New option for rotating the lower part resulting from the cut so that the flat surface lies on the print bed

lib/Slic3r/GUI/Plater/ObjectCutDialog.pm

@@ -3,6 +3,7 @@ use strict;
 use warnings;
 use utf8;
 
+use Slic3r::Geometry qw(PI);
 use Wx qw(:dialog :id :misc :sizer wxTAB_TRAVERSAL);
 use Wx::Event qw(EVT_CLOSE EVT_BUTTON);
 use base 'Wx::Dialog';
@@ -20,6 +21,7 @@ sub new {
         z               => 0,
         keep_upper      => 1,
         keep_lower      => 1,
+        rotate_lower    => 1,
     };
     my $cut_button_sizer = Wx::BoxSizer->new(wxVERTICAL);
     {
@@ -48,6 +50,13 @@ sub new {
                 label       => 'Lower part',
                 default     => $self->{cut_options}{keep_lower},
             },
+            {
+                opt_key     => 'rotate_lower',
+                type        => 'bool',
+                label       => '',
+                tooltip     => 'If enabled, the lower part will be rotated by 180° so that the flat cut surface lies on the print bed.',
+                default     => $self->{cut_options}{rotate_lower},
+            },
         ],
         lines => [
             {
@@ -58,6 +67,10 @@ sub new {
                 label       => 'Keep',
                 options     => [qw(keep_upper keep_lower)],
             },
+            {
+                label       => 'Rotate lower part',
+                options     => [qw(rotate_lower)],
+            },
             {
                 sizer => $cut_button_sizer,
             },
@@ -73,7 +86,7 @@ sub new {
                 }
             }
         },
-        label_width => 50,
+        label_width => 120,
     );
     
     # left pane with tree
@@ -112,10 +125,15 @@ sub perform_cut {
     
     my ($upper_object, $lower_object) = $self->{model_object}->cut($self->{cut_options}{z});
     $self->{new_model_objects} = [];
-    push @{$self->{new_model_objects}}, $upper_object
-        if $self->{cut_options}{keep_upper} && defined $upper_object;
-    push @{$self->{new_model_objects}}, $lower_object
-        if $self->{cut_options}{keep_lower} && defined $lower_object;
+    if ($self->{cut_options}{keep_upper} && defined $upper_object) {
+        push @{$self->{new_model_objects}}, $upper_object;
+    }
+    if ($self->{cut_options}{keep_lower} && defined $lower_object) {
+        push @{$self->{new_model_objects}}, $lower_object;
+        if ($self->{cut_options}{rotate_lower}) {
+            $lower_object->rotate_x(PI);
+        }
+    }
     
     $self->Close;
 }

lib/Slic3r/Model.pm

@@ -2,7 +2,7 @@ package Slic3r::Model;
 use Moo;
 
 use List::Util qw(first max);
-use Slic3r::Geometry qw(X Y Z MIN move_points);
+use Slic3r::Geometry qw(X Y Z move_points);
 
 has 'materials' => (is => 'ro', default => sub { {} });
 has 'objects'   => (is => 'ro', default => sub { [] });
@@ -331,7 +331,7 @@ use Moo;
 
 use File::Basename qw(basename);
 use List::Util qw(first sum);
-use Slic3r::Geometry qw(X Y Z MIN MAX);
+use Slic3r::Geometry qw(X Y Z rad2deg);
 
 has 'input_file'            => (is => 'rw');
 has 'model'                 => (is => 'ro', weak_ref => 1, required => 1);
@@ -504,6 +504,16 @@ sub translate {
     $self->_bounding_box->translate(@shift) if defined $self->_bounding_box;
 }
 
+sub rotate_x {
+    my ($self, $angle) = @_;
+    
+    # we accept angle in radians but mesh currently uses degrees
+    $angle = rad2deg($angle);
+    
+    $_->mesh->rotate_x($angle) for @{$self->volumes};
+    $self->_bounding_box(undef);
+}
+
 sub materials_count {
     my $self = shift;
     

xs/src/TriangleMesh.cpp

@@ -161,6 +161,21 @@ void TriangleMesh::translate(float x, float y, float z)
     stl_translate_relative(&(this->stl), x, y, z);
 }
 
+void TriangleMesh::rotate_x(float angle)
+{
+    stl_rotate_x(&(this->stl), angle);
+}
+
+void TriangleMesh::rotate_y(float angle)
+{
+    stl_rotate_y(&(this->stl), angle);
+}
+
+void TriangleMesh::rotate_z(float angle)
+{
+    stl_rotate_z(&(this->stl), angle);
+}
+
 void TriangleMesh::align_to_origin()
 {
     this->translate(

xs/src/TriangleMesh.hpp

@@ -29,6 +29,9 @@ class TriangleMesh
     void scale(float factor);
     void scale(std::vector<double> versor);
     void translate(float x, float y, float z);
+    void rotate_x(float angle);
+    void rotate_y(float angle);
+    void rotate_z(float angle);
     void align_to_origin();
     void rotate(double angle, Point* center);
     TriangleMeshPtrs split() const;

xs/xsp/TriangleMesh.xsp

@@ -20,6 +20,9 @@
     void scale_xyz(std::vector<double> versor)
         %code{% THIS->scale(versor); %};
     void translate(float x, float y, float z);
+    void rotate_x(float angle);
+    void rotate_y(float angle);
+    void rotate_z(float angle);
     void align_to_origin();
     void rotate(double angle, Point* center);
     TriangleMeshPtrs split();