From 2f146f727b1cd52a59e63ddf546815747fcb4229 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The projection algorithm was originally made for custom supports, so vertical triangles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 9738a001614..44b1fcff1e4 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 5de612d32c4..46873ff06c2 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) {