From 2ce0d3a94643803fed89f82f8798871195562a3b Mon Sep 17 00:00:00 2001
From: supermerill <merill@fr.fr>
Date: Fri, 4 Jan 2019 19:08:18 +0100
Subject: [PATCH] Medial axis: taper the end of thin walls

---
 src/libslic3r/MedialAxis.cpp | 41 ++++++++++++++++++++++++++++++------
 src/libslic3r/MedialAxis.hpp |  1 +
 2 files changed, 35 insertions(+), 7 deletions(-)

diff --git a/src/libslic3r/MedialAxis.cpp b/src/libslic3r/MedialAxis.cpp
index c869ef36a..c4ddd1399 100644
--- a/src/libslic3r/MedialAxis.cpp
+++ b/src/libslic3r/MedialAxis.cpp
@@ -1283,7 +1283,6 @@ MedialAxis::ensure_not_overextrude(ThickPolylines& pp)
         for (ThickPolyline& polyline : pp) {
             for (coordf_t &width : polyline.width) {
                 width *= reduce_by;
-                width *= reduce_by;
             }
         }
     }
@@ -1333,8 +1332,7 @@ MedialAxis::simplify_polygon_frontier()
 }
 
 void
-MedialAxis::build(ThickPolylines* polylines_out)
-{
+MedialAxis::build(ThickPolylines* polylines_out) {
     this->id++;
     //std::cout << layerid << "\n";
     //{
@@ -1361,7 +1359,7 @@ MedialAxis::build(ThickPolylines* polylines_out)
     // compute the Voronoi diagram and extract medial axis polylines
     ThickPolylines pp;
     this->polyline_from_voronoi(this->expolygon.lines(), &pp);
-    
+
     concatThickPolylines(pp);
 
     //std::cout << "concatThickPolylines\n";
@@ -1374,8 +1372,8 @@ MedialAxis::build(ThickPolylines* polylines_out)
     //    svg.draw(pp);
     //    svg.Close();
     //}
-    
-    /* Find the maximum width returned; we're going to use this for validating and 
+
+    /* Find the maximum width returned; we're going to use this for validating and
        filtering the output segments. */
     double max_w = 0;
     for (ThickPolylines::const_iterator it = pp.begin(); it != pp.end(); ++it)
@@ -1488,8 +1486,10 @@ MedialAxis::build(ThickPolylines* polylines_out)
     //    svg.draw(pp);
     //    svg.Close();
     //}
-    if (nozzle_diameter != min_width)
+    if (nozzle_diameter != min_width) {
         grow_to_nozzle_diameter(pp, diff_ex(this->bounds, this->expolygon));
+        taper_ends(pp);
+    }
 
     polylines_out->insert(polylines_out->end(), pp.begin(), pp.end());
 
@@ -1513,6 +1513,33 @@ MedialAxis::grow_to_nozzle_diameter(ThickPolylines& pp, const ExPolygons& anchor
     }
 }
 
+void
+MedialAxis::taper_ends(ThickPolylines& pp) {
+    //ensure the width is not lower than 0.4.
+    for (ThickPolyline& polyline : pp) {
+        if (polyline.length() < nozzle_diameter * 2) continue;
+        if (polyline.endpoints.first) {
+            polyline.width[0] = min_width;
+            coord_t current_dist = min_width;
+            for (size_t i = 1; i<polyline.width.size(); ++i) {
+                current_dist += polyline.points[i - 1].distance_to(polyline.points[i]);
+                if (current_dist > polyline.width[i]) break;
+                polyline.width[i] = current_dist;
+            }
+        }
+        if (polyline.endpoints.second) {
+            size_t last_idx = polyline.width.size() - 1;
+            polyline.width[last_idx] = min_width;
+            coord_t current_dist = min_width;
+            for (size_t i = 1; i<polyline.width.size(); ++i) {
+                current_dist += polyline.points[last_idx - i + 1].distance_to(polyline.points[last_idx - i]);
+                if (current_dist > polyline.width[last_idx - i]) break;
+                polyline.width[last_idx - i] = current_dist;
+            }
+        }
+    }
+}
+
 ExtrusionEntityCollection thin_variable_width(const ThickPolylines &polylines, ExtrusionRole role, Flow flow) {
     // this value determines granularity of adaptive width, as G-code does not allow
     // variable extrusion within a single move; this value shall only affect the amount
diff --git a/src/libslic3r/MedialAxis.hpp b/src/libslic3r/MedialAxis.hpp
index 85607b718..9d71207b1 100644
--- a/src/libslic3r/MedialAxis.hpp
+++ b/src/libslic3r/MedialAxis.hpp
@@ -63,6 +63,7 @@ namespace Slic3r {
         void remove_too_short_polylines(ThickPolylines& pp, const coord_t min_size);
         void ensure_not_overextrude(ThickPolylines& pp);
         void grow_to_nozzle_diameter(ThickPolylines& pp, const ExPolygons& anchors);
+        void taper_ends(ThickPolylines& pp);
     };
 
     ExtrusionEntityCollection thin_variable_width(const ThickPolylines &polylines, ExtrusionRole role, Flow flow);