diff --git a/src/libslic3r/ExtrusionEntity.cpp b/src/libslic3r/ExtrusionEntity.cpp
index 65182c3d9..3fc9e8bb5 100644
--- a/src/libslic3r/ExtrusionEntity.cpp
+++ b/src/libslic3r/ExtrusionEntity.cpp
@@ -7,11 +7,14 @@
 #include <cmath>
 #include <limits>
 #include <sstream>
+#include "Utils.hpp"
 
 #define L(s) (s)
 
 namespace Slic3r {
-    
+static const double slope_path_ratio = 0.3;
+static const double slope_inner_outer_wall_gap = 0.4;
+
 void ExtrusionPath::intersect_expolygons(const ExPolygons &collection, ExtrusionEntityCollection* retval) const
 {
     this->_inflate_collection(intersection_pl(Polylines{ polyline }, collection), retval);
@@ -306,6 +309,89 @@ void ExtrusionLoop::clip_end(double distance, ExtrusionPaths* paths) const
     }
 }
 
+// BBS: clipe slope a bit
+void ExtrusionLoopSloped::clip_slope(double distance, bool inter_perimeter)
+{
+
+    this->clip_end(distance);
+    this->clip_front(distance*2);
+}
+
+// BBS
+void ExtrusionLoopSloped::clip_end(const double distance)
+{
+    double clip_dist = distance;
+    std::vector<ExtrusionPathSloped> &ends_slope = this->ends;
+    while (clip_dist > 0) {
+        ExtrusionPathSloped &last_path = ends_slope.back();
+        double len = last_path.length();
+        if (len <= clip_dist) {
+            ends_slope.pop_back();
+            clip_dist -= len;
+        } else {
+            last_path.polyline.clip_end(clip_dist);
+            break;
+        }
+    }
+}
+
+// BBS
+void ExtrusionLoopSloped::clip_front(const double distance)
+{
+    double clip_dist = distance;
+    if (this->role() == erPerimeter)
+        clip_dist = scale_(this->slope_path_length()) * slope_inner_outer_wall_gap;
+
+    std::vector<ExtrusionPathSloped> &start_slope = this->starts;
+
+    Polyline front_inward;
+    while (distance > 0) {
+        ExtrusionPathSloped &first_path = start_slope.front();
+        double len = first_path.length();
+        if (len <= clip_dist) {
+            start_slope.erase(start_slope.begin());
+            clip_dist -= len;
+        } else {
+            first_path.polyline.reverse();
+            first_path.polyline.clip_end(clip_dist);
+            first_path.polyline.reverse();
+            break;
+        }
+    }
+}
+
+double ExtrusionLoopSloped::slope_path_length() {
+    double total_length = 0.0;
+    for (ExtrusionPathSloped start_ep : this->starts) {
+        total_length += unscale_(start_ep.length());
+    }
+    return total_length;
+}
+
+// BBS: slowdown slope path seep to get better seam
+void ExtrusionLoopSloped::slowdown_slope_speed() {
+    double speed_base   = slope_path_ratio * this->target_speed;
+    double speed_update = speed_base;
+    double count_length = 0.0;
+    double total_length = this->slope_path_length();
+
+    for (ExtrusionPathSloped &start_ep : this->starts) {
+        start_ep.slope_begin.speed_record = speed_update;
+        count_length += unscale_(start_ep.length());
+        // mapping speed for each path
+        start_ep.slope_end.speed_record = speed_base + (this->target_speed - speed_base) * (count_length / total_length);
+        speed_update = start_ep.slope_end.speed_record;
+    }
+
+    for (size_t ep_index = 0; ep_index < this->ends.size(); ++ep_index) {
+        ExtrusionPathSloped &end_ep = this->ends[ep_index];
+        ExtrusionPathSloped &start_ep = this->starts[this->starts.size() - 1 - ep_index];
+
+        end_ep.slope_begin.speed_record = start_ep.slope_end.speed_record;
+        end_ep.slope_end.speed_record = start_ep.slope_begin.speed_record;
+    }
+}
+
 bool ExtrusionLoop::has_overhang_point(const Point &point) const
 {
     for (const ExtrusionPath &path : this->paths) {
@@ -339,6 +425,158 @@ double ExtrusionLoop::min_mm3_per_mm() const
     return min_mm3_per_mm;
 }
 
+// Orca: This function is used to check if the loop is smooth(continuous) or not.
+// TODO: the main logic is largly copied from the calculate_polygon_angles_at_vertices function in SeamPlacer file. Need to refactor the code in the future.
+bool ExtrusionLoop::is_smooth(double angle_threshold, double min_arm_length) const
+{
+    // go through all the points in the loop and check if the angle between two segments(AB and BC) is less than the threshold
+    size_t idx_prev = 0;
+    size_t idx_curr = 0;
+    size_t idx_next = 0;
+
+    float distance_to_prev = 0;
+    float distance_to_next = 0;
+
+    const auto    _polygon = polygon();
+    const Points &points   = _polygon.points;
+
+    std::vector<float> lengths{};
+    for (size_t point_idx = 0; point_idx < points.size() - 1; ++point_idx) { lengths.push_back((unscale(points[point_idx]) - unscale(points[point_idx + 1])).norm()); }
+    lengths.push_back(std::max((unscale(points[0]) - unscale(points[points.size() - 1])).norm(), 0.1));
+
+    // push idx_prev far enough back as initialization
+    while (distance_to_prev < min_arm_length) {
+        idx_prev = Slic3r::prev_idx_modulo(idx_prev, points.size());
+        distance_to_prev += lengths[idx_prev];
+    }
+
+    for (size_t _i = 0; _i < points.size(); ++_i) {
+        // pull idx_prev to current as much as possible, while respecting the min_arm_length
+        while (distance_to_prev - lengths[idx_prev] > min_arm_length) {
+            distance_to_prev -= lengths[idx_prev];
+            idx_prev = Slic3r::next_idx_modulo(idx_prev, points.size());
+        }
+
+        // push idx_next forward as far as needed
+        while (distance_to_next < min_arm_length) {
+            distance_to_next += lengths[idx_next];
+            idx_next = Slic3r::next_idx_modulo(idx_next, points.size());
+        }
+
+        // Calculate angle between idx_prev, idx_curr, idx_next.
+        const Point &p0 = points[idx_prev];
+        const Point &p1 = points[idx_curr];
+        const Point &p2 = points[idx_next];
+        const auto   a  = angle(p0 - p1, p2 - p1);
+        if (a > 0 ? a < angle_threshold : a > -angle_threshold) { return false; }
+
+        // increase idx_curr by one
+        float curr_distance = lengths[idx_curr];
+        idx_curr++;
+        distance_to_prev += curr_distance;
+        distance_to_next -= curr_distance;
+    }
+
+    return true;
+}
+
+ExtrusionLoopSloped::ExtrusionLoopSloped( ExtrusionPaths &original_paths,
+                                          double seam_gap,
+                                          double slope_min_length,
+                                          double slope_max_segment_length,
+                                          double start_slope_ratio, ExtrusionLoopRole role)
+ : ExtrusionLoop(role)
+{
+    // create slopes
+    const auto add_slop = [this, slope_max_segment_length, seam_gap](const ExtrusionPath &path, const Polyline &poly, double ratio_begin, double ratio_end) {
+        if (poly.empty()) { return; }
+
+        // Ensure `slope_max_segment_length`
+        Polyline detailed_poly;
+        {
+            detailed_poly.append(poly.first_point());
+
+            // Recursively split the line into half until no longer than `slope_max_segment_length`
+            const std::function<void(const Line &)> handle_line = [slope_max_segment_length, &detailed_poly, &handle_line](const Line &line) {
+                if (line.length() <= slope_max_segment_length) {
+                    detailed_poly.append(line.b);
+                } else {
+                    // Then process left half
+                    handle_line({line.a, line.midpoint()});
+                    // Then process right half
+                    handle_line({line.midpoint(), line.b});
+                }
+            };
+
+            for (const auto &l : poly.lines()) { handle_line(l); }
+        }
+
+        starts.emplace_back(detailed_poly, path, ExtrusionPathSloped::Slope{ratio_begin, ratio_begin}, ExtrusionPathSloped::Slope{ratio_end, ratio_end});
+
+        if (is_approx(ratio_end, 1.) && seam_gap > 0) {
+            // Remove the segments that has no extrusion
+            const auto seg_length = detailed_poly.length();
+            if (seg_length > seam_gap) {
+                // Split the segment and remove the last `seam_gap` bit
+                const Polyline orig = detailed_poly;
+                Polyline       tmp;
+                orig.split_at_length(seg_length - seam_gap, &detailed_poly, &tmp);
+
+                ratio_end = lerp(ratio_begin, ratio_end, (seg_length - seam_gap) / seg_length);
+                assert(1. - ratio_end > EPSILON);
+            } else {
+                // Remove the entire segment
+                detailed_poly.clear();
+            }
+        }
+        if (!detailed_poly.empty()) { ends.emplace_back(detailed_poly, path, ExtrusionPathSloped::Slope{1., 1. - ratio_begin}, ExtrusionPathSloped::Slope{1., 1. - ratio_end}); }
+
+    };
+
+    double remaining_length = slope_min_length;
+
+    ExtrusionPaths::iterator path        = original_paths.begin();
+    double                   start_ratio = start_slope_ratio;
+    for (; path != original_paths.end() && remaining_length > 0; ++path) {
+        const double path_len = unscale_(path->length());
+        if (path_len > remaining_length) {
+            // Split current path into slope and non-slope part
+            Polyline slope_path;
+            Polyline flat_path;
+            path->polyline.split_at_length(scale_(remaining_length), &slope_path, &flat_path);
+
+            add_slop(*path, slope_path, start_ratio, 1);
+            start_ratio = 1;
+
+            paths.emplace_back(std::move(flat_path), *path);
+            remaining_length = 0;
+        } else {
+            remaining_length -= path_len;
+            const double end_ratio = lerp(1.0, start_slope_ratio, remaining_length / slope_min_length);
+            add_slop(*path, path->polyline, start_ratio, end_ratio);
+            start_ratio = end_ratio;
+        }
+    }
+    assert(remaining_length <= 0);
+    assert(start_ratio == 1.);
+
+    // Put remaining flat paths
+    paths.insert(paths.end(), path, original_paths.end());
+}
+
+std::vector<const ExtrusionPath *> ExtrusionLoopSloped::get_all_paths() const
+{
+    std::vector<const ExtrusionPath *> r;
+    r.reserve(starts.size() + paths.size() + ends.size());
+    for (const auto &p : starts)
+        r.push_back(&p);
+    for (const auto &p : paths)
+        r.push_back(&p);
+    for (const auto &p : ends)
+        r.push_back(&p);
+
+    return r;
+}
 
 std::string ExtrusionEntity::role_to_string(ExtrusionRole role)
 {
diff --git a/src/libslic3r/ExtrusionEntity.hpp b/src/libslic3r/ExtrusionEntity.hpp
index c1b48fd26..f2c21e83a 100644
--- a/src/libslic3r/ExtrusionEntity.hpp
+++ b/src/libslic3r/ExtrusionEntity.hpp
@@ -46,6 +46,7 @@ enum ExtrusionLoopRole {
     elrDefault,
     elrContourInternalPerimeter,
     elrSkirt,
+    elrPerimeterHole,
 };
 
 
@@ -285,6 +286,36 @@ private:
     bool m_no_extrusion = false;
 };
 
+class ExtrusionPathSloped : public ExtrusionPath
+{
+public:
+    struct Slope
+    {
+        double z_ratio{1.};
+        double e_ratio{1.};
+        double speed_record{0.0};
+    };
+
+    Slope slope_begin;
+    Slope slope_end;
+    ExtrusionPathSloped(const ExtrusionPath &rhs, const Slope &begin, const Slope &end) : ExtrusionPath(rhs), slope_begin(begin), slope_end(end) {}
+    ExtrusionPathSloped(ExtrusionPath &&rhs, const Slope &begin, const Slope &end) : ExtrusionPath(std::move(rhs)), slope_begin(begin), slope_end(end) {}
+    ExtrusionPathSloped(const Polyline &polyline, const ExtrusionPath &rhs, const Slope &begin, const Slope &end) : ExtrusionPath(polyline, rhs), slope_begin(begin), slope_end(end)
+    {}
+    ExtrusionPathSloped(Polyline &&polyline, const ExtrusionPath &rhs, const Slope &begin, const Slope &end) : ExtrusionPath(std::move(polyline), rhs), slope_begin(begin), slope_end(end)
+    {}
+
+    Slope interpolate(const double ratio) const {
+        return {
+            lerp(slope_begin.z_ratio, slope_end.z_ratio, ratio),
+            lerp(slope_begin.e_ratio, slope_end.e_ratio, ratio),
+            lerp(slope_begin.speed_record, slope_end.speed_record, ratio),
+        };
+    }
+
+    bool is_flat() const { return is_approx(slope_begin.z_ratio, slope_end.z_ratio); }
+};
+
 class ExtrusionPathOriented : public ExtrusionPath
 {
 public:
@@ -427,7 +458,8 @@ public:
             append(dst, p.polyline.points);
     }
     double total_volume() const override { double volume =0.; for (const auto& path : paths) volume += path.total_volume(); return volume; }
-
+    // check if the loop is smooth, angle_threshold is in radians, default is 10 degrees
+    bool is_smooth(double angle_threshold = 0.174, double min_arm_length = 0.025) const;
     //static inline std::string role_to_string(ExtrusionLoopRole role);
 
 #ifndef NDEBUG
@@ -443,6 +475,24 @@ private:
     ExtrusionLoopRole m_loop_role;
 };
 
+class ExtrusionLoopSloped : public ExtrusionLoop
+{
+public:
+    std::vector<ExtrusionPathSloped> starts;
+    std::vector<ExtrusionPathSloped> ends;
+    double target_speed{0.0};
+
+    ExtrusionLoopSloped(
+        ExtrusionPaths &original_paths, double seam_gap, double slope_min_length, double slope_max_segment_length, double start_slope_ratio, ExtrusionLoopRole role = elrDefault);
+
+    [[nodiscard]] std::vector<const ExtrusionPath *> get_all_paths() const;
+    void clip_slope(double distance, bool inter_perimeter = false );
+    void clip_end(const double distance);
+    void clip_front(const double distance);
+    double slope_path_length();
+    void slowdown_slope_speed();
+};
+
 inline void extrusion_paths_append(ExtrusionPaths &dst, Polylines &polylines, ExtrusionRole role, double mm3_per_mm, float width, float height)
 {
     dst.reserve(dst.size() + polylines.size());
diff --git a/src/libslic3r/GCode.cpp b/src/libslic3r/GCode.cpp
index 972f62ca8..8517cf8d9 100644
--- a/src/libslic3r/GCode.cpp
+++ b/src/libslic3r/GCode.cpp
@@ -3914,6 +3914,68 @@ static std::unique_ptr<EdgeGrid::Grid> calculate_layer_edge_grid(const Layer& la
     return out;
 }
 
+static bool has_overhang_path_on_slope(const ExtrusionLoop &loop, double slope_length)
+{
+    double count_length = 0.0;
+    for (ExtrusionPath path : loop.paths) {
+        if (count_length > slope_length)
+            return false;
+
+        if (path.overhang_degree > 1)
+            return true;
+
+        count_length += path.length();
+    }
+
+    return false;
+}
+
+double GCode::get_path_speed(const ExtrusionPath &path)
+{
+    double min_speed = double(m_config.slow_down_min_speed.get_at(m_writer.extruder()->id()));
+    // set speed
+    double speed = 0;
+    if (path.role() == erPerimeter) {
+        speed = m_config.get_abs_value("inner_wall_speed");
+        if (m_config.enable_overhang_speed.value) {
+            double new_speed = 0;
+            new_speed        = get_overhang_degree_corr_speed(speed, path.overhang_degree);
+            speed            = new_speed == 0.0 ? speed : new_speed;
+        }
+    } else if (path.role() == erExternalPerimeter) {
+        speed = m_config.get_abs_value("outer_wall_speed");
+        if (m_config.enable_overhang_speed.value) {
+            double new_speed = 0;
+            new_speed        = get_overhang_degree_corr_speed(speed, path.overhang_degree);
+            speed            = new_speed == 0.0 ? speed : new_speed;
+        }
+    } else if (path.role() == erOverhangPerimeter || path.role() == erBridgeInfill || path.role() == erSupportTransition) {
+        speed = m_config.get_abs_value("bridge_speed");
+    }
+    auto _mm3_per_mm = path.mm3_per_mm * double(m_curr_print->calib_mode() == CalibMode::Calib_Flow_Rate ? this->config().print_flow_ratio.value : 1);
+
+    // BBS: if not set the speed, then use the filament_max_volumetric_speed directly
+    if (speed == 0) {
+        if (_mm3_per_mm > 0)
+            speed = EXTRUDER_CONFIG(filament_max_volumetric_speed) / _mm3_per_mm;
+        else
+            speed = EXTRUDER_CONFIG(filament_max_volumetric_speed) / path.mm3_per_mm;
+    }
+    if (this->on_first_layer()) {
+        // BBS: for solid infill of initial layer, speed can be higher as long as
+        // wall lines have be attached
+        if (path.role() != erBottomSurface) speed = m_config.get_abs_value("initial_layer_speed");
+    }
+
+    if (EXTRUDER_CONFIG(filament_max_volumetric_speed) > 0) {
+        double extrude_speed = EXTRUDER_CONFIG(filament_max_volumetric_speed) / path.mm3_per_mm;
+        if (_mm3_per_mm > 0) extrude_speed = EXTRUDER_CONFIG(filament_max_volumetric_speed) / _mm3_per_mm;
+
+        // cap speed with max_volumetric_speed anyway (even if user is not using autospeed)
+        speed = std::min(speed, extrude_speed);
+    }
+    return speed;
+}
 
 std::string GCode::extrude_loop(ExtrusionLoop loop, std::string description, double speed)
 {
@@ -3922,7 +3984,7 @@ std::string GCode::extrude_loop(ExtrusionLoop loop, std::string description, dou
 
     // extrude all loops ccw
     bool was_clockwise = loop.make_counter_clockwise();
-
+    bool is_hole = loop.loop_role() == elrPerimeterHole;
     // find the point of the loop that is closest to the current extruder position
     // or randomize if requested
     Point last_pos = this->last_pos();
@@ -3933,14 +3995,25 @@ std::string GCode::extrude_loop(ExtrusionLoop loop, std::string description, dou
     } else
         loop.split_at(last_pos, false);
 
+    const auto seam_scarf_type   = m_config.seam_slope_type.value;
+    // BBS: not apply on fist layer, too small E has stick issue with hotend plate
+    bool enable_seam_slope = ((seam_scarf_type == SeamScarfType::External && !is_hole) ||
+                                    seam_scarf_type == SeamScarfType::All) &&
+                                    !m_config.spiral_mode &&
+                                    (loop.role() == erExternalPerimeter ||
+                                    (loop.role() == erPerimeter && m_config.seam_slope_inner_walls)) &&
+                                    !on_first_layer();
+
+    if (enable_seam_slope && m_config.seam_slope_conditional.value) {
+        enable_seam_slope = loop.is_smooth(m_config.scarf_angle_threshold.value * M_PI / 180., EXTRUDER_CONFIG(nozzle_diameter));
+    }
+
     // clip the path to avoid the extruder to get exactly on the first point of the loop;
     // if polyline was shorter than the clipping distance we'd get a null polyline, so
     // we discard it in that case
-    double clip_length = m_enable_loop_clipping ?
-        scale_(EXTRUDER_CONFIG(nozzle_diameter)) * ( m_config.seam_gap.value / 100 ) :
-        0;
-
-    // get paths
+    const double seam_gap    = scale_(EXTRUDER_CONFIG(nozzle_diameter)) * (m_config.seam_gap.value / 100);
+    const double clip_length = m_enable_loop_clipping && !enable_seam_slope ? seam_gap : 0;
+     // get paths
     ExtrusionPaths paths;
     loop.clip_end(clip_length, &paths);
     if (paths.empty()) return "";
@@ -3953,12 +4026,70 @@ std::string GCode::extrude_loop(ExtrusionLoop loop, std::string description, dou
     // extrude along the path
     std::string gcode;
     bool is_small_peri=false;
-    for (ExtrusionPaths::iterator path = paths.begin(); path != paths.end(); ++path) {
-//    description += ExtrusionLoop::role_to_string(loop.loop_role());
-//    description += ExtrusionEntity::role_to_string(path->role);
-    //BBS: Small perimeter has been considered in curva and overhang detection in speed generater.
-        is_small_peri=(small_peri_speed>0 && is_perimeter(path->role()) && !is_bridge(path->role()) && path->get_overhang_degree()==0);
-        gcode += this->_extrude(*path, description, is_small_peri?small_peri_speed:speed);
+
+    const auto  speed_for_path = [&speed, &small_peri_speed](const ExtrusionPath &path) {
+        // don't apply small perimeter setting for overhangs/bridges/non-perimeters
+        const bool is_small_peri = is_perimeter(path.role()) && !is_bridge(path.role()) && small_peri_speed > 0 &&
+                                   (path.get_overhang_degree() == 0 || path.get_overhang_degree() > 5);
+        return is_small_peri ? small_peri_speed : speed;
+    };
+
+    //BBS: avoid overhang on conditional scarf mode
+    bool slope_has_overhang = false;
+    if (enable_seam_slope) {
+        // Create seam slope
+        double start_slope_ratio;
+        if (m_config.seam_slope_start_height.percent) {
+            start_slope_ratio = m_config.seam_slope_start_height.value / 100.;
+        } else {
+            // Get the ratio against current layer height
+            double h          = paths.front().height;
+            start_slope_ratio = m_config.seam_slope_start_height.value / h;
+        }
+
+        double loop_length = 0.;
+        for (const auto &path : paths) {
+            loop_length += unscale_(path.length());
+        }
+        const bool   slope_entire_loop        = m_config.seam_slope_entire_loop;
+        const double slope_min_length         = slope_entire_loop ? loop_length : std::min(m_config.seam_slope_min_length.value, loop_length);
+        const int    slope_steps              = m_config.seam_slope_steps;
+        const double slope_max_segment_length = scale_(slope_min_length / slope_steps);
+        // BBS: check if has overhang on slope path
+        slope_has_overhang = has_overhang_path_on_slope(loop.paths, slope_min_length);
+        if (!slope_has_overhang) {
+            // Calculate the sloped loop
+            //BBS: should has smaller e at start to get better seam
+            ExtrusionLoopSloped new_loop(paths, seam_gap, slope_min_length, slope_max_segment_length, start_slope_ratio, loop.loop_role());
+
+            //BBS: clip end and start to get better seam
+            new_loop.clip_slope(seam_gap);
+            // BBS: slowdown speed to improve seam
+            new_loop.target_speed = get_path_speed(new_loop.starts.back());
+            new_loop.slowdown_slope_speed();
+            // Then extrude it
+            for (const auto &p : new_loop.get_all_paths()) {
+                gcode += this->_extrude(*p, description, speed_for_path(*p));
+            }
+
+            // Fix path for wipe
+            if (!new_loop.ends.empty()) {
+                paths.clear();
+                // The start slope part is ignored as it overlaps with the end part
+                paths.reserve(new_loop.paths.size() + new_loop.ends.size());
+                paths.insert(paths.end(), new_loop.paths.begin(), new_loop.paths.end());
+                paths.insert(paths.end(), new_loop.ends.begin(), new_loop.ends.end());
+            }
+        }
+    }
+
+    if (!enable_seam_slope || slope_has_overhang) {
+        if (enable_seam_slope)
+            paths.back().clip_end(seam_gap);
+
+        for (ExtrusionPaths::iterator path = paths.begin(); path != paths.end(); ++path) {
+            gcode += this->_extrude(*path, description, speed_for_path(*path));
+        }
     }
 
     //BBS: don't reset acceleration when printing first layer. During first layer, acceleration is always same value.
@@ -4271,21 +4402,28 @@ double GCode::get_overhang_degree_corr_speed(float normal_speed, double path_deg
     return speed_out;
 }
 
-std::string GCode::_extrude(const ExtrusionPath &path, std::string description, double speed)
+std::string GCode::_extrude(const ExtrusionPath &path, std::string description, double speed, bool is_first_slope)
 {
     std::string gcode;
 
     if (is_bridge(path.role()))
         description += " (bridge)";
 
+    const ExtrusionPathSloped *sloped = dynamic_cast<const ExtrusionPathSloped *>(&path);
+    const auto get_sloped_z = [&sloped, this](double z_ratio) {
+        const auto height = sloped->height; 
+        return lerp(m_nominal_z - height, m_nominal_z, z_ratio);
+    };
+
     // go to first point of extrusion path
     //BBS: path.first_point is 2D point. But in lazy raise case, lift z is done in travel_to function.
     //Add m_need_change_layer_lift_z when change_layer in case of no lift if m_last_pos is equal to path.first_point() by chance
-    if (!m_last_pos_defined || m_last_pos != path.first_point() || m_need_change_layer_lift_z) {
+    if (!m_last_pos_defined || m_last_pos != path.first_point() || m_need_change_layer_lift_z || (sloped != nullptr && !sloped->is_flat())) {
         gcode += this->travel_to(
             path.first_point(),
             path.role(),
-            "move to first " + description + " point"
+            "move to first " + description + " point",
+            sloped == nullptr ? DBL_MAX : get_sloped_z(sloped->slope_begin.z_ratio)
         );
         m_need_change_layer_lift_z = false;
     }
@@ -4499,7 +4637,9 @@ std::string GCode::_extrude(const ExtrusionPath &path, std::string description,
     }
 
     // F is mm per minute.
-    gcode += m_writer.set_speed(F, "", comment);
+    if (sloped == nullptr)
+        gcode += m_writer.set_speed(F, "", comment);
+
     double path_length = 0.;
     {
         std::string comment = GCodeWriter::full_gcode_comment ? description : "";
@@ -4507,14 +4647,30 @@ std::string GCode::_extrude(const ExtrusionPath &path, std::string description,
         //Attention: G2 and G3 is not supported in spiral_mode mode
         if (!m_config.enable_arc_fitting ||
             path.polyline.fitting_result.empty() ||
-            m_config.spiral_mode) {
-            for (const Line& line : path.polyline.lines()) {
+            m_config.spiral_mode ||
+            sloped != nullptr) {
+            double path_length  = 0.;
+            double total_length = sloped == nullptr ? 0. : path.polyline.length() * SCALING_FACTOR;
+            for (const Line &line : path.polyline.lines()) {
                 const double line_length = line.length() * SCALING_FACTOR;
                 path_length += line_length;
-                gcode += m_writer.extrude_to_xy(
-                    this->point_to_gcode(line.b),
-                    e_per_mm * line_length,
-                    comment);
+
+                if (sloped == nullptr) {
+                    gcode += m_writer.extrude_to_xy(
+                        this->point_to_gcode(line.b),
+                        e_per_mm * line_length,
+                        comment);
+                } else {
+                    // Sloped extrusion
+                    auto dE = e_per_mm * line_length;
+                    auto [z_ratio, e_ratio, slope_speed] = sloped->interpolate(path_length / total_length);
+                    gcode += m_writer.set_speed(slope_speed * 60, "", comment);
+                    Vec2d dest2d = this->point_to_gcode(line.b);
+                    Vec3d dest3d(dest2d(0), dest2d(1), get_sloped_z(z_ratio));
+                    //BBS: todo, should use small e at start to get good seam
+                    double slope_e = dE * e_ratio;
+                    gcode += m_writer.extrude_to_xyz(dest3d, slope_e);
+                }
             }
         } else {
             // BBS: start to generate gcode from arc fitting data which includes line and arc
@@ -4613,7 +4769,7 @@ std::string GCode::_encode_label_ids_to_base64(std::vector<size_t> ids)
 }
 
 // This method accepts &point in print coordinates.
-std::string GCode::travel_to(const Point &point, ExtrusionRole role, std::string comment)
+std::string GCode::travel_to(const Point &point, ExtrusionRole role, std::string comment, double z )
 {
     /*  Define the travel move as a line between current position and the taget point.
         This is expressed in print coordinates, so it will need to be translated by
@@ -4691,6 +4847,37 @@ std::string GCode::travel_to(const Point &point, ExtrusionRole role, std::string
                 gcode += m_writer.travel_to_xy(this->point_to_gcode(travel.points[i]), comment);
             }
         }
+        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);
+        } 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);
+            } 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
+                for (size_t i = 1; i < travel.size(); ++i) {
+                    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_nominal_z);
+                        gcode += m_writer.travel_to_xyz(dest3d, comment);
+                    } 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);
+                    } else {
+                        // For all points in between, no z change
+                        gcode += m_writer.travel_to_xy(this->point_to_gcode(travel.points[i]), comment );
+                    }
+                }
+            }
+        }
         this->set_last_pos(travel.points.back());
     }
 
diff --git a/src/libslic3r/GCode.hpp b/src/libslic3r/GCode.hpp
index dcbd3d144..79ee6dcbc 100644
--- a/src/libslic3r/GCode.hpp
+++ b/src/libslic3r/GCode.hpp
@@ -410,7 +410,7 @@ private:
     std::string     extrude_infill(const Print &print, const std::vector<ObjectByExtruder::Island::Region> &by_region, bool ironing);
     std::string     extrude_support(const ExtrusionEntityCollection &support_fills);
 
-    std::string     travel_to(const Point &point, ExtrusionRole role, std::string comment);
+    std::string travel_to(const Point &point, ExtrusionRole role, std::string comment, double z = DBL_MAX);
     // BBS
     LiftType to_lift_type(ZHopType z_hop_types);
 
@@ -512,7 +512,8 @@ private:
     // BBS
     int get_bed_temperature(const int extruder_id, const bool is_first_layer, const BedType bed_type) const;
 
-    std::string _extrude(const ExtrusionPath &path, std::string description = "", double speed = -1);
+    std::string _extrude(const ExtrusionPath &path, std::string description = "", double speed = -1, bool is_first_slope = false);
+    double get_path_speed(const ExtrusionPath &path);
     double get_overhang_degree_corr_speed(float speed, double path_degree);
     void print_machine_envelope(GCodeOutputStream &file, Print &print);
     void _print_first_layer_bed_temperature(GCodeOutputStream &file, Print &print, const std::string &gcode, unsigned int first_printing_extruder_id, bool wait);
diff --git a/src/libslic3r/GCode/GCodeProcessor.cpp b/src/libslic3r/GCode/GCodeProcessor.cpp
index 1dae839a2..4df452149 100644
--- a/src/libslic3r/GCode/GCodeProcessor.cpp
+++ b/src/libslic3r/GCode/GCodeProcessor.cpp
@@ -1004,8 +1004,11 @@ void GCodeProcessor::apply_config(const PrintConfig& config)
 
     const ConfigOptionBool* spiral_vase = config.option<ConfigOptionBool>("spiral_mode");
     if (spiral_vase != nullptr)
-        m_spiral_vase_active = spiral_vase->value;
+        m_detect_layer_based_on_tag  = spiral_vase->value;
 
+    const ConfigOptionBool *has_scarf_joint_seam = config.option<ConfigOptionBool>("has_scarf_joint_seam");
+    if (has_scarf_joint_seam != nullptr)
+        m_detect_layer_based_on_tag  = m_detect_layer_based_on_tag  || has_scarf_joint_seam->value;
 
 }
 
@@ -1286,7 +1289,11 @@ void GCodeProcessor::apply_config(const DynamicPrintConfig& config)
 
     const ConfigOptionBool* spiral_vase = config.option<ConfigOptionBool>("spiral_mode");
     if (spiral_vase != nullptr)
-        m_spiral_vase_active = spiral_vase->value;
+        m_detect_layer_based_on_tag  = spiral_vase->value;
+
+    const ConfigOptionBool *has_scarf_joint_seam = config.option<ConfigOptionBool>("has_scarf_joint_seam");
+    if (has_scarf_joint_seam != nullptr)
+        m_detect_layer_based_on_tag = m_detect_layer_based_on_tag || has_scarf_joint_seam->value;
 
     const ConfigOptionEnumGeneric *bed_type = config.option<ConfigOptionEnumGeneric>("curr_bed_type");
     if (bed_type != nullptr)
@@ -1363,8 +1370,9 @@ void GCodeProcessor::reset()
 
     m_options_z_corrector.reset();
 
-    m_spiral_vase_active = false;
+    m_detect_layer_based_on_tag = false;
 
+    m_seams_count = 0;
 #if ENABLE_GCODE_VIEWER_DATA_CHECKING
     m_mm3_per_mm_compare.reset();
     m_height_compare.reset();
@@ -2222,12 +2230,12 @@ void GCodeProcessor::process_tags(const std::string_view comment, bool producers
     // layer change tag
     if (comment == reserved_tag(ETags::Layer_Change)) {
         ++m_layer_id;
-        if (m_spiral_vase_active) {
+        if (m_detect_layer_based_on_tag) {
             if (m_result.moves.empty() || m_result.spiral_vase_layers.empty())
                 // add a placeholder for layer height. the actual value will be set inside process_G1() method
                 m_result.spiral_vase_layers.push_back({ FLT_MAX, { 0, 0 } });
             else {
-                const size_t move_id = m_result.moves.size() - 1;
+                const size_t move_id = m_result.moves.size() - 1 - m_seams_count;
                 if (!m_result.spiral_vase_layers.empty())
                     m_result.spiral_vase_layers.back().second.second = move_id;
                 // add a placeholder for layer height. the actual value will be set inside process_G1() method
@@ -3090,6 +3098,15 @@ void GCodeProcessor::process_G1(const GCodeReader::GCodeLine& line)
             //BBS: m_result.moves.back().position has plate offset, must minus plate offset before calculate the real seam position
             const Vec3f real_first_pos = Vec3f(m_result.moves.back().position.x() - m_x_offset, m_result.moves.back().position.y() - m_y_offset, m_result.moves.back().position.z());
             m_seams_detector.set_first_vertex(real_first_pos - m_extruder_offsets[m_extruder_id]);
+        } else if (type == EMoveType::Extrude && m_extrusion_role == erExternalPerimeter && m_detect_layer_based_on_tag) {
+            const Vec3f real_last_pos = Vec3f(m_result.moves.back().position.x() - m_x_offset, m_result.moves.back().position.y() - m_y_offset,
+                                              m_result.moves.back().position.z());
+            const Vec3f new_pos       = real_last_pos - m_extruder_offsets[m_extruder_id];
+            // We may have sloped loop, drop any previous start pos if we have z increment
+            const std::optional<Vec3f> first_vertex = m_seams_detector.get_first_vertex();
+            if (new_pos.z() > first_vertex->z()) {
+                m_seams_detector.set_first_vertex(new_pos);
+            }
         }
         // check for seam ending vertex and store the resulting move
         else if ((type != EMoveType::Extrude || (m_extrusion_role != erExternalPerimeter && m_extrusion_role != erOverhangPerimeter)) && m_seams_detector.has_first_vertex()) {
@@ -3119,7 +3136,7 @@ void GCodeProcessor::process_G1(const GCodeReader::GCodeLine& line)
         m_seams_detector.set_first_vertex(m_result.moves.back().position - m_extruder_offsets[m_extruder_id] - plate_offset);
     }
 
-    if (m_spiral_vase_active && !m_result.spiral_vase_layers.empty()) {
+    if (m_detect_layer_based_on_tag && !m_result.spiral_vase_layers.empty()) {
         if (m_result.spiral_vase_layers.back().first == FLT_MAX && delta_pos[Z] > 0.0)
             // replace layer height placeholder with correct value
             m_result.spiral_vase_layers.back().first = static_cast<float>(m_end_position[Z]);
@@ -3508,6 +3525,13 @@ void  GCodeProcessor::process_G2_G3(const GCodeReader::GCodeLine& line)
         //BBS: check for seam starting vertex
         if (type == EMoveType::Extrude && m_extrusion_role == erExternalPerimeter && !m_seams_detector.has_first_vertex()) {
             m_seams_detector.set_first_vertex(m_result.moves.back().position - m_extruder_offsets[m_extruder_id] - plate_offset);
+        } else if (type == EMoveType::Extrude && m_extrusion_role == erExternalPerimeter && m_detect_layer_based_on_tag) {
+            const Vec3f real_last_pos = Vec3f(m_result.moves.back().position.x() - m_x_offset, m_result.moves.back().position.y() - m_y_offset,
+                                              m_result.moves.back().position.z());
+            const Vec3f new_pos       = real_last_pos - m_extruder_offsets[m_extruder_id];
+            // We may have sloped loop, drop any previous start pos if we have z increment
+            const std::optional<Vec3f> first_vertex = m_seams_detector.get_first_vertex();
+            if (new_pos.z() > first_vertex->z()) { m_seams_detector.set_first_vertex(new_pos); }
         }
         //BBS: check for seam ending vertex and store the resulting move
         else if ((type != EMoveType::Extrude || (m_extrusion_role != erExternalPerimeter && m_extrusion_role != erOverhangPerimeter)) && m_seams_detector.has_first_vertex()) {
@@ -4132,6 +4156,10 @@ void GCodeProcessor::store_move_vertex(EMoveType type, EMovePathType path_type)
         m_interpolation_points,
     });
 
+    if (type == EMoveType::Seam) {
+        m_seams_count++;
+    }
+
     // stores stop time placeholders for later use
     if (type == EMoveType::Color_change || type == EMoveType::Pause_Print) {
         for (size_t i = 0; i < static_cast<size_t>(PrintEstimatedStatistics::ETimeMode::Count); ++i) {
diff --git a/src/libslic3r/GCode/GCodeProcessor.hpp b/src/libslic3r/GCode/GCodeProcessor.hpp
index 39634b4a7..a0082ccd7 100644
--- a/src/libslic3r/GCode/GCodeProcessor.hpp
+++ b/src/libslic3r/GCode/GCodeProcessor.hpp
@@ -693,7 +693,8 @@ namespace Slic3r {
         SeamsDetector m_seams_detector;
         OptionsZCorrector m_options_z_corrector;
         size_t m_last_default_color_id;
-        bool m_spiral_vase_active;
+        bool m_detect_layer_based_on_tag {false};
+        int m_seams_count;
 #if ENABLE_GCODE_VIEWER_STATISTICS
         std::chrono::time_point<std::chrono::high_resolution_clock> m_start_time;
 #endif // ENABLE_GCODE_VIEWER_STATISTICS
@@ -762,6 +763,11 @@ namespace Slic3r {
 
         //BBS: set offset for gcode writer
         void set_xy_offset(double x, double y) { m_x_offset = x; m_y_offset = y; }
+        // Orca: if true, only change new layer if ETags::Layer_Change occurs
+        // otherwise when we got a lift of z during extrusion, a new layer will be added
+        void detect_layer_based_on_tag(bool enabled) {
+            m_detect_layer_based_on_tag = enabled;
+        }
 
     private:
         void apply_config(const DynamicPrintConfig& config);
diff --git a/src/libslic3r/Layer.cpp b/src/libslic3r/Layer.cpp
index d8a86aa9a..026530198 100644
--- a/src/libslic3r/Layer.cpp
+++ b/src/libslic3r/Layer.cpp
@@ -178,7 +178,15 @@ void Layer::make_perimeters()
 		                && config.infill_wall_overlap              == other_config.infill_wall_overlap
                         && config.fuzzy_skin                  == other_config.fuzzy_skin
                         && config.fuzzy_skin_thickness        == other_config.fuzzy_skin_thickness
-                        && config.fuzzy_skin_point_distance       == other_config.fuzzy_skin_point_distance)
+                        && config.fuzzy_skin_point_distance       == other_config.fuzzy_skin_point_distance
+                        && config.seam_slope_type         == other_config.seam_slope_type
+                        && config.seam_slope_conditional == other_config.seam_slope_conditional
+                        && config.scarf_angle_threshold  == other_config.scarf_angle_threshold
+                        && config.seam_slope_start_height == other_config.seam_slope_start_height
+                        && config.seam_slope_entire_loop  == other_config.seam_slope_entire_loop
+                        && config.seam_slope_min_length   == other_config.seam_slope_min_length
+                        && config.seam_slope_steps        == other_config.seam_slope_steps
+                        && config.seam_slope_inner_walls  == other_config.seam_slope_inner_walls)
 		            {
 			 			other_layerm->perimeters.clear();
 			 			other_layerm->fills.clear();
diff --git a/src/libslic3r/PerimeterGenerator.cpp b/src/libslic3r/PerimeterGenerator.cpp
index 26d97a2d4..7dc4c613b 100644
--- a/src/libslic3r/PerimeterGenerator.cpp
+++ b/src/libslic3r/PerimeterGenerator.cpp
@@ -416,7 +416,7 @@ static ExtrusionEntityCollection traverse_loops(const PerimeterGenerator &perime
             // there's only one contour loop).
             loop_role = elrContourInternalPerimeter;
         } else {
-            loop_role = elrDefault;
+            loop_role = loop.is_contour? elrDefault: elrPerimeterHole;
         }
         
         // detect overhanging/bridging perimeters
@@ -961,7 +961,7 @@ static ExtrusionEntityCollection traverse_extrusions(const PerimeterGenerator& p
         // Append paths to collection.
         if (!paths.empty()) {
             if (extrusion->is_closed) {
-                ExtrusionLoop extrusion_loop(std::move(paths));
+                ExtrusionLoop extrusion_loop(std::move(paths), extrusion->is_contour()? elrDefault : elrPerimeterHole);
                 // Restore the orientation of the extrusion loop.
                 if (pg_extrusion.is_contour)
                     extrusion_loop.make_counter_clockwise();
diff --git a/src/libslic3r/Polyline.cpp b/src/libslic3r/Polyline.cpp
index 383e36604..783f91229 100644
--- a/src/libslic3r/Polyline.cpp
+++ b/src/libslic3r/Polyline.cpp
@@ -297,6 +297,51 @@ bool Polyline::split_at_index(const size_t index, Polyline* p1, Polyline* p2) co
     return true;
 }
 
+bool Polyline::split_at_length(const double length, Polyline *p1, Polyline *p2) const
+{
+    if (this->points.empty()) return false;
+    if (length < 0 || length > this->length()) { return false; }
+
+    if (length < SCALED_EPSILON) {
+        p1->clear();
+        p1->append(this->first_point());
+        *p2 = *this;
+    } else if (is_approx(length, this->length(), SCALED_EPSILON)) {
+        p2->clear();
+        p2->append(this->last_point());
+        *p1 = *this;
+    } else {
+        // 1 find the line to split at
+        size_t line_idx   = 0;
+        double acc_length = 0;
+        Point  p          = this->first_point();
+        for (const auto &l : this->lines()) {
+            p = l.b;
+
+            const double current_length = l.length();
+            if (acc_length + current_length >= length) {
+                p = lerp(l.a, l.b, (length - acc_length) / current_length);
+                break;
+            }
+            acc_length += current_length;
+            line_idx++;
+        }
+
+        // 2 judge whether the cloest point is one vertex of polyline.
+        //  and spilit the polyline at different index
+        int index = this->find_point(p);
+        if (index != -1) {
+            this->split_at_index(index, p1, p2);
+        } else {
+            Polyline temp;
+            this->split_at_index(line_idx, p1, &temp);
+            p1->append(p);
+            this->split_at_index(line_idx + 1, &temp, p2);
+            p2->append_before(p);
+        }
+    }
+    return true;
+}
 
 bool Polyline::is_straight() const
 {
diff --git a/src/libslic3r/Polyline.hpp b/src/libslic3r/Polyline.hpp
index ccd89bb2f..320a98fef 100644
--- a/src/libslic3r/Polyline.hpp
+++ b/src/libslic3r/Polyline.hpp
@@ -120,7 +120,7 @@ public:
 //    template <class T> void simplify_by_visibility(const T &area);
     void split_at(Point &point, Polyline* p1, Polyline* p2) const;
     bool split_at_index(const size_t index, Polyline* p1, Polyline* p2) const;
-
+    bool split_at_length(const double length, Polyline *p1, Polyline *p2) const;
     bool is_straight() const;
     bool is_closed() const { return this->points.front() == this->points.back(); }
 
diff --git a/src/libslic3r/Preset.cpp b/src/libslic3r/Preset.cpp
index db0287032..67f6a62ea 100644
--- a/src/libslic3r/Preset.cpp
+++ b/src/libslic3r/Preset.cpp
@@ -845,8 +845,8 @@ static std::vector<std::string> s_Preset_print_options {
      // calib
     "print_flow_ratio",
     //Orca
-    "exclude_object"
-};
+    "exclude_object", "seam_slope_type", "seam_slope_conditional", "scarf_angle_threshold", "seam_slope_start_height", "seam_slope_entire_loop", "seam_slope_min_length",
+    "seam_slope_steps", "seam_slope_inner_walls"};
 
 static std::vector<std::string> s_Preset_filament_options {
     /*"filament_colour", */ "default_filament_colour","required_nozzle_HRC","filament_diameter", "filament_type", "filament_soluble", "filament_is_support",
diff --git a/src/libslic3r/PrintApply.cpp b/src/libslic3r/PrintApply.cpp
index a16653f03..54aa20a00 100644
--- a/src/libslic3r/PrintApply.cpp
+++ b/src/libslic3r/PrintApply.cpp
@@ -1042,6 +1042,26 @@ Print::ApplyStatus Print::apply(const Model &model, DynamicPrintConfig new_full_
     else
         m_support_used = false;
 
+    {
+        const auto &o = model.objects;
+        const auto opt_has_scarf_joint_seam = [](const DynamicConfig &c) {
+            return c.has("seam_slope_type") && c.opt_enum<SeamScarfType>("seam_slope_type") != SeamScarfType::None;
+        };
+        const bool has_scarf_joint_seam = std::any_of(o.begin(), o.end(), [&new_full_config, &opt_has_scarf_joint_seam](ModelObject *obj) {
+            return obj->get_config_value<ConfigOptionEnum<SeamScarfType>>(new_full_config, "seam_slope_type")->value != SeamScarfType::None ||
+                   std::any_of(obj->volumes.begin(), obj->volumes.end(),
+                               [&opt_has_scarf_joint_seam](const ModelVolume *v) { return opt_has_scarf_joint_seam(v->config.get()); }) ||
+                   std::any_of(obj->layer_config_ranges.begin(), obj->layer_config_ranges.end(),
+                               [&opt_has_scarf_joint_seam](const auto &r) { return opt_has_scarf_joint_seam(r.second.get()); });
+        });
+
+        if (has_scarf_joint_seam) {
+            new_full_config.set("has_scarf_joint_seam", true);
+        }
+
+        BOOST_LOG_TRIVIAL(info) << __FUNCTION__ << ", has_scarf_joint_seam:" << has_scarf_joint_seam;
+    }
+
     // Find modified keys of the various configs. Resolve overrides extruder retract values by filament profiles.
     DynamicPrintConfig   filament_overrides;
     //BBS: add plate index
diff --git a/src/libslic3r/PrintConfig.cpp b/src/libslic3r/PrintConfig.cpp
index 368b2b2fa..94ebd8e54 100644
--- a/src/libslic3r/PrintConfig.cpp
+++ b/src/libslic3r/PrintConfig.cpp
@@ -233,6 +233,15 @@ static t_config_enum_values s_keys_map_SeamPosition {
 };
 CONFIG_OPTION_ENUM_DEFINE_STATIC_MAPS(SeamPosition)
 
+
+// Orca
+static t_config_enum_values s_keys_map_SeamScarfType{
+    {"none",     int(SeamScarfType::None)},
+    {"external", int(SeamScarfType::External)},
+    {"all",      int(SeamScarfType::All)},
+};
+CONFIG_OPTION_ENUM_DEFINE_STATIC_MAPS(SeamScarfType)
+
 static const t_config_enum_values s_keys_map_SLADisplayOrientation = {
     { "landscape",      sladoLandscape},
     { "portrait",       sladoPortrait}
@@ -2227,6 +2236,10 @@ void PrintConfigDef::init_fff_params()
     def->mode = comAdvanced;
     def->set_default_value(new ConfigOptionString(""));
 
+    def = this->add("has_scarf_joint_seam", coBool);
+    def->mode = comAdvanced;
+    def->set_default_value(new ConfigOptionBool(false));
+
     {
         struct AxisDefault {
             std::string         name;
@@ -2799,6 +2812,70 @@ void PrintConfigDef::init_fff_params()
     def->mode = comDevelop;
     def->set_default_value(new ConfigOptionPercent(15));
 
+    def                = this->add("seam_slope_type", coEnum);
+    def->label         = L("Scarf joint seam (beta)");
+    def->tooltip       = L("Use scarf joint to minimize seam visibility and increase seam strength.");
+    def->enum_keys_map = &ConfigOptionEnum<SeamScarfType>::get_enum_values();
+    def->enum_values.push_back("none");
+    def->enum_values.push_back("external");
+    def->enum_values.push_back("all");
+    def->enum_labels.push_back(L("None"));
+    def->enum_labels.push_back(L("Contour"));
+    def->enum_labels.push_back(L("Contour and hole"));
+    def->mode = comAdvanced;
+    def->set_default_value(new ConfigOptionEnum<SeamScarfType>(SeamScarfType::All));
+
+    def          = this->add("seam_slope_conditional", coBool);
+    def->label   = L("Conditional scarf joint");
+    def->tooltip = L("Apply scarf joints only to smooth perimeters where traditional seams do not conceal the seams at sharp corners effectively.");
+    def->mode    = comAdvanced;
+    def->set_default_value(new ConfigOptionBool(true));
+
+    def           = this->add("scarf_angle_threshold", coInt);
+    def->label    = L("Conditional angle threshold");
+    def->tooltip  = L("This option sets the threshold angle for applying a conditional scarf joint seam.\nIf the maximum angle within the perimeter loop " "exceeds this value (indicating the absence of sharp corners), a scarf joint seam will be used. The default value is 155°.");
+    def->mode     = comAdvanced;
+    def->sidetext = L("°");
+    def->min      = 0;
+    def->max      = 180;
+    def->set_default_value(new ConfigOptionInt(155));
+
+    def           = this->add("seam_slope_start_height", coFloatOrPercent);
+    def->label    = L("Scarf start height");
+    def->tooltip  = L("Start height of the scarf.\n"
+                     "This amount can be specified in millimeters or as a percentage of the current layer height. The default value for this parameter is 0.");
+    def->sidetext = L("mm or %");
+    def->min      = 0;
+    def->mode     = comAdvanced;
+    def->set_default_value(new ConfigOptionFloatOrPercent(0.1, false));
+
+    def          = this->add("seam_slope_entire_loop", coBool);
+    def->label   = L("Scarf around entire wall");
+    def->tooltip = L("The scarf extends to the entire length of the wall.");
+    def->mode    = comAdvanced;
+    def->set_default_value(new ConfigOptionBool(false));
+
+    def           = this->add("seam_slope_min_length", coFloat);
+    def->label    = L("Scarf length");
+    def->tooltip  = L("Length of the scarf. Setting this parameter to zero effectively disables the scarf.");
+    def->sidetext = L("mm");
+    def->min      = 0;
+    def->mode     = comAdvanced;
+    def->set_default_value(new ConfigOptionFloat(10));
+
+    def          = this->add("seam_slope_steps", coInt);
+    def->label   = L("Scarf steps");
+    def->tooltip = L("Minimum number of segments of each scarf.");
+    def->min     = 1;
+    def->mode    = comAdvanced;
+    def->set_default_value(new ConfigOptionInt(10));
+
+    def          = this->add("seam_slope_inner_walls", coBool);
+    def->label   = L("Scarf joint for inner walls");
+    def->tooltip = L("Use scarf joint for inner walls as well.");
+    def->mode    = comAdvanced;
+    def->set_default_value(new ConfigOptionBool(true));
+
     def = this->add("wipe_speed", coPercent);
     def->label = L("Wipe speed");
     def->tooltip = L("The wipe speed is determined by the speed setting specified in this configuration." "If the value is expressed as a percentage (e.g. 80%), it will be calculated based on the travel speed setting above." "The default value for this parameter is 80%");
diff --git a/src/libslic3r/PrintConfig.hpp b/src/libslic3r/PrintConfig.hpp
index fc7a0103b..2711db044 100644
--- a/src/libslic3r/PrintConfig.hpp
+++ b/src/libslic3r/PrintConfig.hpp
@@ -137,6 +137,13 @@ enum SeamPosition {
     spNearest, spAligned, spRear, spRandom
 };
 
+// Orca
+enum class SeamScarfType {
+    None,
+    External,
+    All,
+};
+
 enum SLAMaterial {
     slamTough,
     slamFlex,
@@ -330,6 +337,7 @@ CONFIG_OPTION_ENUM_DECLARE_STATIC_MAPS(SupportMaterialInterfacePattern)
 // BBS
 CONFIG_OPTION_ENUM_DECLARE_STATIC_MAPS(SupportType)
 CONFIG_OPTION_ENUM_DECLARE_STATIC_MAPS(SeamPosition)
+CONFIG_OPTION_ENUM_DECLARE_STATIC_MAPS(SeamScarfType)
 CONFIG_OPTION_ENUM_DECLARE_STATIC_MAPS(SLADisplayOrientation)
 CONFIG_OPTION_ENUM_DECLARE_STATIC_MAPS(SLAPillarConnectionMode)
 CONFIG_OPTION_ENUM_DECLARE_STATIC_MAPS(BrimType)
@@ -821,7 +829,17 @@ PRINT_CONFIG_CLASS_DEFINE(
     ((ConfigOptionFloat, initial_layer_flow_ratio))
     ((ConfigOptionFloat, filter_out_gap_fill))
     //calib
-    ((ConfigOptionFloat, print_flow_ratio)))
+    ((ConfigOptionFloat, print_flow_ratio))
+    // Orca: seam slopes
+    ((ConfigOptionEnum<SeamScarfType>,  seam_slope_type))
+    ((ConfigOptionBool,                 seam_slope_conditional))
+    ((ConfigOptionInt,                  scarf_angle_threshold))
+    ((ConfigOptionFloatOrPercent,       seam_slope_start_height))
+    ((ConfigOptionBool,                 seam_slope_entire_loop))
+    ((ConfigOptionFloat,                seam_slope_min_length))
+    ((ConfigOptionInt,                  seam_slope_steps))
+    ((ConfigOptionBool,                 seam_slope_inner_walls))
+)
 
 PRINT_CONFIG_CLASS_DEFINE(
     MachineEnvelopeConfig,
@@ -926,6 +944,8 @@ PRINT_CONFIG_CLASS_DEFINE(
     ((ConfigOptionBool,                accel_to_decel_enable))
     ((ConfigOptionPercent,             accel_to_decel_factor))
     ((ConfigOptionEnumsGeneric,        extruder_type))
+    //Orca
+    ((ConfigOptionBool,                has_scarf_joint_seam))
 )
 
 // This object is mapped to Perl as Slic3r::Config::Print.
diff --git a/src/libslic3r/PrintObject.cpp b/src/libslic3r/PrintObject.cpp
index 0b13215a2..8e19621ca 100644
--- a/src/libslic3r/PrintObject.cpp
+++ b/src/libslic3r/PrintObject.cpp
@@ -902,6 +902,14 @@ bool PrintObject::invalidate_state_by_config_options(
             steps.emplace_back(posSlice);
         } else if (
                opt_key == "seam_position"
+            || opt_key == "seam_slope_type"
+            || opt_key == "seam_slope_conditional"
+            || opt_key == "scarf_angle_threshold"
+            || opt_key == "seam_slope_start_height"
+            || opt_key == "seam_slope_entire_loop"
+            || opt_key == "seam_slope_min_length"
+            || opt_key == "seam_slope_steps"
+            || opt_key == "seam_slope_inner_walls"
             || opt_key == "seam_gap"
             || opt_key == "wipe_speed"
             || opt_key == "support_speed"
diff --git a/src/slic3r/GUI/ConfigManipulation.cpp b/src/slic3r/GUI/ConfigManipulation.cpp
index 8a453eeb0..fbc444a4d 100644
--- a/src/slic3r/GUI/ConfigManipulation.cpp
+++ b/src/slic3r/GUI/ConfigManipulation.cpp
@@ -724,6 +724,17 @@ void ConfigManipulation::toggle_print_fff_options(DynamicPrintConfig *config, co
         toggle_field("accel_to_decel_factor", config->opt_bool("accel_to_decel_enable"));
     }
     toggle_line("exclude_object", gcflavor == gcfKlipper);
+
+    toggle_field("seam_slope_type", !has_spiral_vase);
+    bool has_seam_slope = !has_spiral_vase && config->opt_enum<SeamScarfType>("seam_slope_type") != SeamScarfType::None;
+    toggle_line("seam_slope_conditional", has_seam_slope);
+    toggle_line("scarf_angle_threshold", has_seam_slope && config->opt_bool("seam_slope_conditional"));
+    toggle_line("seam_slope_start_height", has_seam_slope);
+    toggle_line("seam_slope_entire_loop", has_seam_slope);
+    toggle_line("seam_slope_min_length", has_seam_slope);
+    toggle_line("seam_slope_steps", has_seam_slope);
+    toggle_line("seam_slope_inner_walls", has_seam_slope);
+    toggle_field("seam_slope_min_length", !config->opt_bool("seam_slope_entire_loop"));
 }
 
 void ConfigManipulation::update_print_sla_config(DynamicPrintConfig* config, const bool is_global_config/* = false*/)
diff --git a/src/slic3r/GUI/Tab.cpp b/src/slic3r/GUI/Tab.cpp
index a24f94fde..587e2b8b8 100644
--- a/src/slic3r/GUI/Tab.cpp
+++ b/src/slic3r/GUI/Tab.cpp
@@ -1904,6 +1904,14 @@ void TabPrint::build()
         optgroup = page->new_optgroup(L("Seam"), L"param_seam");
         optgroup->append_single_option_line("seam_position", "Seam");
         optgroup->append_single_option_line("seam_gap", "Seam");
+        optgroup->append_single_option_line("seam_slope_type");
+        optgroup->append_single_option_line("seam_slope_conditional");
+        optgroup->append_single_option_line("scarf_angle_threshold");
+        optgroup->append_single_option_line("seam_slope_start_height");
+        optgroup->append_single_option_line("seam_slope_entire_loop");
+        optgroup->append_single_option_line("seam_slope_min_length");
+        optgroup->append_single_option_line("seam_slope_steps");
+        optgroup->append_single_option_line("seam_slope_inner_walls");
         optgroup->append_single_option_line("wipe_speed", "Seam");
 
         optgroup = page->new_optgroup(L("Precision"), L"param_precision");