From c3f352c0184678faa84623b51927516162290ee8 Mon Sep 17 00:00:00 2001
From: Thomas Krijnen <t.krijnen@gmail.com>
Date: Sun, 6 Aug 2023 14:27:31 +0800
Subject: [PATCH] #3546 Filter duplicate edge indices

---
 .../IfcGeomRepresentation.cpp                 | 30 +++++++++++--------
 .../IfcGeomRepresentation.h                   |  2 +-
 2 files changed, 19 insertions(+), 13 deletions(-)

diff --git a/src/ifcgeom_schema_agnostic/IfcGeomRepresentation.cpp b/src/ifcgeom_schema_agnostic/IfcGeomRepresentation.cpp
index 7b0bd95756..e606304b63 100644
--- a/src/ifcgeom_schema_agnostic/IfcGeomRepresentation.cpp
+++ b/src/ifcgeom_schema_agnostic/IfcGeomRepresentation.cpp
@@ -268,6 +268,10 @@ IfcGeom::Representation::Triangulation::Triangulation(const BRep& shape_model)
 		weld_offset_ += welds.size();
 		welds.clear();
 
+		// When welding vertices, vertex coords will be shared among faces so we need to per-shape set
+		// to keep track of which edges were already emitted.
+		std::set<std::pair<int, int>> emitted_edges;
+
 		int surface_style_id = -1;
 		if (iit->hasStyle()) {
 			Material adapter(iit->StylePtr());
@@ -319,7 +323,6 @@ IfcGeom::Representation::Triangulation::Triangulation(const BRep& shape_model)
 				// Keep track of the number of times an edge is used
 				// Manifold edges (i.e. edges used twice) are deemed invisible
 				std::map<std::pair<int, int>, int> edgecount;
-				std::vector<std::pair<int, int> > edges_temp;
 
 				std::vector<gp_XYZ> coords;
 				BRepGProp_Face prop(face);
@@ -389,15 +392,20 @@ IfcGeom::Representation::Triangulation::Triangulation(const BRep& shape_model)
 					_material_ids.push_back(surface_style_id);
 					_item_ids.push_back(iit->ItemId());
 
-					addEdge(dict[n1], dict[n2], edgecount, edges_temp);
-					addEdge(dict[n2], dict[n3], edgecount, edges_temp);
-					addEdge(dict[n3], dict[n1], edgecount, edges_temp);
+					addEdge(dict[n1], dict[n2], edgecount);
+					addEdge(dict[n2], dict[n3], edgecount);
+					addEdge(dict[n3], dict[n1], edgecount);
 				}
-				for (std::vector<std::pair<int, int> >::const_iterator jt = edges_temp.begin(); jt != edges_temp.end(); ++jt) {
-					if (edgecount[*jt] == 1) {
+				for (auto& p : edgecount) {
+					// @todo should be != 2?
+					if (p.second == 1 && emitted_edges.find(p.first) == emitted_edges.end()) {
 						// non manifold edge, face boundary
-						_edges.push_back(jt->first);
-						_edges.push_back(jt->second);
+						_edges.push_back(p.first.first);
+						_edges.push_back(p.first.second);
+						if (settings().get(IteratorSettings::WELD_VERTICES)) {
+							// only relevant while welding, because otherwise vertices are not shared among distinct faces
+							emitted_edges.insert(p.first);
+						}
 					}
 				}
 			}
@@ -526,9 +534,7 @@ int IfcGeom::Representation::Triangulation::addVertex(int item_index, int materi
 	return i;
 }
 
-void IfcGeom::Representation::Triangulation::addEdge(int n1, int n2, std::map<std::pair<int, int>, int>& edgecount, std::vector<std::pair<int, int>>& edges_temp) {
+void IfcGeom::Representation::Triangulation::addEdge(int n1, int n2, std::map<std::pair<int, int>, int>& edgecount) {
 	const Edge e = Edge((std::min)(n1, n2), (std::max)(n1, n2));
-	if (edgecount.find(e) == edgecount.end()) edgecount[e] = 1;
-	else edgecount[e] ++;
-	edges_temp.push_back(e);
+	edgecount[e] ++;
 }
diff --git a/src/ifcgeom_schema_agnostic/IfcGeomRepresentation.h b/src/ifcgeom_schema_agnostic/IfcGeomRepresentation.h
index 2762e40321..0d7df7d7d1 100644
--- a/src/ifcgeom_schema_agnostic/IfcGeomRepresentation.h
+++ b/src/ifcgeom_schema_agnostic/IfcGeomRepresentation.h
@@ -176,7 +176,7 @@ namespace IfcGeom {
 		private:
 			/// Welds vertices that belong to different faces
 			int addVertex(int item_index, int material_index, const gp_XYZ& p);
-			void addEdge(int n1, int n2, std::map<std::pair<int, int>, int>& edgecount, std::vector<std::pair<int, int> >& edges_temp);
+			void addEdge(int n1, int n2, std::map<std::pair<int, int>, int>& edgecount);
 
 			Triangulation();
 			Triangulation(const Triangulation&);