Fixed crash in Adaptive Cubic infill if just a single line was extracted.

New function to chain lines, however not used by the Adaptive Cubic infill.

src/libslic3r/Fill/FillAdaptive.cpp

@@ -361,8 +361,8 @@ static bool verify_traversal_order(
         c[1] - c[0], c[2] - c[0], c[3] - c[1], c[3] - c[2], c[3] - c[0],
         c[5] - c[4], c[6] - c[4], c[7] - c[5], c[7] - c[6], c[7] - c[4]
     };
-    assert(std::abs(dirs[4].z()) < 0.001);
+    assert(std::abs(dirs[4].z()) < 0.005);
-    assert(std::abs(dirs[9].z()) < 0.001);
+    assert(std::abs(dirs[9].z()) < 0.005);
     assert(dirs[0].isApprox(dirs[3]));
     assert(dirs[1].isApprox(dirs[2]));
     assert(dirs[5].isApprox(dirs[8]));
@@ -413,7 +413,7 @@ static void generate_infill_lines_recursive(
         Line  new_line(Point::new_scale(from), Point::new_scale(to));
         if (last_line.a.x() == std::numeric_limits<coord_t>::max()) {
             last_line.a = new_line.a;
-        } else if ((new_line.a - last_line.b).cwiseAbs().maxCoeff() > 300) { // SCALED_EPSILON is 100 and it is not enough) {
+        } else if ((new_line.a - last_line.b).cwiseAbs().maxCoeff() > 300) { // SCALED_EPSILON is 100 and it is not enough
             context.output_lines.emplace_back(last_line);
             last_line.a = new_line.a;
         }
@@ -434,64 +434,6 @@ static void generate_infill_lines_recursive(
     }
 }
 
-#if 0
-// Collect the line segments.
-static Polylines chain_lines(const std::vector<Line> &lines, const double point_distance_epsilon)
-{
-    // Create line end point lookup.
-    struct LineEnd {
-        LineEnd(Line *line, bool start) : line(line), start(start) {}
-        Line            *line;
-        // Is it the start or end point?
-        bool             start;
-        const Point&     point() const { return start ? line->a : line->b; }
-        const Point&     other_point() const { return start ? line->b : line->a; }
-        LineEnd          other_end() const { return LineEnd(line, ! start); }
-        bool operator==(const LineEnd &rhs) const { return this->line == rhs.line && this->start == rhs.start; }
-    };
-    struct LineEndAccessor {
-        const Point* operator()(const LineEnd &pt) const { return &pt.point(); }
-    };
-    typedef ClosestPointInRadiusLookup<LineEnd, LineEndAccessor> ClosestPointLookupType;
-    ClosestPointLookupType closest_end_point_lookup(point_distance_epsilon);
-    for (const Line &line : lines) {
-        closest_end_point_lookup.insert(LineEnd(&line, true));
-        closest_end_point_lookup.insert(LineEnd(&line, false));
-    }
-
-    // Chain the lines.
-    std::vector<char> line_consumed(lines.size(), false);
-    static const double point_distance_epsilon2 = point_distance_epsilon * point_distance_epsilon;
-    Polylines out;
-    for (const Line &seed : lines)
-        if (! line_consumed[&seed - lines.data()]) {
-            line_consumed[&seed - lines.data()] = true;
-            closest_end_point_lookup.erase(LineEnd(&seed, false));
-            closest_end_point_lookup.erase(LineEnd(&seed, true));
-            Polyline pl { seed.a, seed.b };
-            for (size_t round = 0; round < 2; ++ round) {
-                for (;;) {
-                    auto [line_end, dist2] = closest_end_point_lookup.find(pl.last_point());
-                    if (line_end == nullptr || dist2 >= point_distance_epsilon2)
-                        // Cannot extent in this direction.
-                        break;
-                    // Average the last point.
-                    pl.points.back() = 0.5 * (pl.points.back() + line_end->point());
-                    // and extend with the new line segment.
-                    pl.points.emplace_back(line_end->other_point());
-                    closest_end_point_lookup.erase(line_end);
-                    closest_end_point_lookup.erase(line_end->other_end());
-                    line_consumed[line_end->line - lines.data()] = true;
-                }
-                // reverse and try the oter direction.
-                pl.reverse();
-            }
-            out.emplace_back(std::move(pl));
-        }
-    return out;
-}
-#endif
-
 #ifndef NDEBUG
 //    #define ADAPTIVE_CUBIC_INFILL_DEBUG_OUTPUT
 #endif
@@ -574,10 +516,14 @@ void Filler::_fill_surface_single(
                 if (line.a.x() != std::numeric_limits<coord_t>::max())
                     lines.emplace_back(line);
         }
+#if 0
+        // Chain touching line segments, convert lines to polylines.
+        //all_polylines = chain_lines(lines, 300.); // SCALED_EPSILON is 100 and it is not enough
+#else
         // Convert lines to polylines.
-        //FIXME chain the lines
         all_polylines.reserve(lines.size());
         std::transform(lines.begin(), lines.end(), std::back_inserter(all_polylines), [](const Line& l) { return Polyline{ l.a, l.b }; });
+#endif
     }
 
     // Crop all polylines
@@ -590,7 +536,7 @@ void Filler::_fill_surface_single(
     }
 #endif /* ADAPTIVE_CUBIC_INFILL_DEBUG_OUTPUT */
 
-    if (params.dont_connect)
+    if (params.dont_connect || all_polylines.size() <= 1)
         append(polylines_out, std::move(all_polylines));
     else
         connect_infill(chain_polylines(std::move(all_polylines)), expolygon, polylines_out, this->spacing, params);

src/libslic3r/ShortestPath.cpp

@@ -1973,4 +1973,59 @@ std::vector<const PrintInstance*> chain_print_object_instances(const Print &prin
 	return out;
 }
 
+Polylines chain_lines(const std::vector<Line> &lines, const double point_distance_epsilon)
+{
+    // Create line end point lookup.
+    struct LineEnd {
+        LineEnd(const Line *line, bool start) : line(line), start(start) {}
+        const Line      *line;
+        // Is it the start or end point?
+        bool             start;
+        const Point&     point() const { return start ? line->a : line->b; }
+        const Point&     other_point() const { return start ? line->b : line->a; }
+        LineEnd          other_end() const { return LineEnd(line, ! start); }
+        bool operator==(const LineEnd &rhs) const { return this->line == rhs.line && this->start == rhs.start; }
+    };
+    struct LineEndAccessor {
+        const Point* operator()(const LineEnd &pt) const { return &pt.point(); }
+    };
+    typedef ClosestPointInRadiusLookup<LineEnd, LineEndAccessor> ClosestPointLookupType;
+    ClosestPointLookupType closest_end_point_lookup(point_distance_epsilon);
+    for (const Line &line : lines) {
+        closest_end_point_lookup.insert(LineEnd(&line, true));
+        closest_end_point_lookup.insert(LineEnd(&line, false));
+    }
+
+    // Chain the lines.
+    std::vector<char> line_consumed(lines.size(), false);
+    static const double point_distance_epsilon2 = point_distance_epsilon * point_distance_epsilon;
+    Polylines out;
+    for (const Line &seed : lines)
+        if (! line_consumed[&seed - lines.data()]) {
+            line_consumed[&seed - lines.data()] = true;
+            closest_end_point_lookup.erase(LineEnd(&seed, false));
+            closest_end_point_lookup.erase(LineEnd(&seed, true));
+            Polyline pl { seed.a, seed.b };
+            for (size_t round = 0; round < 2; ++ round) {
+                for (;;) {
+                    auto [line_end, dist2] = closest_end_point_lookup.find(pl.last_point());
+                    if (line_end == nullptr || dist2 >= point_distance_epsilon2)
+                        // Cannot extent in this direction.
+                        break;
+                    // Average the last point.
+                    pl.points.back() = (0.5 * (pl.points.back().cast<double>() + line_end->point().cast<double>())).cast<coord_t>();
+                    // and extend with the new line segment.
+                    pl.points.emplace_back(line_end->other_point());
+                    closest_end_point_lookup.erase(*line_end);
+                    closest_end_point_lookup.erase(line_end->other_end());
+                    line_consumed[line_end->line - lines.data()] = true;
+                }
+                // reverse and try the oter direction.
+                pl.reverse();
+            }
+            out.emplace_back(std::move(pl));
+        }
+    return out;
+}
+
 } // namespace Slic3r

src/libslic3r/ShortestPath.hpp

@@ -33,6 +33,8 @@ class Print;
 struct PrintInstance;
 std::vector<const PrintInstance*> 	 chain_print_object_instances(const Print &print);
 
+// Chain lines into polylines.
+Polylines 							 chain_lines(const std::vector<Line> &lines, const double point_distance_epsilon);
 
 } // namespace Slic3r