diff --git a/xs/src/libslic3r/Layer.hpp b/xs/src/libslic3r/Layer.hpp
index 02cb196553..6339434c74 100644
--- a/xs/src/libslic3r/Layer.hpp
+++ b/xs/src/libslic3r/Layer.hpp
@@ -22,7 +22,8 @@ class LayerRegion
     friend class Layer;
 
     public:
-    Layer* layer();
+    Layer* layer() { return this->_layer; }
+    const Layer* layer() const { return this->_layer; }
     PrintRegion* region() { return this->_region; }
     const PrintRegion* region() const { return this->_region; }
 
@@ -76,8 +77,8 @@ class LayerRegion
     Layer *_layer;
     PrintRegion *_region;
 
-    LayerRegion(Layer *layer, PrintRegion *region);
-    ~LayerRegion();
+    LayerRegion(Layer *layer, PrintRegion *region) : _layer(layer), _region(region) {}
+    ~LayerRegion() {}
 };
 
 
diff --git a/xs/src/libslic3r/LayerRegion.cpp b/xs/src/libslic3r/LayerRegion.cpp
index 211a882714..dc2783f9ad 100644
--- a/xs/src/libslic3r/LayerRegion.cpp
+++ b/xs/src/libslic3r/LayerRegion.cpp
@@ -14,22 +14,6 @@
 
 namespace Slic3r {
 
-LayerRegion::LayerRegion(Layer *layer, PrintRegion *region)
-:   _layer(layer),
-    _region(region)
-{
-}
-
-LayerRegion::~LayerRegion()
-{
-}
-
-Layer*
-LayerRegion::layer()
-{
-    return this->_layer;
-}
-
 Flow
 LayerRegion::flow(FlowRole role, bool bridge, double width) const
 {
@@ -134,26 +118,26 @@ LayerRegion::process_external_surfaces(const Layer* lower_layer)
         // bottom_polygons are used to trim inflated top surfaces.
         fill_boundaries.reserve(number_polygons(surfaces));
         bool has_infill = this->region()->config.fill_density.value > 0.;
-        for (Surfaces::iterator surface = this->fill_surfaces.surfaces.begin(); surface != this->fill_surfaces.surfaces.end(); ++surface) {
-            if (surface->surface_type == stTop) {
+        for (const Surface &surface : this->fill_surfaces.surfaces) {
+            if (surface.surface_type == stTop) {
                 // Collect the top surfaces, inflate them and trim them by the bottom surfaces.
                 // This gives the priority to bottom surfaces.
-                surfaces_append(top, offset_ex(surface->expolygon, float(margin), EXTERNAL_SURFACES_OFFSET_PARAMETERS), *surface);
-            } else if (surface->surface_type == stBottom || (surface->surface_type == stBottomBridge && lower_layer == NULL)) {
+                surfaces_append(top, offset_ex(surface.expolygon, float(margin), EXTERNAL_SURFACES_OFFSET_PARAMETERS), surface);
+            } else if (surface.surface_type == stBottom || (surface.surface_type == stBottomBridge && lower_layer == NULL)) {
                 // Grown by 3mm.
-                surfaces_append(bottom, offset_ex(surface->expolygon, float(margin), EXTERNAL_SURFACES_OFFSET_PARAMETERS), *surface);
-            } else if (surface->surface_type == stBottomBridge) {
-                if (! surface->empty())
-                    bridges.push_back(*surface);
+                surfaces_append(bottom, offset_ex(surface.expolygon, float(margin), EXTERNAL_SURFACES_OFFSET_PARAMETERS), surface);
+            } else if (surface.surface_type == stBottomBridge) {
+                if (! surface.empty())
+                    bridges.push_back(surface);
             }
-            bool internal_surface = surface->surface_type != stTop && ! surface->is_bottom();
-            if (has_infill || surface->surface_type != stInternal) {
+            bool internal_surface = surface.surface_type != stTop && ! surface.is_bottom();
+            if (has_infill || surface.surface_type != stInternal) {
                 if (internal_surface)
                     // Make a copy as the following line uses the move semantics.
-                    internal.push_back(*surface);
-                polygons_append(fill_boundaries, STDMOVE(surface->expolygon));
+                    internal.push_back(surface);
+                polygons_append(fill_boundaries, STDMOVE(surface.expolygon));
             } else if (internal_surface)
-                internal.push_back(STDMOVE(*surface));
+                internal.push_back(STDMOVE(surface));
         }
     }
 
diff --git a/xs/src/libslic3r/PrintObject.cpp b/xs/src/libslic3r/PrintObject.cpp
index 039911c716..d5c60cfedb 100644
--- a/xs/src/libslic3r/PrintObject.cpp
+++ b/xs/src/libslic3r/PrintObject.cpp
@@ -526,15 +526,19 @@ PrintObject::process_external_surfaces()
     BOOST_LOG_TRIVIAL(info) << "Processing external surfaces...";
 
     FOREACH_REGION(this->_print, region) {
-        size_t region_id = region - this->_print->regions.begin();
+        int region_id = int(region - this->_print->regions.begin());
         
-        FOREACH_LAYER(this, layer_it) {
-            const Layer* lower_layer = (layer_it == this->layers.begin())
-                ? NULL
-                : *(layer_it-1);
-            BOOST_LOG_TRIVIAL(trace) << "Processing external surface, layer" << (*layer_it)->print_z;
-            (*layer_it)->get_region(region_id)->process_external_surfaces(lower_layer);
-        }
+        BOOST_LOG_TRIVIAL(debug) << "Processing external surfaces for region " << region_id << " in parallel - start";
+        tbb::parallel_for(
+            tbb::blocked_range<size_t>(0, this->layers.size()),
+            [this, region_id](const tbb::blocked_range<size_t>& range) {
+                for (size_t layer_idx = range.begin(); layer_idx < range.end(); ++ layer_idx) {
+                    // BOOST_LOG_TRIVIAL(trace) << "Processing external surface, layer" << this->layers[layer_idx]->print_z;
+                    this->layers[layer_idx]->get_region(region_id)->process_external_surfaces((layer_idx == 0) ? NULL : this->layers[layer_idx - 1]);
+                }
+            }
+        );
+        BOOST_LOG_TRIVIAL(debug) << "Processing external surfaces for region " << region_id << " in parallel - end";
     }
 }