From 08402abf2bcc4ebbb8097f339580a2a862f2797d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Luk=C3=A1=C5=A1=20Hejl?= <hejl.lukas@gmail.com>
Date: Tue, 14 Dec 2021 14:48:25 +0100
Subject: Used double instead of float for computing distance between two
 polygon vertices in precompute_polygon_distances() in the avoid crossing
 perimeters.

Using a float instead of a double caused accumulation of error in the calculated distance, which in rare cases triggered an assert in get_shortest_direction().
---
 src/libslic3r/GCode/AvoidCrossingPerimeters.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/libslic3r/GCode/AvoidCrossingPerimeters.cpp b/src/libslic3r/GCode/AvoidCrossingPerimeters.cpp
index d29f7216a..48b9515f7 100644
--- a/src/libslic3r/GCode/AvoidCrossingPerimeters.cpp
+++ b/src/libslic3r/GCode/AvoidCrossingPerimeters.cpp
@@ -765,8 +765,8 @@ static void precompute_polygon_distances(const Polygon &polygon, std::vector<flo
 {
     polygon_distances_out.assign(polygon.size() + 1, 0.f);
     for (size_t point_idx = 1; point_idx < polygon.size(); ++point_idx)
-        polygon_distances_out[point_idx] = polygon_distances_out[point_idx - 1] + (polygon[point_idx].cast<float>() - polygon[point_idx - 1].cast<float>()).norm();
-    polygon_distances_out.back() = polygon_distances_out[polygon.size() - 1] + (polygon.points.back().cast<float>() - polygon.points.front().cast<float>()).norm();
+        polygon_distances_out[point_idx] = polygon_distances_out[point_idx - 1] + float((polygon[point_idx] - polygon[point_idx - 1]).cast<double>().norm());
+    polygon_distances_out.back() = polygon_distances_out[polygon.size() - 1] + float((polygon.points.back() - polygon.points.front()).cast<double>().norm());
 }
 
 static void precompute_expolygon_distances(const ExPolygon &ex_polygon, std::vector<std::vector<float>> &expolygon_distances_out)
-- 
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