From ff880ac3483f6600dfa70fca5fa1859a2f419460 Mon Sep 17 00:00:00 2001
From: remi durand <remi-j.durand@thalesgroup.com>
Date: Sat, 31 Jul 2021 19:43:42 +0200
Subject: [PATCH] Fix thin_wall detection supermerill/SuperSlicer#1437

---
 src/libslic3r/ClipperUtils.cpp | 4 ++--
 src/libslic3r/MedialAxis.cpp   | 5 ++++-
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/libslic3r/ClipperUtils.cpp b/src/libslic3r/ClipperUtils.cpp
index 5b47e7a98..db5dd463c 100644
--- a/src/libslic3r/ClipperUtils.cpp
+++ b/src/libslic3r/ClipperUtils.cpp
@@ -532,8 +532,8 @@ bool test_path(const ClipperLib::Path &path) {
     ClipperLib::IntPoint centroid = ClipperLib::Centroid(path, area);
     for (const ClipperLib::IntPoint& pt : path) {
         // &0x3FFFFFFF to let  (dx * dx + dy * dy) be storable into a int64
-        ClipperLib::cInt dx = (pt.X - centroid.X) & 0x3FFFFFFF;
-        ClipperLib::cInt dy = (pt.Y - centroid.Y) & 0x3FFFFFFF;
+        ClipperLib::cInt dx = std::abs(pt.X - centroid.X) & 0x3FFFFFFF;
+        ClipperLib::cInt dy = std::abs(pt.Y - centroid.Y) & 0x3FFFFFFF;
         ClipperLib::cInt dist_sqrd = (dx * dx + dy * dy);
         max_dist_sqrd = std::max(max_dist_sqrd, dist_sqrd);
     }
diff --git a/src/libslic3r/MedialAxis.cpp b/src/libslic3r/MedialAxis.cpp
index 66deb155f..9c2c9a21f 100644
--- a/src/libslic3r/MedialAxis.cpp
+++ b/src/libslic3r/MedialAxis.cpp
@@ -1606,6 +1606,8 @@ check_circular(ExPolygon& expolygon, coord_t max_variation) {
 void
 MedialAxis::build(ThickPolylines &polylines_out)
 {
+    //static int id = 0;
+    //id++;
     //std::cout << this->id << "\n";
     //{
     //    std::stringstream stri;
@@ -1629,11 +1631,12 @@ MedialAxis::build(ThickPolylines &polylines_out)
 
     //check for circular shape
     double radius = check_circular(this->expolygon, this->min_width/4);
-    if (radius > 0) {
+    if (radius > 0 && this->expolygon.contour.points.size() > 4) {
         ExPolygons miniPeri = offset_ex(this->expolygon.contour, -radius / 2);
         if (miniPeri.size() == 1 && miniPeri[0].holes.size() == 0) {
             ThickPolyline thickPoly;
             thickPoly.points = miniPeri[0].contour.points;
+            thickPoly.points.push_back(thickPoly.points.front());
             thickPoly.endpoints.first = false;
             thickPoly.endpoints.second = false;
             for (int i = 0; i < thickPoly.points.size(); i++) {