BUG: primitiveMesh: incorrect uncached edgeFaces. Fixes #2047.

It was only looking for faces that were used in both
endpoints but not actually checking whether they were indeed
an edge (== consecutive vertex) in all faces. So if one
face had an additional crossing edge and another didn't it
would find more edgeFaces than the proper
'primitiveMesh::edgeFaces()' routine.
This occasionally happened inside snappyHexMesh
(e.g. motorBike tutorial)

applications/utilities/mesh/advanced/modifyMesh/modifyMesh.C

@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
-    Copyright (C) 2016-2017 OpenCFD Ltd.
+    Copyright (C) 2016-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -365,12 +365,16 @@ int main(int argc, char *argv[])
     (
         dict.lookup("facesToTriangulate")
     );
+    // Optional
+    List<Pair<point>> facesToSplit;
+    dict.readIfPresent("facesToSplit", facesToSplit);
 
     bool cutBoundary =
     (
         pointsToMove.size()
      || edgesToSplit.size()
      || facesToTriangulate.size()
+     || facesToSplit.size()
     );
 
     List<Pair<point>> edgesToCollapse(dict.lookup("edgesToCollapse"));
@@ -388,6 +392,7 @@ int main(int argc, char *argv[])
         << "  Boundary cutting module:" << nl
         << "    points to move      :" << pointsToMove.size() << nl
         << "    edges to split      :" << edgesToSplit.size() << nl
+        << "    faces to split      :" << facesToSplit.size() << nl
         << "    faces to triangulate:" << facesToTriangulate.size() << nl
         << "  Cell splitting module:" << nl
         << "    cells to split      :" << cellsToPyramidise.size() << nl
@@ -481,6 +486,53 @@ int main(int argc, char *argv[])
     }
 
 
+    Info<< nl << "Looking up faces to split ..." << nl << endl;
+    Map<labelPair> faceToSplit(facesToSplit.size());
+    for (const Pair<point>& pts : facesToSplit)
+    {
+        label facei = findFace(mesh, allBoundary, pts.first());
+        if (facei == -1)
+        {
+            Info<< "Could not insert mesh face " << facei
+                << " for input point " << pts.first() << nl
+                << "Perhaps the face is already marked for splitting?" << endl;
+
+            validInputs = false;
+        }
+        else
+        {
+            // Find nearest points on face
+            const primitivePatch pp
+            (
+                SubList<face>(mesh.faces(), 1, facei),
+                mesh.points()
+            );
+
+            const label p0 = findPoint(pp, pts.first());
+            const label p1 = findPoint(pp, pts.second());
+
+            const face& f = mesh.faces()[facei];
+
+            if
+            (
+                p0 != -1
+             && p1 != -1
+             && faceToSplit.insert(facei, labelPair(f.find(p0), f.find(p1)))
+            )
+            {}
+            else
+            {
+                Info<< "Could not insert mesh face " << facei
+                    << " for input coordinates " << pts
+                    << " with vertices " << p0 << " and " << p1 << nl
+                    << "Perhaps the face is already marked for splitting?"
+                    << endl;
+
+            }
+        }
+    }
+DebugVar(faceToSplit);
+
 
     Info<< nl << "Looking up cells to convert to pyramids around"
         << " cell centre ..." << nl << endl;
@@ -652,7 +704,7 @@ int main(int argc, char *argv[])
         (
             pointToPos,
             edgeToCuts,
-            Map<labelPair>(0),  // Faces to split diagonally
+            faceToSplit,        // Faces to split diagonally
             faceToDecompose,    // Faces to triangulate
             meshMod
         );

etc/caseDicts/annotated/modifyMeshDict

@@ -30,6 +30,16 @@ edgesToSplit
     (( -0.17692 -0.45312 0.74516)( -0.18 -0.45 0.742))
 );
 
+// Split a boundary face:
+// The two coordinates indicate an edge on a face:
+//  - find the face where the first coordinate is on (so the point should be
+//    on the plane of the face
+//  - find nearest vertex on the face for both coordinates
+facesToSplit
+(
+    ((0.99 0 0.01)(0.99 0 0.99))    // edge (1 0 0)(1 0 1) on bottom face
+);
+
 // Triangulate a boundary face:
 // First coord is a point on the face to triangulate. It will introduce a
 // point on the face, triangulate and move the point to the second coordinate.

src/OpenFOAM/meshes/primitiveMesh/primitiveMeshEdgeFaces.C

@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2015 OpenFOAM Foundation
+    Copyright (C) 2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -68,7 +69,9 @@ const Foam::labelList& Foam::primitiveMesh::edgeFaces
     }
     else
     {
-        // Use the fact that pointEdges are sorted in incrementing edge order
+        // Use the fact that pointFaces are sorted in incrementing edge order
+        // (since they get constructed by inverting the faces which walks
+        //  in increasing face order)
         const edge& e = edges()[edgeI];
         const labelList& pFaces0 = pointFaces()[e[0]];
         const labelList& pFaces1 = pointFaces()[e[1]];
@@ -80,20 +83,38 @@ const Foam::labelList& Foam::primitiveMesh::edgeFaces
 
         while (i0 < pFaces0.size() && i1 < pFaces1.size())
         {
-            if (pFaces0[i0] < pFaces1[i1])
+            const label f0 = pFaces0[i0];
+            const label f1 = pFaces1[i1];
+
+            if (f0 < f1)
             {
                 ++i0;
             }
-            else if (pFaces0[i0] > pFaces1[i1])
+            else if (f0 > f1)
             {
                 ++i1;
             }
             else
             {
-                // Equal. Append.
+                // Equal face. Check if indeed on consecutive vertices on both
-                storage.append(pFaces0[i0]);
+                // faces since it could be that there is an 'ear' where one
-                ++i0;
+                // side is a triangle  and the other side is part of a bigger
-                ++i1;
+                // face (e.g. quad). Now all vertex-vertex pairs on the
+                // triangle are edges but there is no cross connection on the
+                // bigger face.
+                const face& f = faces()[f0];
+                const label fp0 = f.find(e[0]);
+
+                if (f[f.fcIndex(fp0)] == e[1] || f[f.rcIndex(fp0)] == e[1])
+                {
+                    storage.append(f0);
+                    ++i0;
+                    ++i1;
+                }
+                else
+                {
+                    ++i1;
+                }
             }
         }