From 14417bf176d0a8143da4cc3739daee9c506112b0 Mon Sep 17 00:00:00 2001
From: "salt.wei" <salt.wei@bambulab.com>
Date: Tue, 6 Dec 2022 15:52:24 +0800
Subject: [PATCH] ENH: optimize bridge detect to choose short direction

For some corner case, the bridge detect may choose the long
distance rathan than the short distance.

Calculate the percentage of archored lines and choose
the shortest length

Signed-off-by: salt.wei <salt.wei@bambulab.com>
Change-Id: Ia74842f3135681373f649a014c270a1b9d1755e7
---
 src/libslic3r/BridgeDetector.cpp | 9 +++++++--
 src/libslic3r/BridgeDetector.hpp | 5 +++--
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/src/libslic3r/BridgeDetector.cpp b/src/libslic3r/BridgeDetector.cpp
index 03d671db4..a60f45f11 100644
--- a/src/libslic3r/BridgeDetector.cpp
+++ b/src/libslic3r/BridgeDetector.cpp
@@ -122,6 +122,7 @@ bool BridgeDetector::detect_angle(double bridge_direction_override)
         double max_length = 0;
         {
             Lines clipped_lines = intersection_ln(lines, clip_area);
+            size_t archored_line_num = 0;
             for (size_t i = 0; i < clipped_lines.size(); ++i) {
                 const Line &line = clipped_lines[i];
                 if (expolygons_contain(this->_anchor_regions, line.a) && expolygons_contain(this->_anchor_regions, line.b)) {
@@ -129,8 +130,12 @@ bool BridgeDetector::detect_angle(double bridge_direction_override)
                     double len = line.length();
                     total_length += len;
                     max_length = std::max(max_length, len);
+                    archored_line_num++;
                 }
-            }        
+            }
+            if (clipped_lines.size() > 0 && archored_line_num > 0) {
+                candidates[i_angle].archored_percent = (double)archored_line_num / (double)clipped_lines.size();
+            }
         }
         if (total_length == 0.)
             continue;
@@ -155,7 +160,7 @@ bool BridgeDetector::detect_angle(double bridge_direction_override)
     // if any other direction is within extrusion width of coverage, prefer it if shorter
     // TODO: There are two options here - within width of the angle with most coverage, or within width of the currently perferred?
     size_t i_best = 0;
-    for (size_t i = 1; i < candidates.size() && candidates[i_best].coverage - candidates[i].coverage < this->spacing; ++ i)
+    for (size_t i = 1; i < candidates.size() && abs(candidates[i_best].archored_percent - candidates[i].archored_percent) < EPSILON; ++ i)
         if (candidates[i].max_length < candidates[i_best].max_length)
             i_best = i;
 
diff --git a/src/libslic3r/BridgeDetector.hpp b/src/libslic3r/BridgeDetector.hpp
index e97dd45c4..d422949cd 100644
--- a/src/libslic3r/BridgeDetector.hpp
+++ b/src/libslic3r/BridgeDetector.hpp
@@ -44,15 +44,16 @@ private:
     void initialize();
 
     struct BridgeDirection {
-        BridgeDirection(double a = -1.) : angle(a), coverage(0.), max_length(0.) {}
+        BridgeDirection(double a = -1.) : angle(a), coverage(0.), max_length(0.), archored_percent(0.){}
         // the best direction is the one causing most lines to be bridged (thus most coverage)
         bool operator<(const BridgeDirection &other) const {
             // Initial sort by coverage only - comparator must obey strict weak ordering
-            return this->coverage > other.coverage;
+            return this->archored_percent > other.archored_percent;
         };
         double angle;
         double coverage;
         double max_length;
+        double archored_percent;
     };
 
     // Get possible briging direction candidates.