Bugfix: objects were floating in STL export after rotation and flip. #2512

lib/Slic3r/GUI/Plater.pm

@@ -659,6 +659,9 @@ sub rotate {
             $_->set_rotation(0) for @{ $model_object->instances };
         }
         $model_object->rotate(deg2rad($angle), $axis);
+        
+        # realign object to Z = 0
+        $model_object->center_around_origin;
         $self->make_thumbnail($obj_idx);
     }
     
@@ -688,6 +691,9 @@ sub flip {
     
     $model_object->flip($axis);
     $model_object->update_bounding_box;
+    
+    # realign object to Z = 0
+    $model_object->center_around_origin;
     $self->make_thumbnail($obj_idx);
         
     # update print and start background processing
@@ -725,6 +731,7 @@ sub changescale {
         my $versor = [1,1,1];
         $versor->[$axis] = $scale/100;
         $model_object->scale_xyz(Slic3r::Pointf3->new(@$versor));
+        # object was already aligned to Z = 0, so no need to realign it
         $self->make_thumbnail($obj_idx);
     } else {
         # max scale factor should be above 2540 to allow importing files exported in inches

lib/Slic3r/GUI/PreviewCanvas.pm

@@ -351,8 +351,6 @@ sub set_bed_shape {
 sub load_object {
     my ($self, $object, $all_instances) = @_;
     
-    my $z_min = $object->raw_bounding_box->z_min;
-    
     # color mesh(es) by material
     my @materials = ();
     
@@ -381,7 +379,6 @@ sub load_object {
                 instance_idx    => $instance_idx,
                 mesh            => $mesh,
                 color           => $color,
-                origin          => Slic3r::Pointf3->new(0,0,-$z_min),
             );
             push @volumes_idx, $#{$self->volumes};
         

lib/Slic3r/Model.pm

@@ -272,6 +272,7 @@ sub rotate {
     } elsif ($axis == Z) {
         $_->mesh->rotate_z($angle) for @{$self->volumes};
     }
+    $self->set_origin_translation(Slic3r::Pointf3->new(0,0,0));
     $self->invalidate_bounding_box;
 }
 
@@ -285,6 +286,7 @@ sub flip {
     } elsif ($axis == Z) {
         $_->mesh->flip_z for @{$self->volumes};
     }
+    $self->set_origin_translation(Slic3r::Pointf3->new(0,0,0));
     $self->invalidate_bounding_box;
 }
 

xs/src/libslic3r/Model.cpp

@@ -520,6 +520,9 @@ ModelObject::scale(const Pointf3 &versor)
     for (ModelVolumePtrs::const_iterator v = this->volumes.begin(); v != this->volumes.end(); ++v) {
         (*v)->mesh.scale(versor);
     }
+    
+    // reset origin translation since it doesn't make sense anymore
+    this->origin_translation = Pointf3(0,0,0);
     this->invalidate_bounding_box();
 }
 

xs/src/libslic3r/Model.hpp

@@ -97,7 +97,7 @@ class ModelObject
     
     /* This vector accumulates the total translation applied to the object by the
         center_around_origin() method. Callers might want to apply the same translation
-        to new volumes before adding them to this object in order to preset alignment
+        to new volumes before adding them to this object in order to preserve alignment
         when user expects that. */
     Pointf3 origin_translation;