diff --git a/lib/Slic3r/GUI/3DScene.pm b/lib/Slic3r/GUI/3DScene.pm
index c00484fde6..c05de06c67 100644
--- a/lib/Slic3r/GUI/3DScene.pm
+++ b/lib/Slic3r/GUI/3DScene.pm
@@ -1316,12 +1316,18 @@ sub Render {
             $self->mark_volumes_for_layer_height;
             $self->volumes->set_print_box($self->bed_bounding_box->x_min, $self->bed_bounding_box->y_min, 0.0, $self->bed_bounding_box->x_max, $self->bed_bounding_box->y_max, $self->{config}->get('max_print_height'));
             $self->volumes->update_outside_state($self->{config}, 0);
+            # do not cull backfaces to show broken geometry, if any
+            glDisable(GL_CULL_FACE);
         }
         $self->{plain_shader}->enable if $self->{plain_shader};
         $self->volumes->render_VBOs;
         $self->{plain_shader}->disable;
+        glEnable(GL_CULL_FACE) if ($self->enable_picking);
     } else {
+        # do not cull backfaces to show broken geometry, if any
+        glDisable(GL_CULL_FACE) if ($self->enable_picking);
         $self->volumes->render_legacy;
+        glEnable(GL_CULL_FACE) if ($self->enable_picking);
     }
 
     # draw cutting plane
@@ -1358,6 +1364,9 @@ sub draw_volumes {
     # $fakecolor is a boolean indicating, that the objects shall be rendered in a color coding the object index for picking.
     my ($self, $fakecolor) = @_;
     
+    # do not cull backfaces to show broken geometry, if any
+    glDisable(GL_CULL_FACE);
+    
     glEnable(GL_BLEND);
     glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
     
@@ -1385,6 +1394,8 @@ sub draw_volumes {
     }
     glDisableClientState(GL_NORMAL_ARRAY);
     glDisable(GL_BLEND);
+
+    glEnable(GL_CULL_FACE);
     
     if (defined $self->cutting_plane_z) {
         glLineWidth(2);
@@ -1812,6 +1823,7 @@ sub _fragment_shader_Gouraud {
     return <<'FRAGMENT';
 #version 110
 
+const vec4 OUTSIDE_COLOR = vec4(0.24, 0.42, 0.62, 1.0);
 const vec3 ZERO = vec3(0.0, 0.0, 0.0);
 
 // x = tainted, y = specular;
@@ -1824,13 +1836,11 @@ uniform vec4 uniform_color;
 
 void main()
 {
-    gl_FragColor = vec4(intensity.y, intensity.y, intensity.y, 0.0) + uniform_color * intensity.x;
+    // if the fragment is outside the print volume use predefined color
+    vec4 color = (any(lessThan(delta_box_min, ZERO)) || any(greaterThan(delta_box_max, ZERO))) ? OUTSIDE_COLOR : uniform_color;
 
-    // if the fragment is outside the print volume darken it and set it as transparent
-    if (any(lessThan(delta_box_min, ZERO)) || any(greaterThan(delta_box_max, ZERO)))
-        gl_FragColor = vec4(mix(gl_FragColor.xyz, ZERO, 0.5), 0.5 * uniform_color.a);
-    else
-        gl_FragColor.a = uniform_color.a;
+    gl_FragColor = vec4(intensity.y, intensity.y, intensity.y, 0.0) + color * intensity.x;
+    gl_FragColor.a = color.a;
 }
 
 FRAGMENT
diff --git a/lib/Slic3r/GUI/Plater.pm b/lib/Slic3r/GUI/Plater.pm
index 1b26857e92..0138d3f39e 100644
--- a/lib/Slic3r/GUI/Plater.pm
+++ b/lib/Slic3r/GUI/Plater.pm
@@ -98,6 +98,16 @@ sub new {
         $self->update;
     };
     
+    # callback to enable/disable action buttons
+    my $enable_action_buttons = sub {
+        my ($enable) = @_;
+        $self->{btn_export_gcode}->Enable($enable);
+        $self->{btn_reslice}->Enable($enable);
+        $self->{btn_print}->Enable($enable);
+        $self->{btn_send_gcode}->Enable($enable);
+        $self->{btn_export_stl}->Enable($enable);    
+    };
+    
     # Initialize 3D plater
     if ($Slic3r::GUI::have_OpenGL) {
         $self->{canvas3D} = Slic3r::GUI::Plater::3D->new($self->{preview_notebook}, $self->{objects}, $self->{model}, $self->{print}, $self->{config});
@@ -113,6 +123,7 @@ sub new {
         $self->{canvas3D}->set_on_decrease_objects(sub { $self->decrease() });
         $self->{canvas3D}->set_on_remove_object(sub { $self->remove() });
         $self->{canvas3D}->set_on_instances_moved($on_instances_moved);
+        $self->{canvas3D}->set_on_enable_action_buttons($enable_action_buttons);
         $self->{canvas3D}->use_plain_shader(1);
         $self->{canvas3D}->set_on_wipe_tower_moved(sub {
             my ($new_pos_3f) = @_;
diff --git a/lib/Slic3r/GUI/Plater/3D.pm b/lib/Slic3r/GUI/Plater/3D.pm
index 37e1321aec..09cc029302 100644
--- a/lib/Slic3r/GUI/Plater/3D.pm
+++ b/lib/Slic3r/GUI/Plater/3D.pm
@@ -12,7 +12,7 @@ use Wx::Locale gettext => 'L';
 
 __PACKAGE__->mk_accessors(qw(
     on_arrange on_rotate_object_left on_rotate_object_right on_scale_object_uniformly
-    on_remove_object on_increase_objects on_decrease_objects));
+    on_remove_object on_increase_objects on_decrease_objects on_enable_action_buttons));
 
 sub new {
     my $class = shift;
@@ -176,6 +176,11 @@ sub set_on_model_update {
     $self->on_model_update($cb);
 }
 
+sub set_on_enable_action_buttons {
+    my ($self, $cb) = @_;
+    $self->on_enable_action_buttons($cb);
+}
+
 sub reload_scene {
     my ($self, $force) = @_;
 
@@ -217,10 +222,12 @@ sub reload_scene {
         if (!$self->{model}->fits_print_volume($self->{config})) {
             $self->set_warning_enabled(1);
             Slic3r::GUI::_3DScene::generate_warning_texture(L("Detected object outside print volume"));
+            $self->on_enable_action_buttons->(0) if ($self->on_enable_action_buttons);
         } else {
             $self->set_warning_enabled(0);
             $self->volumes->update_outside_state($self->{config}, 1);
             Slic3r::GUI::_3DScene::reset_warning_texture();
+            $self->on_enable_action_buttons->(1) if ($self->on_enable_action_buttons);
         }
     }
 }
diff --git a/xs/src/libslic3r/Model.cpp b/xs/src/libslic3r/Model.cpp
index 6f1ce1ce5c..ad2ce54cd2 100644
--- a/xs/src/libslic3r/Model.cpp
+++ b/xs/src/libslic3r/Model.cpp
@@ -450,6 +450,8 @@ bool Model::fits_print_volume(const DynamicPrintConfig* config) const
 
     BoundingBox bed_box_2D = get_extents(Polygon::new_scale(opt->values));
     BoundingBoxf3 print_volume(Pointf3(unscale(bed_box_2D.min.x), unscale(bed_box_2D.min.y), 0.0), Pointf3(unscale(bed_box_2D.max.x), unscale(bed_box_2D.max.y), config->opt_float("max_print_height")));
+    // Allow the objects to protrude below the print bed
+    print_volume.min.z = -1e10;
     return print_volume.contains(transformed_bounding_box());
 }
 
@@ -459,6 +461,8 @@ bool Model::fits_print_volume(const FullPrintConfig &config) const
         return true;
     BoundingBox bed_box_2D = get_extents(Polygon::new_scale(config.bed_shape.values));
     BoundingBoxf3 print_volume(Pointf3(unscale(bed_box_2D.min.x), unscale(bed_box_2D.min.y), 0.0), Pointf3(unscale(bed_box_2D.max.x), unscale(bed_box_2D.max.y), config.max_print_height));
+    // Allow the objects to protrude below the print bed
+    print_volume.min.z = -1e10;
     return print_volume.contains(transformed_bounding_box());
 }
 
diff --git a/xs/src/slic3r/GUI/3DScene.cpp b/xs/src/slic3r/GUI/3DScene.cpp
index 0db81d99bb..a459b7cbf5 100644
--- a/xs/src/slic3r/GUI/3DScene.cpp
+++ b/xs/src/slic3r/GUI/3DScene.cpp
@@ -194,8 +194,8 @@ void GLIndexedVertexArray::render(
 
 const float GLVolume::SELECTED_COLOR[4] = { 0.0f, 1.0f, 0.0f, 1.0f };
 const float GLVolume::HOVER_COLOR[4] = { 0.4f, 0.9f, 0.1f, 1.0f };
-const float GLVolume::OUTSIDE_COLOR[4] = { 0.75f, 0.0f, 0.75f, 1.0f };
-const float GLVolume::SELECTED_OUTSIDE_COLOR[4] = { 1.0f, 0.0f, 1.0f, 1.0f };
+const float GLVolume::OUTSIDE_COLOR[4] = { 0.0f, 0.38f, 0.8f, 1.0f };
+const float GLVolume::SELECTED_OUTSIDE_COLOR[4] = { 0.19f, 0.58f, 1.0f, 1.0f };
 
 void GLVolume::set_render_color(float r, float g, float b, float a)
 {
@@ -627,6 +627,8 @@ void GLVolumeCollection::update_outside_state(const DynamicPrintConfig* config,
 
     BoundingBox bed_box_2D = get_extents(Polygon::new_scale(opt->values));
     BoundingBoxf3 print_volume(Pointf3(unscale(bed_box_2D.min.x), unscale(bed_box_2D.min.y), 0.0), Pointf3(unscale(bed_box_2D.max.x), unscale(bed_box_2D.max.y), config->opt_float("max_print_height")));
+    // Allow the objects to protrude below the print bed
+    print_volume.min.z = -1e10;
 
     for (GLVolume* volume : this->volumes)
     {