Fix scarf seams

src/libslic3r/ArcFitter.cpp

@@ -85,7 +85,7 @@ static void do_arc_fitting_tmpl(const POINTS& points, std::vector<PathFittingDat
             } else {
                 //BBS: save the first segment as line move when 3 point-line can't be fit as arc move
                 if (result.empty() || result.back().path_type != EMovePathType::Linear_move)
-                    result.emplace_back(std::move(PathFittingData{front_index, front_index + 1, EMovePathType::Linear_move, ArcSegment()}));
+                    result.emplace_back(PathFittingData{front_index, front_index + 1, EMovePathType::Linear_move, ArcSegment()});
                 else if(result.back().path_type == EMovePathType::Linear_move)
                     result.back().end_point_index = front_index + 1;
             }
@@ -98,7 +98,7 @@ static void do_arc_fitting_tmpl(const POINTS& points, std::vector<PathFittingDat
 	//BBS: handle the remain data
     if (front_index != back_index) {
         if (result.empty() || result.back().path_type != EMovePathType::Linear_move)
-            result.emplace_back(std::move(PathFittingData{front_index, back_index, EMovePathType::Linear_move, ArcSegment()}));
+            result.emplace_back(PathFittingData{front_index, back_index, EMovePathType::Linear_move, ArcSegment()});
         else if (result.back().path_type == EMovePathType::Linear_move)
             result.back().end_point_index = back_index;
     }

src/libslic3r/GCode.cpp

@@ -5541,7 +5541,11 @@ static std::unique_ptr<EdgeGrid::Grid> calculate_layer_edge_grid(const Layer& la
     return out;
 }
 
-std::string GCode::extrude_loop(const ExtrusionLoop &loop_ref, std::string description, double speed, const ExtrusionEntitiesPtr& region_perimeters, const Point* start_point)
+std::string GCode::extrude_loop(const ExtrusionLoop&        loop_ref,
+                                const std::string&          description,
+                                double                      speed,
+                                const ExtrusionEntitiesPtr& region_perimeters,
+                                const Point*                start_point)
 {
     // get a copy; don't modify the orientation of the original loop object otherwise
     // next copies (if any) would not detect the correct orientation
@@ -5707,7 +5711,7 @@ std::string GCode::extrude_loop(const ExtrusionLoop &loop_ref, std::string descr
     if (!enable_seam_slope) {
         for (ExtrusionPaths::iterator path = paths.begin(); path != paths.end(); ++path) {
             gcode += this->_extrude(*path, description, speed_for_path(*path));
-            // Orca: Adaptive PA - dont adapt PA after the first pultipath extrusion is completed
+            // Orca: Adaptive PA - dont adapt PA after the first multipath extrusion is completed
             // as we have already set the PA value to the average flow over the totality of the path
             // in the first extrude move
             // TODO: testing is needed with slope seams and adaptive PA.
@@ -5819,7 +5823,7 @@ std::string GCode::extrude_loop(const ExtrusionLoop &loop_ref, std::string descr
     return gcode;
 }
 
-std::string GCode::extrude_multi_path(const ExtrusionMultiPath &multipath, std::string description, double speed)
+std::string GCode::extrude_multi_path(const ExtrusionMultiPath& multipath, const std::string& description, double speed)
 {
     // extrude along the path
     std::string gcode;
@@ -5868,7 +5872,10 @@ std::string GCode::extrude_multi_path(const ExtrusionMultiPath &multipath, std::
     return gcode;
 }
 
-std::string GCode::extrude_entity(const ExtrusionEntity &entity, std::string description, double speed, const ExtrusionEntitiesPtr& region_perimeters)
+std::string GCode::extrude_entity(const ExtrusionEntity&      entity,
+                                  const std::string&          description,
+                                  double                      speed,
+                                  const ExtrusionEntitiesPtr& region_perimeters)
 {
     if (const ExtrusionPath* path = dynamic_cast<const ExtrusionPath*>(&entity))
         return this->extrude_path(*path, description, speed);
@@ -5881,7 +5888,7 @@ std::string GCode::extrude_entity(const ExtrusionEntity &entity, std::string des
     return "";
 }
 
-std::string GCode::extrude_path(const ExtrusionPath &path, std::string description, double speed)
+std::string GCode::extrude_path(const ExtrusionPath& path, const std::string& description, double speed)
 {
     // Orca: Reset average multipath flow as this is a single line, single extrude volumetric speed path
     m_multi_flow_segment_path_pa_set = false;
@@ -6155,12 +6162,7 @@ std::string GCode::_extrude(const ExtrusionPath &path, std::string description,
                 throw RuntimeError("GCode: very low z");
             }
         }
-        gcode += this->travel_to(
+        gcode += this->travel_to(path.first_point(), path.role(), "move to first " + description + " point", z);
-            path.first_point(),
-            path.role(),
-            "move to first " + description + " point; size " + std::to_string(path.polyline.size()),
-            z
-        );
         m_need_change_layer_lift_z = false;
         // Orca: ensure Z matches planned layer height
         if (_last_pos_undefined && !slope_need_z_travel) {

src/libslic3r/GCode.hpp

@@ -390,12 +390,19 @@ private:
     std::string     change_layer(coordf_t print_z);
     // Orca: pass the complete collection of region perimeters to the extrude loop to check whether the wipe before external loop
     // should be executed
-    std::string     extrude_entity(const ExtrusionEntity &entity, std::string description = "", double speed = -1., const ExtrusionEntitiesPtr& region_perimeters = ExtrusionEntitiesPtr());
+    std::string extrude_entity(const ExtrusionEntity&      entity,
+                               const std::string&          description       = "",
+                               double                      speed             = -1.,
+                               const ExtrusionEntitiesPtr& region_perimeters = ExtrusionEntitiesPtr());
     // Orca: pass the complete collection of region perimeters to the extrude loop to check whether the wipe before external loop
     // should be executed
-    std::string     extrude_loop(const ExtrusionLoop &loop, std::string description, double speed = -1., const ExtrusionEntitiesPtr& region_perimeters = ExtrusionEntitiesPtr(), const Point* start_point = nullptr);
+    std::string extrude_loop(const ExtrusionLoop&        loop,
-    std::string     extrude_multi_path(const ExtrusionMultiPath &multipath, std::string description = "", double speed = -1.);
+                             const std::string&          description,
-    std::string     extrude_path(const ExtrusionPath &path, std::string description = "", double speed = -1.);
+                             double                      speed             = -1.,
+                             const ExtrusionEntitiesPtr& region_perimeters = ExtrusionEntitiesPtr(),
+                             const Point*                start_point       = nullptr);
+    std::string extrude_multi_path(const ExtrusionMultiPath& multipath, const std::string& description = "", double speed = -1.);
+    std::string extrude_path(const ExtrusionPath& path, const std::string& description = "", double speed = -1.);
 
     // Orca: Adaptive PA variables
     // Used for adaptive PA when extruding paths with multiple, varying flow segments.

src/libslic3r/GCode/SeamPlacer.cpp

@@ -1514,8 +1514,7 @@ void SeamPlacer::place_seam(const Layer *layer, ExtrusionLoop &loop,
       current.path_idx = next_idx_modulo(current.path_idx, loop.paths.size());
       current.segment_idx = 0;
     }
-    const Point3 &p3 = loop.paths[current.path_idx].polyline.points[current.segment_idx];
+    current.foot_pt = loop.paths[current.path_idx].polyline.points[current.segment_idx].to_point();
-    current.foot_pt = Point(p3.x(), p3.y());
     return current;
   };
 
@@ -1528,8 +1527,7 @@ void SeamPlacer::place_seam(const Layer *layer, ExtrusionLoop &loop,
   size_t closest_perimeter_point_index = 0;
   { // local space for the closest_perimeter_point_index
     Perimeter *closest_perimeter = nullptr;
-    const Point3 &init_p3 = loop.paths[0].polyline.points[0];
+    ExtrusionLoop::ClosestPathPoint closest_point{0, 0, loop.paths[0].polyline.points[0].to_point()};
-    ExtrusionLoop::ClosestPathPoint closest_point{0,0,Point(init_p3.x(), init_p3.y())};
     size_t points_count = std::accumulate(loop.paths.begin(), loop.paths.end(), 0, [](size_t acc,const ExtrusionPath& p) {
       return acc + p.polyline.points.size();
     });

src/libslic3r/LayerRegion.cpp

@@ -3,6 +3,7 @@
 #include "ClipperUtils.hpp"
 #include "Geometry.hpp"
 #include "PerimeterGenerator.hpp"
+#include "Point.hpp"
 #include "Print.hpp"
 #include "Surface.hpp"
 #include "BoundingBox.hpp"

src/libslic3r/Line.hpp

@@ -236,6 +236,11 @@ public:
     // Convert to 2D line by dropping Z coordinate
     Line to_line() const { return Line(this->a.to_point(), this->b.to_point()); }
 
+    static inline double distance_to_squared(const Point3& point, const Point3& a, const Point3& b)
+    {
+        return line_alg::distance_to_squared(Line3{a, b}, Vec<3, coord_t>{point});
+    }
+
     Point3 a;
     Point3 b;
 

src/libslic3r/MultiPoint.cpp

@@ -422,32 +422,23 @@ Points MultiPoint::concave_hull_2d(const Points& pts, const double tolerence)
     return min_distance;
 }
 
-
+void MultiPoint3::translate(const Point3& v)
-void MultiPoint3::translate(double x, double y)
 {
-    for (Vec3crd &p : points) {
+    for (Point3& pt : points)
-        p(0) += coord_t(x);
+        pt += v;
-        p(1) += coord_t(y);
-    }
-}
-
-void MultiPoint3::translate(const Point& vector)
-{
-    this->translate(vector(0), vector(1));
 }
 
 double MultiPoint3::length() const
 {
-    double len = 0.0;
+    const Lines3& lines = this->lines();
-    for (const Line3& line : this->lines())
+    double        len   = 0;
-        len += line.length();
+    for (auto it = lines.cbegin(); it != lines.cend(); ++it) {
+        len += it->length();
+    }
     return len;
 }
 
-BoundingBox3 MultiPoint3::bounding_box() const
+BoundingBox3 MultiPoint3::bounding_box() const { return BoundingBox3(this->points); }
-{
-    return BoundingBox3(points);
-}
 
 bool MultiPoint3::remove_duplicate_points()
 {
@@ -472,48 +463,72 @@ bool MultiPoint3::remove_duplicate_points()
 }
 
 // Douglas-Peucker simplification for 3D points
-Points3 MultiPoint3::_douglas_peucker(const Points3 &points, double tolerance)
+Points3 MultiPoint3::_douglas_peucker(const Points3& pts, double tolerance)
 {
-    if (points.size() <= 2) return points;
+    Points3 result_pts;
-
+    double  tolerance_sq = tolerance * tolerance;
-    // Find the point with maximum distance from line segment
+    if (!pts.empty()) {
-    double max_dist = 0;
+        const Point3* anchor      = &pts.front();
-    size_t max_idx = 0;
+        size_t        anchor_idx  = 0;
-    const Point3 &first = points.front();
+        const Point3* floater     = &pts.back();
-    const Point3 &last = points.back();
+        size_t        floater_idx = pts.size() - 1;
-    Line3 line(first, last);
+        result_pts.reserve(pts.size());
-
+        result_pts.emplace_back(*anchor);
-    for (size_t i = 1; i < points.size() - 1; ++i) {
+        if (anchor_idx != floater_idx) {
-        // Calculate perpendicular distance to line segment
+            assert(pts.size() > 1);
-        Point3 proj = points[i].projection_onto(line);
+            std::vector<size_t> dpStack;
-        double dist = points[i].distance_to(proj);
+            dpStack.reserve(pts.size());
-        if (dist > max_dist) {
+            dpStack.emplace_back(floater_idx);
-            max_dist = dist;
+            for (;;) {
-            max_idx = i;
+                double max_dist_sq  = 0.0;
+                size_t furthest_idx = anchor_idx;
+                // find point furthest from line seg created by (anchor, floater) and note it
+                for (size_t i = anchor_idx + 1; i < floater_idx; ++i) {
+                    double dist_sq = Line3::distance_to_squared(pts[i], *anchor, *floater);
+                    if (dist_sq > max_dist_sq) {
+                        max_dist_sq  = dist_sq;
+                        furthest_idx = i;
                     }
                 }
-
+                // remove point if less than tolerance
-    // If max distance is greater than tolerance, recursively simplify
+                if (max_dist_sq <= tolerance_sq) {
-    if (max_dist > tolerance) {
+                    result_pts.emplace_back(*floater);
-        // Recursive call for first part
+                    anchor_idx = floater_idx;
-        Points3 left_points(points.begin(), points.begin() + max_idx + 1);
+                    anchor     = floater;
-        Points3 left_result = _douglas_peucker(left_points, tolerance);
+                    assert(dpStack.back() == floater_idx);
-
+                    dpStack.pop_back();
-        // Recursive call for second part
+                    if (dpStack.empty())
-        Points3 right_points(points.begin() + max_idx, points.end());
+                        break;
-        Points3 right_result = _douglas_peucker(right_points, tolerance);
+                    floater_idx = dpStack.back();
-
-        // Concatenate results (avoiding duplicate middle point)
-        Points3 result = left_result;
-        result.insert(result.end(), right_result.begin() + 1, right_result.end());
-        return result;
                 } else {
-        // All points between first and last can be removed
+                    floater_idx = furthest_idx;
-        Points3 result;
+                    dpStack.emplace_back(floater_idx);
-        result.push_back(first);
-        result.push_back(last);
-        return result;
                 }
+                floater = &pts[floater_idx];
+            }
+        }
+        assert(result_pts.front() == pts.front());
+        assert(result_pts.back() == pts.back());
+
+#if 0
+        {
+            static int iRun = 0;
+			BoundingBox bbox(pts);
+			BoundingBox bbox2(result_pts);
+			bbox.merge(bbox2);
+            SVG svg(debug_out_path("douglas_peucker_%d.svg", iRun ++).c_str(), bbox);
+            if (pts.front() == pts.back())
+                svg.draw(Polygon(pts), "black");
+            else
+                svg.draw(Polyline(pts), "black");
+            if (result_pts.front() == result_pts.back())
+                svg.draw(Polygon(result_pts), "green", scale_(0.1));
+            else
+                svg.draw(Polyline(result_pts), "green", scale_(0.1));
+        }
+#endif
+    }
+    return result_pts;
 }
 
 BoundingBox get_extents(const MultiPoint &mp)

src/libslic3r/MultiPoint.hpp

@@ -121,9 +121,13 @@ public:
 
     void append(const Point3& point) { this->points.push_back(point); }
     void append(const Vec3crd& point) { this->points.push_back(Point3(point)); }
+    void append(const Points3::const_iterator& begin, const Points3::const_iterator& end)
+    {
+        this->points.insert(this->points.end(), begin, end);
+    }
 
-    void translate(double x, double y);
+    void translate(double x, double y, double z = 0) { this->translate(Point3(coord_t(x), coord_t(y), coord_t(z))); }
-    void translate(const Point& vector);
+    void translate(const Point3& vector);
     void reverse() { std::reverse(this->points.begin(), this->points.end()); }
     void rotate(double angle) { this->rotate(cos(angle), sin(angle)); }
     void rotate(double cos_angle, double sin_angle);

src/libslic3r/PerimeterGenerator.cpp

@@ -464,10 +464,8 @@ static ExtrusionEntityCollection traverse_extrusions(const PerimeterGenerator& p
                     };
                     std::unordered_map<Point, PointInfo, PointHash> point_occurrence;
                     for (const ExtrusionPath& path : paths) {
-                        const Point3 &first_p3 = path.polyline.first_point();
+                        Point first_p = path.polyline.first_point().to_point();
-                        const Point3 &last_p3 = path.polyline.last_point();
+                        Point last_p  = path.polyline.last_point().to_point();
-                        Point first_p = Point(first_p3.x(), first_p3.y());
-                        Point last_p = Point(last_p3.x(), last_p3.y());
                         ++point_occurrence[first_p].occurrence;
                         ++point_occurrence[last_p].occurrence;
                         if (path.role() == erOverhangPerimeter) {
@@ -660,13 +658,17 @@ bool paths_touch(const ExtrusionPath &path_one, const ExtrusionPath &path_two, d
 {
     AABBTreeLines::LinesDistancer<Line> lines_two{path_two.as_polyline().lines()};
     for (size_t pt_idx = 0; pt_idx < path_one.polyline.size(); pt_idx++) {
-        const Point3 &p3 = path_one.polyline.points[pt_idx];
+        Point pt = path_one.polyline.points[pt_idx].to_point();
-        if (lines_two.distance_from_lines<false>(Point(p3.x(), p3.y())) < limit_distance) { return true; }
+        if (lines_two.distance_from_lines<false>(pt) < limit_distance) {
+            return true;
+        }
     }
     AABBTreeLines::LinesDistancer<Line> lines_one{path_one.as_polyline().lines()};
     for (size_t pt_idx = 0; pt_idx < path_two.polyline.size(); pt_idx++) {
-        const Point3 &p3 = path_two.polyline.points[pt_idx];
+        Point pt = path_two.polyline.points[pt_idx].to_point();
-        if (lines_one.distance_from_lines<false>(Point(p3.x(), p3.y())) < limit_distance) { return true; }
+        if (lines_one.distance_from_lines<false>(pt) < limit_distance) {
+            return true;
+        }
     }
     return false;
 }
@@ -1032,8 +1034,7 @@ std::tuple<std::vector<ExtrusionPaths>, Polygons> generate_extra_perimeters_over
                     size_t min_dist_idx = 0;
                     double min_dist = std::numeric_limits<double>::max();
                     for (size_t i = 0; i < overhang_region.front().polyline.size(); i++) {
-                        const Point3 &p3 = overhang_region.front().polyline.points[i];
+                        Point p = overhang_region.front().polyline.points[i].to_point();
-                        Point p = Point(p3.x(), p3.y());
                         if (double d = lower_layer_aabb_tree.distance_from_lines<true>(p) < min_dist) {
                             min_dist = d;
                             min_dist_idx = i;

src/libslic3r/Point.cpp

@@ -1,4 +1,5 @@
 #include "Point.hpp"
+#include "Exception.hpp"
 #include "Line.hpp"
 #include "MultiPoint.hpp"
 #include "Polyline.hpp"
@@ -266,11 +267,21 @@ Points to_points(const Points3 &points3) {
     Points points2;
     points2.reserve(points3.size());
     for (const Point3 &pt : points3) {
-        points2.push_back(pt.to_point());
+        points2.emplace_back(pt.to_point());
     }
     return points2;
 }
 
+Points3 to_points3(const Points& points)
+{
+    Points3 points3;
+    points3.reserve(points.size());
+    for (const Point& pt : points) {
+        points3.emplace_back(pt);
+    }
+    return points3;
+}
+
 // Point3 method implementations
 void Point3::rotate(double angle, const Point3 &center) {
     Vec3crd diff = *this - center;
@@ -311,6 +322,7 @@ double Point3::ccw_angle(const Point3 &p1, const Point3 &p2) const {
 Point3 Point3::projection_onto(const MultiPoint3 &poly) const {
     // TODO: Implement proper 3D projection when MultiPoint3 conversion methods are ready
     // For now, stub implementation
+    throw RuntimeError("Point3::projection_onto(MultiPoint3) not implemented yet");
     return *this;
 }
 

src/libslic3r/Point.hpp

@@ -62,7 +62,7 @@ using PointsAllocator = tbb::scalable_allocator<BaseType>;
 using Points         = std::vector<Point, PointsAllocator<Point>>;
 using PointPtrs      = std::vector<Point*>;
 using PointConstPtrs = std::vector<const Point*>;
-using Points3        = std::vector<Point3>;
+using Points3         = std::vector<Point3, PointsAllocator<Point3>>;
 using Pointfs        = std::vector<Vec2d>;
 using Vec2ds         = std::vector<Vec2d>;
 using Pointf3s       = std::vector<Vec3d>;
@@ -88,6 +88,7 @@ using Transform3d    = Eigen::Transform<double, 3, Eigen::Affine, Eigen::DontAli
 Polyline to_polyline(const Points &points);
 Polyline3 to_polyline(const Points3 &points);
 Points to_points(const Points3 &points);
+Points3   to_points3(const Points& points);
 
 // using ColorRGBA      = std::array<float, 4>;
 // I don't know why Eigen::Transform::Identity() return a const object...
@@ -422,6 +423,12 @@ inline Point lerp(const Point &a, const Point &b, double t)
     return ((1. - t) * a.cast<double>() + t * b.cast<double>()).cast<coord_t>();
 }
 
+inline Point3 lerp(const Point3& a, const Point3& b, double t)
+{
+    assert((t >= -EPSILON) && (t <= 1. + EPSILON));
+    return Point3(((1. - t) * a.cast<double>() + t * b.cast<double>()).cast<coord_t>());
+}
+
 // if IncludeBoundary, then a bounding box is defined even for a single point.
 // otherwise a bounding box is only defined if it has a positive area.
 template<bool IncludeBoundary = false>

src/libslic3r/Polyline.cpp

@@ -661,19 +661,17 @@ void ThickPolyline::start_at_index(int index)
 Lines3 Polyline3::lines() const
 {
     Lines3 lines;
-    if (points.size() >= 2)
+    if (this->points.size() >= 2) {
-    {
+        lines.reserve(this->points.size() - 1);
-        lines.reserve(points.size() - 1);
+        for (Points3::const_iterator it = this->points.begin(); it != this->points.end() - 1; ++it) {
-        for (Points3::const_iterator it = points.begin(); it != points.end() - 1; ++it)
-        {
             lines.emplace_back(*it, *(it + 1));
         }
     }
     return lines;
 }
 
-// Polyline3 ZAA methods implementation
+Polyline Polyline3::to_polyline() const
-Polyline Polyline3::to_polyline() const {
+{
     Polyline out;
     out.points.reserve(this->points.size());
     for (const Point3 &point : this->points) {
@@ -682,8 +680,10 @@ Polyline Polyline3::to_polyline() const {
     return out;
 }
 
-void Polyline3::clip_end(double distance) {
+void Polyline3::clip_end(double distance)
-    size_t remove_after_index = this->size();
+{
+    bool   last_point_inserted = false;
+    size_t remove_after_index  = MultiPoint3::size();
     while (distance > 0) {
         Vec3d last_point = this->last_point().cast<double>();
         this->points.pop_back();
@@ -695,32 +695,63 @@ void Polyline3::clip_end(double distance) {
         Vec3d  v    = this->last_point().cast<double>() - last_point;
         double lsqr = v.squaredNorm();
         if (lsqr > distance * distance) {
-            Vec3d result = last_point + v * (distance / sqrt(lsqr));
+            this->points.emplace_back((last_point + v * (distance / sqrt(lsqr))).cast<coord_t>());
-            this->points.emplace_back(Point3(coord_t(result.x()), coord_t(result.y()), coord_t(result.z())));
+            last_point_inserted = true;
             break;
         }
         distance -= sqrt(lsqr);
     }
 
-    // Clear fitting result if it's affected
+    // BBS: don't need to clip fitting result if it's empty
-    if (!fitting_result.empty()) {
+    if (fitting_result.empty())
+        return;
     while (!fitting_result.empty() && fitting_result.back().start_point_index >= remove_after_index)
         fitting_result.pop_back();
     if (!fitting_result.empty()) {
+        // BBS: last remaining segment is arc move, then clip the arc at last point
+        if (fitting_result.back().path_type == EMovePathType::Arc_move_ccw ||
+            fitting_result.back().path_type == EMovePathType::Arc_move_cw) {
+            if (fitting_result.back().arc_data.clip_end(this->last_point().to_point()))
+                // BBS: succeed to clip arc, then update the last point
+                // TODO: fix z parameter
+                this->points.back() = Point3(fitting_result.back().arc_data.end_point, this->points.back().z());
+            else
+                // BBS: Failed to clip arc, then back to linear move
+                fitting_result.back().path_type = EMovePathType::Linear_move;
+        }
         fitting_result.back().end_point_index = this->points.size() - 1;
     }
 }
-}
 
-void Polyline3::simplify(double tolerance) {
+void Polyline3::simplify(double tolerance)
+{
     this->points = MultiPoint3::_douglas_peucker(this->points, tolerance);
     this->fitting_result.clear();
 }
 
-void Polyline3::simplify_by_fitting_arc(double tolerance) {
+void Polyline3::simplify_by_fitting_arc(double tolerance)
-    // For now, just use regular simplify
+{
-    // Full ZAA implementation would use ArcFitter::do_arc_fitting_and_simplify
+    // BBS: do arc fit first, then use DP simplify to handle the straight part to reduce point.
-    this->simplify(tolerance);
+    Points points_2d = to_points(this->points);
+    ArcFitter::do_arc_fitting_and_simplify(points_2d, this->fitting_result, tolerance);
+    this->points = to_points3(points_2d);
+}
+
+void Polyline3::reverse()
+{
+    // BBS: reverse points
+    MultiPoint3::reverse();
+    // BBS: reverse the fitting_result
+    if (!this->fitting_result.empty()) {
+        for (size_t i = 0; i < this->fitting_result.size(); i++) {
+            std::swap(fitting_result[i].start_point_index, fitting_result[i].end_point_index);
+            fitting_result[i].start_point_index = MultiPoint3::size() - 1 - fitting_result[i].start_point_index;
+            fitting_result[i].end_point_index   = MultiPoint3::size() - 1 - fitting_result[i].end_point_index;
+            if (fitting_result[i].is_arc_move())
+                fitting_result[i].reverse_arc_path();
+        }
+        std::reverse(this->fitting_result.begin(), this->fitting_result.end());
+    }
 }
 
 bool Polyline3::split_at_index(const size_t index, Polyline3 *p1, Polyline3 *p2) const
@@ -737,7 +768,7 @@ bool Polyline3::split_at_index(const size_t index, Polyline3 *p1, Polyline3 *p2)
         p2->append(this->last_point());
         *p1 = *this;
     } else {
-        // Split first part
+        // BBS: spilit first part
         p1->clear();
         p1->points.reserve(index + 1);
         p1->points.insert(p1->begin(), this->begin(), this->begin() + index + 1);
@@ -745,7 +776,6 @@ bool Polyline3::split_at_index(const size_t index, Polyline3 *p1, Polyline3 *p2)
         if (this->split_fitting_result_before_index(index, new_endpoint, p1->fitting_result))
             p1->points.back() = new_endpoint;
 
-        // Split second part
         p2->clear();
         p2->points.reserve(this->size() - index);
         p2->points.insert(p2->begin(), this->begin() + index, this->end());
@@ -756,58 +786,74 @@ bool Polyline3::split_at_index(const size_t index, Polyline3 *p1, Polyline3 *p2)
     return true;
 }
 
-void Polyline3::append(const Point3& point) {
+void Polyline3::append(const Point3& point)
-    // Don't append if same as last point
+{
+    // // Don't append if same as last point
+    // if (!this->empty() && this->last_point() == point)
+    //     return;
+
+    // this->points.push_back(point);
+    // append_fitting_result_after_append_points();
+
+    // BBS: don't need to append same point
     if (!this->empty() && this->last_point() == point)
         return;
-
+    MultiPoint3::append(point);
-    this->points.push_back(point);
+    append_fitting_result_after_append_points();
-    // Clear fitting result as structure changed
-    this->fitting_result.clear();
 }
 
-void Polyline3::append(const Polyline3 &src) {
+void Polyline3::append(const Polyline3& src)
+{
     if (!src.is_valid()) return;
 
     if (this->points.empty()) {
         this->points = src.points;
         this->fitting_result = src.fitting_result;
     } else {
-        // Append points
+        // BBS: append the first point to create connection first, update the fitting date as well
-        if (!src.points.empty() && !this->points.empty() && this->last_point() == src.points.front()) {
+        this->append(src.points[0]);
-            // Skip first point if it's the same as our last point
+        // BBS: append a polyline which has fitting data to a polyline without fitting data.
-            this->points.insert(this->points.end(), src.points.begin() + 1, src.points.end());
+        // Then create a fake fitting data first, so that we can keep the fitting data in last polyline
-        } else {
+        if (this->fitting_result.empty() && !src.fitting_result.empty()) {
-            this->points.insert(this->points.end(), src.points.begin(), src.points.end());
+            this->fitting_result.emplace_back(PathFittingData{0, this->points.size() - 1, EMovePathType::Linear_move, ArcSegment()});
         }
-        // Note: Full arc fitting integration would merge fitting_result here
+        // BBS: then append the remain points
-        this->fitting_result.clear();
+        MultiPoint3::append(src.points.begin() + 1, src.points.end());
+        // BBS: finally append the fitting data
+        append_fitting_result_after_append_polyline(src);
     }
 }
 
-void Polyline3::append_before(const Point3& point) {
+void Polyline3::append_before(const Point3& point)
-    // Don't append if same as first point
+{
+    // BBS: don't need to append same point
     if (!this->empty() && this->first_point() == point)
         return;
-
+    if (this->size() == 1) {
-    this->points.insert(this->points.begin(), point);
-    // Clear fitting result as structure changed
         this->fitting_result.clear();
+        MultiPoint3::append(point);
+        MultiPoint3::reverse();
+    } else {
+        this->reverse();
+        this->append(point);
+        this->reverse();
+    }
 }
 
-void Polyline3::split_at(Point &point, Polyline3* p1, Polyline3* p2) const {
+void Polyline3::split_at(Point& point, Polyline3* p1, Polyline3* p2) const
+{
     if (this->points.empty()) return;
 
-    // Check if the point is on the polyline
+    // 0 judge whether the point is on the polyline
     int index = this->find_point(point);
     if (index != -1) {
-        // The split point is on the polyline
+        // BBS: the spilit point is on the polyline, then easy
         split_at_index(index, p1, p2);
         point = p1->is_valid() ? p1->last_point().to_point() : p2->first_point().to_point();
         return;
     }
 
-    // Find the line to split at
+    // 1 find the line to split at
     size_t line_idx = 0;
     Point p = this->first_point().to_point();
     double min = (p - point).cast<double>().norm();
@@ -821,7 +867,8 @@ void Polyline3::split_at(Point &point, Polyline3* p1, Polyline3* p2) const {
         }
     }
 
-    // Judge whether the closest point is one vertex of polyline
+    // 2 judge whether the cloest point is one vertex of polyline.
+    //   and spilit the polyline at different index
     index = this->find_point(p);
     if (index != -1) {
         this->split_at_index(index, p1, p2);
@@ -834,7 +881,6 @@ void Polyline3::split_at(Point &point, Polyline3* p1, Polyline3* p2) const {
         this->split_at_index(line_idx + 1, &temp, p2);
         p2->append_before(Point3(point, p2->first_point().z()));
     }
-    point = p;
 }
 
 void Polyline3::split_at(Point3 &point, Polyline3* p1, Polyline3* p2) const {
@@ -845,46 +891,153 @@ void Polyline3::split_at(Point3 &point, Polyline3* p1, Polyline3* p2) const {
 
 bool Polyline3::split_at_length(const double length, Polyline3 *p1, Polyline3 *p2) const {
     if (this->points.empty()) return false;
-    if (length < 0 || length > this->length()) { return false; }
+    if (length < 0 || length > this->length()) {
+        return false;
+    }
 
     if (length < SCALED_EPSILON) {
         p1->clear();
-        p1->append_before(this->first_point());
+        p1->append(this->first_point());
         *p2 = *this;
     } else if (is_approx(length, this->length(), SCALED_EPSILON)) {
         p2->clear();
-        p2->append_before(this->last_point());
+        p2->append(this->last_point());
         *p1 = *this;
     } else {
-        // Find the line to split at
+        // 1 find the line to split at
         size_t line_idx = 0;
         double acc_length = 0;
-        Point p = this->first_point().to_point();
+        Point3 p          = this->first_point();
         for (const auto& l : this->lines()) {
-            p = l.b.to_point();
+            p = l.b;
 
             const double current_length = l.length();
             if (acc_length + current_length >= length) {
-                p = lerp(l.a.to_point(), l.b.to_point(), (length - acc_length) / current_length);
+                p = lerp(l.a, l.b, (length - acc_length) / current_length);
                 break;
             }
             acc_length += current_length;
             line_idx++;
         }
 
-        // Judge whether the closest point is one vertex of polyline
+        // 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 {
             Polyline3 temp;
             this->split_at_index(line_idx, p1, &temp);
-            p1->append_before(Point3(p, p1->last_point().z()));
+            p1->append(p);
             this->split_at_index(line_idx + 1, &temp, p2);
-            p2->append_before(Point3(p, p2->first_point().z()));
+            p2->append_before(p);
         }
     }
     return true;
 }
 
+bool Polyline3::split_fitting_result_before_index(size_t index, Point3& new_endpoint, std::vector<PathFittingData>& data) const
+{
+    data.clear();
+    new_endpoint = this->points[index];
+    if (!this->fitting_result.empty()) {
+        // BBS: max size
+        data.reserve(this->fitting_result.size());
+        // BBS: save fitting result before index
+        for (size_t i = 0; i < this->fitting_result.size(); i++) {
+            if (this->fitting_result[i].start_point_index < index)
+                data.push_back(this->fitting_result[i]);
+            else
+                break;
+        }
+
+        if (!data.empty()) {
+            // BBS: need to clip the arc and generate new end point
+            if (data.back().is_arc_move() && data.back().end_point_index > index) {
+                if (!data.back().arc_data.clip_end(this->points[index].to_point()))
+                    // BBS: failed to clip arc, then return to be linear move
+                    data.back().path_type = EMovePathType::Linear_move;
+                else
+                    // BBS: succeed to clip arc, then update and return the new end point
+                    new_endpoint = Point3(data.back().arc_data.end_point, 0);
+            }
+            data.back().end_point_index = index;
+        }
+        data.shrink_to_fit();
+        return true;
+    }
+    return false;
+}
+
+bool Polyline3::split_fitting_result_after_index(size_t index, Point3& new_startpoint, std::vector<PathFittingData>& data) const
+{
+    data.clear();
+    new_startpoint = this->points[index];
+    if (!this->fitting_result.empty()) {
+        data.reserve(this->fitting_result.size());
+        for (size_t i = 0; i < this->fitting_result.size(); i++) {
+            if (this->fitting_result[i].end_point_index > index)
+                data.push_back(this->fitting_result[i]);
+        }
+        if (!data.empty()) {
+            for (size_t i = 0; i < data.size(); i++) {
+                if (i != 0) {
+                    data[i].start_point_index -= index;
+                    data[i].end_point_index -= index;
+                } else {
+                    data[i].end_point_index -= index;
+                    // BBS: need to clip the arc and generate new start point
+                    if (data.front().is_arc_move() && data.front().start_point_index < index) {
+                        if (!data.front().arc_data.clip_start(this->points[index].to_point()))
+                            // BBS: failed to clip arc, then return to be linear move
+                            data.front().path_type = EMovePathType::Linear_move;
+                        else
+                            // BBS: succeed to clip arc, then update and return the new start point
+                            new_startpoint = Point3(data.front().arc_data.start_point, 0);
+                    }
+                    data[i].start_point_index = 0;
+                }
+            }
+        }
+        data.shrink_to_fit();
+        return true;
+    }
+    return false;
+}
+
+void Polyline3::append_fitting_result_after_append_points()
+{
+    if (!fitting_result.empty()) {
+        if (fitting_result.back().is_linear_move()) {
+            fitting_result.back().end_point_index = this->points.size() - 1;
+        } else {
+            size_t new_start = fitting_result.back().end_point_index;
+            size_t new_end   = this->points.size() - 1;
+            if (new_start != new_end)
+                fitting_result.emplace_back(PathFittingData{new_start, new_end, EMovePathType::Linear_move, ArcSegment()});
+        }
+    }
+}
+
+void Polyline3::append_fitting_result_after_append_polyline(const Polyline3& src)
+{
+    if (!this->fitting_result.empty()) {
+        // BBS: offset and save the fitting_result from src polyline
+        if (!src.fitting_result.empty()) {
+            size_t old_size     = this->fitting_result.size();
+            size_t index_offset = this->fitting_result.back().end_point_index;
+            this->fitting_result.insert(this->fitting_result.end(), src.fitting_result.begin(), src.fitting_result.end());
+            for (size_t i = old_size; i < this->fitting_result.size(); i++) {
+                this->fitting_result[i].start_point_index += index_offset;
+                this->fitting_result[i].end_point_index += index_offset;
+            }
+        } else {
+            // BBS: the append polyline has no fitting data, then append as linear move directly
+            size_t new_start = this->fitting_result.back().end_point_index;
+            size_t new_end   = this->size() - 1;
+            if (new_start != new_end)
+                this->fitting_result.emplace_back(PathFittingData{new_start, new_end, EMovePathType::Linear_move, ArcSegment()});
+        }
+    }
+}
 }

src/libslic3r/Polyline.hpp

@@ -315,7 +315,7 @@ public:
     void simplify_by_fitting_arc(double tolerance);
 
     // Reverse the polyline
-    using MultiPoint3::reverse;
+    void reverse();
 
     // Split polyline at given index
     bool split_at_index(const size_t index, Polyline3 *p1, Polyline3 *p2) const;
@@ -344,15 +344,10 @@ public:
     std::vector<PathFittingData> fitting_result;
 
 private:
-    // Helper methods for split_at_index
+    void append_fitting_result_after_append_points();
-    bool split_fitting_result_before_index(size_t index, Point3 &new_endpoint, std::vector<PathFittingData> &result) const {
+    void append_fitting_result_after_append_polyline(const Polyline3& src);
-        // Simplified stub - full implementation would handle arc fitting data
+    bool split_fitting_result_before_index(size_t index, Point3& new_endpoint, std::vector<PathFittingData>& result) const;
-        return false;
+    bool split_fitting_result_after_index(size_t index, Point3& new_startpoint, std::vector<PathFittingData>& result) const;
-    }
-    bool split_fitting_result_after_index(size_t index, Point3 &new_startpoint, std::vector<PathFittingData> &result) const {
-        // Simplified stub - full implementation would handle arc fitting data
-        return false;
-    }
 };
 
 typedef std::vector<Polyline3> Polylines3;