Merge pull request #1167 from Geode-solutions/fix-repair-polygon-orientations

fix(RepairPolygonsOrientation): detect cases not orientable

Author: MelchiorSchuh

src/geode/mesh/helpers/repair_polygon_orientations.cpp

@@ -79,7 +79,7 @@ namespace
                 {
                     const auto adj =
                         mesh_.polygon_adjacent_edge( { cur_polygon, e } );
-                    if( !adj || visited[adj->polygon_id] )
+                    if( !adj )
                     {
                         continue;
                     }
@@ -89,6 +89,20 @@ namespace
                     const auto same_orientation =
                         ( vertices[e] == adj_vertices[1]
                             && vertices[e_next] == adj_vertices[0] );
+                    if( visited[adj->polygon_id] )
+                    {
+                        const auto is_valid =
+                            same_orientation
+                                ? cur_polygon_reorient
+                                      == reorient_polygon_[adj->polygon_id]
+                                : cur_polygon_reorient
+                                      != reorient_polygon_[adj->polygon_id];
+                        OPENGEODE_DATA_EXCEPTION( is_valid,
+                            "[RepairPolygonOrientations] Mobius "
+                            "strip detected, polygons orientations "
+                            "can not be repaired" );
+                        continue;
+                    }
                     const auto adj_polygon = adj->polygon_id;
                     visited[adj_polygon] = true;
                     reorient_polygon_[adj_polygon] =