ENH: general boundBox/treeBoundBox improvements

- null() static method
  * as const reference to the invertedBox with the appropriate casting.

- boundBox inflate(random)
  * refactored from treeBoundBox::extend, but allows in-place modification

- boundBox::hexFaces() instead of boundBox::faces
  * rarely used, but avoids confusion with treeBoundBox::faces
    and reuses hexCell face definitions without code duplication

- boundBox::hexCorners() for corner points corresponding to a hexCell.
  Can also be accessed from a treeBoundBox without ambiguity with
  points(), which could be hex corners (boundBox) or octant corners
  (treeBoundBox)

- boundBox::add with pairs of points
  * convenient (for example) when adding edges or a 'box' that has
    been extracted from a primitive mesh shape.

- declare boundBox nPoints(), nFaces(), nEdges() as per hexCell

ENH: return invertedBox instead of FatalError for empty trees

- similar to #2612

ENH: cellShape(HEX, ...) + boundBox hexCorners for block meshes

STYLE: cellModel::ref(...) instead of de-reference cellModel::ptr(...)

applications/test/boundBox/Test-boundBox.C

@@ -34,7 +34,6 @@ Description
 #include "line.H"
 #include "Random.H"
 #include "treeBoundBox.H"
-#include "cellModel.H"
 #include "bitSet.H"
 #include "HashSet.H"
 #include "ListOps.H"
@@ -59,8 +58,7 @@ int main(int argc, char *argv[])
 {
     #include "setRootCase.H"
 
-    Info<<"boundBox faces: " << boundBox::faces << nl
-        <<"hex faces: " << cellModel::ref(cellModel::HEX).modelFaces() << nl
+    Info<<"boundBox faces: " << boundBox::hexFaces() << nl
         <<"tree-bb faces: " << treeBoundBox::faces << nl
         <<"tree-bb edges: " << treeBoundBox::edges << endl;
 
@@ -113,10 +111,8 @@ int main(int argc, char *argv[])
         Info<<"enclose point " << pt << " -> " << bb << endl;
 
         // restart with same points
-        bb = boundBox::invertedBox;
-        bb.add(point(1,1,1));
-        bb.add(point::zero);
-        bb.add(point(0,1.5,0.5));
+        bb.reset(point::zero);
+        bb.add(point(1,1,1), point(0,1.5,0.5));
         bb.add(point(5,2,-2));
 
         Info<<"repeated " << bb << endl;

applications/utilities/mesh/conversion/ensightToFoam/ensightMeshReader.C

@@ -293,7 +293,7 @@ bool Foam::fileFormats::ensightMeshReader::readGoldPart
                 elemIdToCells
             );
 
-            const auto& model = *cellModel::ptr(cellModel::TET);
+            const auto& model = cellModel::ref(cellModel::TET);
             for (label shapei = 0; shapei < nShapes; shapei++)
             {
                 readVerts(is, 4, nodeIdToPoints, verts);
@@ -326,7 +326,7 @@ bool Foam::fileFormats::ensightMeshReader::readGoldPart
                 elemIdToCells
             );
 
-            const auto& model = *cellModel::ptr(cellModel::PYR);
+            const auto& model = cellModel::ref(cellModel::PYR);
             for (label shapei = 0; shapei < nShapes; shapei++)
             {
                 readVerts(is, 5, nodeIdToPoints, verts);
@@ -359,7 +359,7 @@ bool Foam::fileFormats::ensightMeshReader::readGoldPart
                 elemIdToCells
             );
 
-            const auto& model = *cellModel::ptr(cellModel::PRISM);
+            const auto& model = cellModel::ref(cellModel::PRISM);
             for (label shapei = 0; shapei < nShapes; shapei++)
             {
                 readVerts(is, 6, nodeIdToPoints, verts);
@@ -392,7 +392,7 @@ bool Foam::fileFormats::ensightMeshReader::readGoldPart
                 elemIdToCells
             );
 
-            const auto& model = *cellModel::ptr(cellModel::HEX);
+            const auto& model = cellModel::ref(cellModel::HEX);
             for (label shapei = 0; shapei < nShapes; shapei++)
             {
                 readVerts(is, 8, nodeIdToPoints, verts);

applications/utilities/preProcessing/PDR/pdrFields/obstacles/PDRobstacle.C

@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2019-2021 OpenCFD Ltd.
+    Copyright (C) 2019-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -389,7 +389,7 @@ Foam::meshedSurface Foam::PDRobstacle::surface() const
             boundBox box(obs.pt, obs.pt + obs.span);
 
             pointField pts(box.points());
-            faceList fcs(boundBox::faces);
+            faceList fcs(boundBox::hexFaces());
 
             surf.transfer(pts, fcs);
 
@@ -436,7 +436,7 @@ Foam::meshedSurface Foam::PDRobstacle::surface() const
             );
 
             pointField pts0(box.points());
-            faceList fcs(boundBox::faces);
+            faceList fcs(boundBox::hexFaces());
 
             pointField pts(cs.globalPosition(pts0));
 

applications/utilities/preProcessing/createBoxTurb/createBlockMesh.H

@@ -1,5 +1,3 @@
-const cellModel& hex = cellModel::ref(cellModel::HEX);
-
 cellShapeList cellShapes;
 faceListList boundary;
 pointField points;
@@ -8,20 +6,8 @@ pointField points;
 
     block b
     (
-        cellShape(hex, identity(8)),
-        pointField
-        (
-            {
-                point(0, 0, 0),
-                point(L.x(), 0, 0),
-                point(L.x(), L.y(), 0),
-                point(0, L.y(), 0),
-                point(0, 0, L.z()),
-                point(L.x(), 0, L.z()),
-                point(L.x(), L.y(), L.z()),
-                point(0, L.y(), L.z())
-            }
-        ),
+        cellShape(cellModel::HEX, identity(8)),
+        pointField(boundBox(point::zero, L).hexCorners()),
         blockEdgeList(),
         blockFaceList(),
         N