From 77a2284f8a8a6c0542699d552ac970215c0577ba Mon Sep 17 00:00:00 2001
From: Thomas Krijnen <t.krijnen@gmail.com>
Date: Thu, 4 Jun 2026 21:37:41 +0200
Subject: [PATCH] Re-sew non-manifold operands; interior loop re-orientations
 affect edge identity #8140

---
 src/ifcgeom/kernels/opencascade/OpenCascadeKernel.cpp | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/src/ifcgeom/kernels/opencascade/OpenCascadeKernel.cpp b/src/ifcgeom/kernels/opencascade/OpenCascadeKernel.cpp
index e8b672906e..5284a26a5b 100644
--- a/src/ifcgeom/kernels/opencascade/OpenCascadeKernel.cpp
+++ b/src/ifcgeom/kernels/opencascade/OpenCascadeKernel.cpp
@@ -136,6 +136,17 @@ bool IfcGeom::OpenCascadeKernel::convert_openings(const IfcUtil::IfcBaseEntity*
 		for (auto entity_part : parts) {
 			bool is_manifold = util::is_manifold(entity_part);
 
+			if (!is_manifold) {
+				// force sewing, edge identity might have been mudied by FixAdvFace.FixOrientation.MSG5 to fix interior loop winding order
+                TopTools_ListOfShape list;
+                IfcGeom::util::shape_to_face_list(entity_part, list);
+                IfcGeom::util::create_solid_from_faces(list, entity_part, settings_.get<settings::Precision>().get(), true);
+                is_manifold = util::is_manifold(entity_part);
+                if (is_manifold) {
+					Logger::Warning("Successfully sewed non-manifold first operand");
+                }
+			}
+
 			if (!is_manifold) {
                 if (settings_.get<settings::MakeVolume>().get()) {
                     BOPAlgo_MakerVolume mv;