Fix an issue that wrong z value was used if a new layer is started wi…

…th wipe tower extrusions. (#6980)

…

# Description

This update, along with #6934, resolves the remaining issues with the
wipe tower.

The GCode class will no longer maintain its own Z height information
(m_nominal_z). Instead, it will utilize the Z height from GCodeWriter's
m_pos. This approach is less error-prone.

This PR also fixes #6755.
It also enforce "Enable Filament ramming" option


@igiannakas It should fix the wipe tower crashing issue
# Screenshots/Recordings/Graphs

<!--
> Please attach relevant screenshots to showcase the UI changes.
> Please attach images that can help explain the changes.
-->

## Tests

<!--
> Please describe the tests that you have conducted to verify the
changes made in this PR.
-->

src/libslic3r/GCode.cpp

@@ -729,6 +729,8 @@ static std::vector<Vec2d> get_path_of_change_filament(const Print& print)
         gcode += gcodegen.writer().unlift(); // Make sure there is no z-hop (in most cases, there isn't).
 
         double current_z = gcodegen.writer().get_position().z();
+
+
         if (z == -1.) // in case no specific z was provided, print at current_z pos
             z = current_z;
 
@@ -741,7 +743,7 @@ static std::vector<Vec2d> get_path_of_change_filament(const Print& print)
                                                              || !needs_toolchange // this is just finishing the tower with no toolchange
                                                              || is_ramming);
 
-        if (should_travel_to_tower) {
+        if (should_travel_to_tower || gcodegen.m_need_change_layer_lift_z) {
             // FIXME: It would be better if the wipe tower set the force_travel flag for all toolchanges,
             // then we could simplify the condition and make it more readable.
             gcode += gcodegen.retract();
@@ -767,10 +769,10 @@ static std::vector<Vec2d> get_path_of_change_filament(const Print& print)
             toolchange_gcode_str = gcodegen.set_extruder(new_extruder_id, tcr.print_z); // TODO: toolchange_z vs print_z
             if (gcodegen.config().enable_prime_tower) {
             deretraction_str += gcodegen.writer().travel_to_z(z, "restore layer Z");
-            Vec3d position{gcodegen.writer().get_position()};
-            position.z() = z;
-            gcodegen.writer().set_position(position);
-            deretraction_str += gcodegen.unretract();
+                Vec3d position{gcodegen.writer().get_position()};
+                position.z() = z;
+                gcodegen.writer().set_position(position);
+                deretraction_str += gcodegen.unretract();
             }
         }
 
@@ -4516,12 +4518,11 @@ std::string GCode::change_layer(coordf_t print_z)
         comment << "move to next layer (" << m_layer_index << ")";
         gcode += m_writer.travel_to_z(z, comment.str());
     }
-    else {
-        //BBS: set m_need_change_layer_lift_z to be true so that z lift can be done in travel_to() function
-        m_need_change_layer_lift_z = true;
-    }
+
+    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
     // BBS. Dont forget wiping path to reduce stringing.
@@ -6005,14 +6006,15 @@ std::string GCode::travel_to(const Point& point, ExtrusionRole role, std::string
         if (m_spiral_vase) {
             // No lazy z lift for spiral vase mode
             for (size_t i = 1; i < travel.size(); ++i) {
-                gcode += m_writer.travel_to_xy(this->point_to_gcode(travel.points[i]), comment + " travel_to_xy");
+                gcode += m_writer.travel_to_xy(this->point_to_gcode(travel.points[i]), comment);
             }
         } else {
             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_nominal_z : z);
-                gcode += m_writer.travel_to_xyz(dest3d, comment + " travel_to_xyz");
+                gcode += m_writer.travel_to_xyz(dest3d, comment, m_need_change_layer_lift_z);
+                m_need_change_layer_lift_z = false;
             } else {
                 // Extra movements emitted by avoid_crossing_perimeters, lift the z to normal height at the beginning, then apply the z
                 // ratio at the last point
@@ -6021,21 +6023,23 @@ std::string GCode::travel_to(const Point& point, ExtrusionRole role, std::string
                         // Lift to normal z at beginning
                         Vec2d dest2d = this->point_to_gcode(travel.points[i]);
                         Vec3d dest3d(dest2d(0), dest2d(1), m_nominal_z);
-                        gcode += m_writer.travel_to_xyz(dest3d, comment + " travel_to_xyz");
+                        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) {
                         // Apply z_ratio for the very last point
                         Vec2d dest2d = this->point_to_gcode(travel.points[i]);
                         Vec3d dest3d(dest2d(0), dest2d(1), z);
-                        gcode += m_writer.travel_to_xyz(dest3d, comment + " travel_to_xyz");
+                        gcode += m_writer.travel_to_xyz(dest3d, comment);
                     } else {
                         // For all points in between, no z change
-                        gcode += m_writer.travel_to_xy(this->point_to_gcode(travel.points[i]), comment + " travel_to_xy");
+                        gcode += m_writer.travel_to_xy(this->point_to_gcode(travel.points[i]), comment);
                     }
                 }
             }
         }
         this->set_last_pos(travel.points.back());
     }
+
     return gcode;
 }
 

src/libslic3r/GCode/WipeTower2.cpp

@@ -1127,7 +1127,7 @@ void WipeTower2::toolchange_Load(
 	WipeTowerWriter2 &writer,
 	const WipeTower::box_coordinates  &cleaning_box)
 {
-    if (m_semm && (m_parking_pos_retraction != 0 || m_extra_loading_move != 0)) {
+    if (m_semm && m_enable_filament_ramming && (m_parking_pos_retraction != 0 || m_extra_loading_move != 0)) {
         float xl = cleaning_box.ld.x() + m_perimeter_width * 0.75f;
         float xr = cleaning_box.rd.x() - m_perimeter_width * 0.75f;
         float oldx = writer.x();	// the nozzle is in place to do the first wiping moves, we will remember the position

src/libslic3r/GCodeWriter.cpp

@@ -440,7 +440,7 @@ std::string GCodeWriter::travel_to_xy(const Vec2d &point, const std::string &com
     return w.string();
 }
 
-std::string GCodeWriter::travel_to_xyz(const Vec3d &point, const std::string &comment)
+std::string GCodeWriter::travel_to_xyz(const Vec3d &point, const std::string &comment, bool force_z)
 {
     // FIXME: This function was not being used when travel_speed_z was separated (bd6badf).
     // Calculation of feedrate was not updated accordingly. If you want to use
@@ -526,7 +526,7 @@ std::string GCodeWriter::travel_to_xyz(const Vec3d &point, const std::string &co
         this->set_current_position_clear(true);
         return slop_move + xy_z_move;
     }
-    else if (!this->will_move_z(point(2))) {
+    else if (!force_z && !this->will_move_z(point(2))) {
         double nominal_z = m_pos(2) - m_lifted;
         m_lifted -= (point(2) - nominal_z);
         // In case that z_hop == layer_height we could end up with almost zero in_m_lifted

src/libslic3r/GCodeWriter.hpp

@@ -69,7 +69,7 @@ class GCodeWriter {
     // SoftFever NOTE: the returned speed is mm/minute
     double      get_current_speed() const { return m_current_speed;}
     std::string travel_to_xy(const Vec2d &point, const std::string &comment = std::string());
-    std::string travel_to_xyz(const Vec3d &point, const std::string &comment = std::string());
+    std::string travel_to_xyz(const Vec3d &point, const std::string &comment = std::string(), bool force_z = false);
     std::string travel_to_z(double z, const std::string &comment = std::string());
     bool        will_move_z(double z) const;
     std::string extrude_to_xy(const Vec2d &point, double dE, const std::string &comment = std::string(), bool force_no_extrusion = false);
@@ -81,7 +81,8 @@ class GCodeWriter {
     std::string unretract();
     std::string lift(LiftType lift_type = LiftType::NormalLift, bool spiral_vase = false);
     std::string unlift();
-    Vec3d       get_position() const { return m_pos; }
+    const Vec3d& get_position() const { return m_pos; }
+    Vec3d&       get_position() { return m_pos; }
     void        set_position(const Vec3d& in) { m_pos = in; }
     double      get_zhop() const { return m_lifted; }