New high_res_perimeters option (like the "Skin" plugin for Skeinforge)

README.markdown

@@ -40,6 +40,7 @@ Slic3r current features are:
 * retraction;
 * skirt (with rounded corners);
 * use relative or absolute extrusion commands;
+* high-res perimeters (like the "Skin" plugin for Skeinforge);
 * center print around bed center point;
 * multiple solid layers near horizontal external surfaces;
 * ability to scale, rotate and multiply input object;

lib/Slic3r.pm

@@ -45,9 +45,10 @@ our $perimeter_feed_rate        = 30;   # mm/sec
 our $bottom_layer_speed_ratio   = 0.3;
 
 # accuracy options
-our $resolution         = 0.00000001;
-our $layer_height       = 0.4;
-our $thickness_ratio    = 1;
+our $resolution             = 0.00000001;
+our $layer_height           = 0.4;
+our $high_res_perimeters    = 0;
+our $thickness_ratio        = 1;
 our $flow_width;
 
 # print options

lib/Slic3r/Config.pm

@@ -59,6 +59,10 @@ our $Options = {
         label   => 'Layer height (mm)',
         type    => 'f',
     },
+    'high_res_perimeters' => {
+        label   => 'High-res perimeters',
+        type    => 'bool',
+    },
     
     # print options
     'perimeter_offsets' => {

lib/Slic3r/Extruder.pm

@@ -4,6 +4,7 @@ use Moo;
 has 'shift_x'            => (is => 'ro', default => sub {0} );
 has 'shift_y'            => (is => 'ro', default => sub {0} );
 has 'z'                  => (is => 'rw', default => sub {0} );
+has 'flow_ratio'         => (is => 'rw', default => sub {1});
 
 has 'extrusion_distance' => (is => 'rw', default => sub {0} );
 has 'retracted'          => (is => 'rw', default => sub {1} );  # this spits out some plastic at start
@@ -90,6 +91,7 @@ sub extrude {
         my $e = $line->a->distance_to($line->b) * $Slic3r::resolution
             * (($Slic3r::nozzle_diameter**2) / ($Slic3r::filament_diameter ** 2))
             * $Slic3r::thickness_ratio 
+            * $self->flow_ratio
             * $Slic3r::filament_packing_density;
         
         $gcode .= $self->G1($line->b, undef, $e, $description);

lib/Slic3r/GUI/SkeinPanel.pm

@@ -29,7 +29,7 @@ sub new {
         ),
         accuracy => Slic3r::GUI::OptionsGroup->new($self,
             title => 'Accuracy',
-            options => [qw(layer_height)],
+            options => [qw(layer_height high_res_perimeters)],
         ),
         print => Slic3r::GUI::OptionsGroup->new($self,
             title => 'Print settings',

lib/Slic3r/Print.pm

@@ -211,6 +211,18 @@ sub export_gcode {
     # write gcode commands layer by layer
     foreach my $layer (@{ $self->layers }) {
         
+        # with the --high-res-perimeters options enabled we extrude perimeters for
+        # each layer twice at half height
+        if ($Slic3r::high_res_perimeters && $layer->id > 0) {
+            # go to half-layer
+            printf $fh $extruder->move_z($Slic3r::z_offset + $layer->z * $Slic3r::resolution - $Slic3r::layer_height/2);
+            
+            # extrude perimeters
+            $extruder->flow_ratio(0.5);
+            printf $fh $extruder->extrude_loop($_, 'perimeter') for @{ $layer->perimeters };
+            $extruder->flow_ratio(1);
+        }
+        
         # go to layer
         printf $fh $extruder->move_z($Slic3r::z_offset + $layer->z * $Slic3r::resolution);
         

slic3r.pl

@@ -40,6 +40,7 @@ GetOptions(
     
     # accuracy options
     'layer-height=f'        => \$Slic3r::layer_height,
+    'high-res-perimeters'   => \$Slic3r::high_res_perimeters,
     
     # print options
     'perimeters=i'          => \$Slic3r::perimeter_offsets,
@@ -139,6 +140,9 @@ Usage: slic3r.pl [ OPTIONS ] file.stl
     
   Accuracy options:
     --layer-height      Layer height in mm (default: $Slic3r::layer_height)
+    --high-res-perimeters
+                        Print perimeters at half layer height to get surface accuracy
+                        (default: disabled)
   
   Print options:
     --perimeters        Number of perimeters/horizontal skins (range: 1+,