], [258001.16,267550.17], [222515.14,274714.47], 
+        [187029.11,267550.17], [158050.85,248012.49], [138513.17,219034.23], [131348.87,183548.2], 
+        [86948.77,175149.09], [119825.35,100585],
+    ]);
+    
+    use Slic3r::SVG;
+    local $Slic3r::resolution = 0.0001;
+    Slic3r::SVG::output(undef, "arc.svg",
+        polylines => [ $path->points ],
+    );
+    
+    my $collection = Slic3r::ExtrusionPath::Collection->new(paths => [$path]);
+    $collection->detect_arcs(30);
+    
+    is scalar(@{$collection->paths}), 3, 'path collection now contains three paths';
+    isa_ok $collection->paths->[1], 'Slic3r::ExtrusionPath::Arc', 'second one';
+}
 
-is scalar(@{$collection->paths}), 3, 'path collection now contains three paths';
-isa_ok $collection->paths->[1], 'Slic3r::ExtrusionPath::Arc', 'second one';
+#==========================================================
+
+{
+    my $path = Slic3r::ExtrusionPath->cast([
+        [10,20], [10.7845909572784,19.9691733373313], [11.5643446504023,19.8768834059514], 
+        [12.3344536385591,19.7236992039768], [13.0901699437495,19.5105651629515], 
+        [13.8268343236509,19.2387953251129], [14.5399049973955,18.9100652418837], 
+        [15.2249856471595,18.5264016435409], [15.8778525229247,18.0901699437495], 
+        [16.4944804833018,17.6040596560003],
+    ]);
+    my $collection = Slic3r::ExtrusionPath::Collection->new(paths => [$path]);
+    $collection->detect_arcs(10, 1);
+    
+    is scalar(@{$collection->paths}), 1, 'path collection now contains one path';
+    isa_ok $collection->paths->[0], 'Slic3r::ExtrusionPath::Arc', 'path';
+    is $collection->paths->[0]->orientation, 'cw', 'orientation was correctly detected';
+    my $center = [ map sprintf('%.0f', $_), @{ $collection->paths->[0]->center } ];
+    is_deeply $center, [10,10], 'center was correctly detected';
+}
+
+#==========================================================