Add back m_nominal_z to store main print_z as GcodeWriter::m_pos will…

… be changed after parsing get_last_z_from_gcode

src/libslic3r/GCode.cpp

@@ -4521,6 +4521,7 @@ std::string GCode::change_layer(coordf_t print_z)
 
  m_need_change_layer_lift_z = true;
 
+ m_nominal_z = z;
  m_writer.get_position().z() = z;
 
  // forget last wiping path as wiping after raising Z is pointless
@@ -5095,7 +5096,7 @@ std::string GCode::_extrude(const ExtrusionPath &path, std::string description,
 
  const auto get_sloped_z = [&sloped, this](double z_ratio) {
  const auto height = sloped->height;
- return lerp(m_writer.get_position().z() - height, m_writer.get_position().z(), z_ratio);
+ return lerp(m_nominal_z - height, m_nominal_z, z_ratio);
  };
 
  // go to first point of extrusion path
@@ -6011,7 +6012,7 @@ std::string GCode::travel_to(const Point& point, ExtrusionRole role, std::string
  if (travel.size() == 2) {
  // No extra movements emitted by avoid_crossing_perimeters, simply move to the end point with z change
  const auto& dest2d = this->point_to_gcode(travel.points.back());
- Vec3d dest3d(dest2d(0), dest2d(1), z == DBL_MAX ? m_writer.get_position().z() : z);
+ Vec3d dest3d(dest2d(0), dest2d(1), z == DBL_MAX ? m_nominal_z : z);
  gcode += m_writer.travel_to_xyz(dest3d, comment, m_need_change_layer_lift_z);
  m_need_change_layer_lift_z = false;
  } else {
@@ -6021,7 +6022,7 @@ std::string GCode::travel_to(const Point& point, ExtrusionRole role, std::string
  if (i == 1) {
  // Lift to normal z at beginning
  Vec2d dest2d = this->point_to_gcode(travel.points[i]);
- Vec3d dest3d(dest2d(0), dest2d(1), m_writer.get_position().z());
+ Vec3d dest3d(dest2d(0), dest2d(1), m_nominal_z);
  gcode += m_writer.travel_to_xyz(dest3d, comment, m_need_change_layer_lift_z);
  m_need_change_layer_lift_z = false;
  } else if (z != DBL_MAX && i == travel.size() - 1) {

src/libslic3r/GCode.hpp

@@ -184,7 +184,8 @@ class GCode {
  m_silent_time_estimator_enabled(false),
  m_last_obj_copy(nullptr, Point(std::numeric_limits<coord_t>::max(), std::numeric_limits<coord_t>::max())),
  // BBS
- m_toolchange_count(0)
+ m_toolchange_count(0),
+ m_nominal_z(0.)
  {}
  ~GCode() = default;
 
@@ -590,6 +591,7 @@ class GCode {
  // BBS
  Print* m_curr_print = nullptr;
  unsigned int m_toolchange_count;
+ coordf_t m_nominal_z;
  bool m_need_change_layer_lift_z = false;
  int m_start_gcode_filament = -1;