From 1904b7b904597d9e9a8a77deeb1a9d9cab604b03 Mon Sep 17 00:00:00 2001
From: Lukas Matena <lukasmatena@seznam.cz>
Date: Fri, 19 Feb 2021 10:57:18 +0100
Subject: [PATCH] Bugfix: custom seam did not work for triangles that were
 exactly vertical

The projection algorithm was originally made for custom supports, so vertical triangles
were not interesting. They are for seam. Instead of rewriting the algorithm and risking
more bugs, the edge case is detected and the triangle is tilted slightly.
---
 src/libslic3r/GCode/SeamPlacer.cpp | 53 +++++++++++++++---------------
 src/libslic3r/PrintObject.cpp      |  5 +++
 2 files changed, 32 insertions(+), 26 deletions(-)

diff --git a/src/libslic3r/GCode/SeamPlacer.cpp b/src/libslic3r/GCode/SeamPlacer.cpp
index 9738a0016..44b1fcff1 100644
--- a/src/libslic3r/GCode/SeamPlacer.cpp
+++ b/src/libslic3r/GCode/SeamPlacer.cpp
@@ -750,35 +750,36 @@ void SeamPlacer::apply_custom_seam(const Polygon& polygon, size_t po_idx,
         }
     }
 
-////////////////////////
-//    std::ostringstream os;
-//    os << std::setw(3) << std::setfill('0') << layer_id;
-//    int a = scale_(30.);
-//    SVG svg("custom_seam" + os.str() + ".svg", BoundingBox(Point(-a, -a), Point(a, a)));
-//    //if (! m_enforcers[po_idx].empty())
-//    //    svg.draw(m_enforcers[po_idx][layer_id].polys, "blue");
-//    //if (! m_blockers[po_idx].empty())
-//    //    svg.draw(m_blockers[po_idx][layer_id].polys, "red");
+#if 0
+    std::ostringstream os;
+    os << std::setw(3) << std::setfill('0') << layer_id;
+    int a = scale_(30.);
+    SVG svg("custom_seam" + os.str() + ".svg", BoundingBox(Point(-a, -a), Point(a, a)));
+    if (! m_enforcers[po_idx].empty())
+        svg.draw(m_enforcers[po_idx][layer_id].polys, "blue");
+    if (! m_blockers[po_idx].empty())
+        svg.draw(m_blockers[po_idx][layer_id].polys, "red");
+
+    if (! blockers_idxs.empty()) {
+        ;
+    }
 
 
+    size_t min_idx = std::min_element(penalties.begin(), penalties.end()) - penalties.begin();
 
-//    size_t min_idx = std::min_element(penalties.begin(), penalties.end()) - penalties.begin();
-
-//    //svg.draw(polygon.points[idx_min], "red", 6e5);
-//    for (size_t i=0; i<polygon.points.size(); ++i) {
-//        std::string fill;
-//        coord_t size = 0;
-//        if (min_idx == i) {
-//            fill = "yellow";
-//            size = 5e5;
-//        } else
-//            fill = (std::find(enforcers_idxs.begin(), enforcers_idxs.end(), i) != enforcers_idxs.end() ? "green" : "black");
-//        if (i != 0)
-//            svg.draw(polygon.points[i], fill, size);
-//        else
-//            svg.draw(polygon.points[i], "red", 5e5);
-//    }
-//////////////////////
+    for (size_t i=0; i<polygon.points.size(); ++i) {
+        std::string fill;
+        coord_t size = 5e5;
+        if (min_idx == i)
+            fill = "yellow";
+        else
+            fill = (std::find(blockers_idxs.begin(), blockers_idxs.end(), i) != blockers_idxs.end() ? "green" : "black");
+        if (i != 0)
+            svg.draw(polygon.points[i], fill, size);
+        else
+            svg.draw(polygon.points[i], "red", 5e5);
+    }
+#endif
 
 }
 
diff --git a/src/libslic3r/PrintObject.cpp b/src/libslic3r/PrintObject.cpp
index 5de612d32..46873ff06 100644
--- a/src/libslic3r/PrintObject.cpp
+++ b/src/libslic3r/PrintObject.cpp
@@ -2845,6 +2845,11 @@ void PrintObject::project_and_append_custom_facets(
             if (! seam && tr_det_sign * z_comp > 0.)
                 continue;
 
+            // The algorithm does not process vertical triangles, but it should for seam.
+            // In that case, tilt the triangle a bit so the projection does not degenerate.
+            if (seam && z_comp == 0.f)
+                facet[0].x() += float(EPSILON);
+
             // Sort the three vertices according to z-coordinate.
             std::sort(facet.begin(), facet.end(),
                       [](const Vec3f& pt1, const Vec3f&pt2) {