From 8df74588841e63e4cae63ff8f844779013aabcbd Mon Sep 17 00:00:00 2001
From: Filip Sykala <filip.sykala@prusa3d.cz>
Date: Thu, 18 Mar 2021 12:10:09 +0100
Subject: [PATCH] use geometry orientation

---
 .../SLA/SupportIslands/PointUtils.cpp         |  9 --------
 .../SLA/SupportIslands/PointUtils.hpp         |  3 ---
 .../SLA/SupportIslands/VoronoiGraphUtils.cpp  | 22 ++++++++++++-------
 src/libslic3r/SLA/SupportPointGenerator.cpp   |  2 ++
 4 files changed, 16 insertions(+), 20 deletions(-)

diff --git a/src/libslic3r/SLA/SupportIslands/PointUtils.cpp b/src/libslic3r/SLA/SupportIslands/PointUtils.cpp
index 3876b1d063..e15524384d 100644
--- a/src/libslic3r/SLA/SupportIslands/PointUtils.cpp
+++ b/src/libslic3r/SLA/SupportIslands/PointUtils.cpp
@@ -2,12 +2,3 @@
 
 using namespace Slic3r::sla;
 
-bool PointUtils::is_ccw(const Point &p1, const Point &p2, const Point &center)
-{
-    Slic3r::Point v1 = p1 - center;
-    Slic3r::Point v2 = p2 - center;
-
-    double cross_product = v1.x() * (double) v2.y() -
-                           v2.x() * (double) v1.y();
-    return cross_product > 0;
-}
diff --git a/src/libslic3r/SLA/SupportIslands/PointUtils.hpp b/src/libslic3r/SLA/SupportIslands/PointUtils.hpp
index 5e7099cfed..21861f3034 100644
--- a/src/libslic3r/SLA/SupportIslands/PointUtils.hpp
+++ b/src/libslic3r/SLA/SupportIslands/PointUtils.hpp
@@ -14,9 +14,6 @@ class PointUtils
 {
 public:
     PointUtils() = delete;
-
-    // is point p1 to p2 in counter clock wise order against center?
-    static bool is_ccw(const Point &p1, const Point &p2, const Point &center);
 };
 
 } // namespace Slic3r::sla
diff --git a/src/libslic3r/SLA/SupportIslands/VoronoiGraphUtils.cpp b/src/libslic3r/SLA/SupportIslands/VoronoiGraphUtils.cpp
index d29040593f..56aa476d06 100644
--- a/src/libslic3r/SLA/SupportIslands/VoronoiGraphUtils.cpp
+++ b/src/libslic3r/SLA/SupportIslands/VoronoiGraphUtils.cpp
@@ -214,20 +214,26 @@ Slic3r::Polygon VoronoiGraphUtils::to_polygon(const VD::cell_type & cell,
                                               const Slic3r::Points &points,
                                               double maximal_distance)
 {
-    const VD::edge_type *edge = cell.incident_edge();
     Lines lines;
     Point center = points[cell.source_index()];
     // Convenient way to iterate edges around Voronoi cell.
+    const VD::edge_type *edge = cell.incident_edge();
     do {
         assert(edge->is_linear());
-        if (edge->is_primary()) {
-            std::optional<Line> line = to_line(*edge, points, maximal_distance);
-            if (line.has_value()) {
-                if (!PointUtils::is_ccw(line->a, line->b, center))
-                    std::swap(line->a, line->b);
-                lines.push_back(line.value());
-            }
+        if (!edge->is_primary()) {
+            edge = edge->next();
+            continue;
         }
+        std::optional<Line> line = to_line(*edge, points, maximal_distance);
+        if (!line.has_value()) {
+            edge = edge->next();
+            continue;            
+        }
+        Geometry::Orientation o = Geometry::orient(center, line->a, line->b);
+        assert(o != Geometry::Orientation::ORIENTATION_COLINEAR);
+        if (o == Geometry::Orientation::ORIENTATION_CW)
+            std::swap(line->a, line->b);
+        lines.push_back(line.value());
         edge = edge->next();
     } while (edge != cell.incident_edge());
     LineUtils::sort_CCW(lines, center);
diff --git a/src/libslic3r/SLA/SupportPointGenerator.cpp b/src/libslic3r/SLA/SupportPointGenerator.cpp
index e315c9b4e6..389f032e3b 100644
--- a/src/libslic3r/SLA/SupportPointGenerator.cpp
+++ b/src/libslic3r/SLA/SupportPointGenerator.cpp
@@ -355,6 +355,8 @@ SupportIslandPoints SupportPointGenerator::uniform_cover_island(
     SupportIslandPoints  samples = SampleIslandUtils::sample_voronoi_graph(
             skeleton, config, longest_path);
 
+    SampleIslandUtils::align_samples(samples, island, config);
+
 #ifdef SLA_SUPPORTPOINTGEN_DEBUG
     const char* support_point_color = "lightgreen";
     coord_t     support_point_radius = config.head_radius;