fix ordering objects by min y

#4147

src/libslic3r/GCode.cpp

@@ -1248,16 +1248,18 @@ static inline std::vector<const PrintInstance*> sort_object_instances_by_max_y(c
  instances.emplace_back(&object->instances()[i]);
  // Calculate the convex hull of a printable object. 
  Polygon poly = object->model_object()->convex_hull_2d(
- Geometry::assemble_transform(Vec3d::Zero(),
- object->instances()[i].model_instance->get_rotation(), 
- object->instances()[i].model_instance->get_scaling_factor(), 
- object->instances()[i].model_instance->get_mirror()));
- poly.translate(object->instances()[i].shift - object->center_offset());
- coord_t min_y = poly.first_point().y();
- for (const Point& point : poly.points)
- if (point.y() < min_y)
- min_y = point.y();
- map_min_y[instances.back()] = min_y;
+ object->trafo()
+ // already in object->trafo()
+ //* Geometry::assemble_transform(Vec3d::Zero(),
+ // object->instances()[i].model_instance->get_rotation(), 
+ // object->instances()[i].model_instance->get_scaling_factor(), 
+ // object->instances()[i].model_instance->get_mirror())
+ );
+ BoundingBox bb(poly.points);
+ Vec2crd offset = object->instances()[i].shift - object->center_offset();
+ bb.translate(offset.x(), offset.y());
+ std::cout<<"bbobj (mod*inst) "<<i<<" : x:"<<unscaled(bb.min.x())<<"->"<<unscaled(bb.max.x())<<" ; y:"<<unscaled(bb.min.y())<<"->"<<unscaled(bb.max.y())<<"\n";
+ map_min_y[instances.back()] = bb.min.y();
  }
  }
  std::sort(instances.begin(), instances.end(), [&map_min_y](const PrintInstance* po1, const PrintInstance* po2) { return map_min_y[po1] < map_min_y[po2]; });