ENH: add ensight writeBox method (eg, for simple 'placeholder' geometry)

- related to issue #3095. Some type of geometry is required when
  loading "measured" ensight data.

ENH: emit a fallback geometry-box for foamToEnsight

- eg, with "foamToEnsight -no-internal -no-boundary" and lagrangian

src/fileFormats/ensight/mesh/ensightMesh.C

@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2016-2022 OpenCFD Ltd.
+    Copyright (C) 2016-2024 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -449,6 +449,19 @@ void Foam::ensightMesh::write
     {
         faceZoneParts_[id].write(os, mesh_, parallel);
     }
+
+    // No geometry parts written?
+    // - with lagrangian-only output the VTK EnsightReader still
+    //   needs a volume geometry, and ensight usually does too
+    if
+    (
+        cellZoneParts_.empty()
+     && boundaryParts_.empty()
+     && faceZoneParts_.empty()
+    )
+    {
+        ensightCells::writeBox(os, mesh_.bounds());
+    }
 }
 
 

src/fileFormats/ensight/mesh/ensightMesh.H

@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2016-2022 OpenCFD Ltd.
+    Copyright (C) 2016-2024 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -216,18 +216,22 @@ public:
 
     // Output
 
-        //- Write geometry to file. Normally in parallel
+        //- Write geometry to file (normally in parallel).
+        //  If all geometry is disabled, it will simply writes the mesh
+        //  bounding box (to ensure that the geometry file is non-empty)
         void write
         (
             ensightGeoFile& os,
-            bool parallel = Pstream::parRun()
+            bool parallel = UPstream::parRun()
         ) const;
 
-        //- Write geometry to file. Normally in parallel
+        //- Write geometry to file (normally in parallel).
+        //  If all geometry is disabled, it will simply writes the mesh
+        //  bounding box (to ensure that the geometry file is non-empty)
         inline void write
         (
             autoPtr<ensightGeoFile>& os,
-            bool parallel = Pstream::parRun()
+            bool parallel = UPstream::parRun()
         ) const;
 };
 

src/fileFormats/ensight/part/cells/ensightCells.H

@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2016-2022 OpenCFD Ltd.
+    Copyright (C) 2016-2024 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -46,6 +46,7 @@ namespace Foam
 
 // Forward Declarations
 class bitSet;
+class boundBox;
 class polyMesh;
 template<class T> class InfoProxy;
 
@@ -279,6 +280,16 @@ public:
             const polyMesh& mesh,
             bool parallel
         ) const;
+
+        //- Write bounding box geometry.
+        //- All parameters are only relevant on master
+        static void writeBox
+        (
+            ensightGeoFile& os,
+            const boundBox& bb,
+            const label partIndex = 0,
+            const word& partName = "geometry-box"
+        );
 };
 
 

src/fileFormats/ensight/part/cells/ensightCellsIO.C

@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2020 OpenCFD Ltd.
+    Copyright (C) 2020-2024 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -28,7 +28,9 @@ License
 #include "ensightCells.H"
 #include "ensightOutput.H"
 #include "InfoProxy.H"
+#include "boundBox.H"
 #include "polyMesh.H"
+#include "cellModel.H"
 #include "globalIndex.H"
 #include "globalMeshData.H"
 #include "manifoldCellsMeshObject.H"
@@ -330,6 +332,44 @@ void Foam::ensightCells::write
 }
 
 
+void Foam::ensightCells::writeBox
+(
+    ensightGeoFile& os,
+    const boundBox& bb,
+    const label partIndex,
+    const word& partName
+)
+{
+    pointField points;
+    cellShapeList shapes;
+
+    if (UPstream::master())
+    {
+        points = bb.hexCorners();
+        shapes.emplace_back(cellModel::HEX, identity(8));
+    }
+
+    ensightOutput::Detail::writeCoordinates
+    (
+        os,
+        partIndex,
+        partName,
+        8,          // nPoints (global)
+        points,
+        false       // serial only! (parallel=false)
+    );
+
+    if (UPstream::master())
+    {
+        os.writeKeyword(ensightCells::key(ensightCells::elemType::HEXA8));
+        os.write(shapes.size());  // one cell (global)
+        os.newline();
+
+        ensightOutput::writeCellShapes(os, shapes);
+    }
+}
+
+
 // * * * * * * * * * * * * * * * Ostream Operator  * * * * * * * * * * * * * //
 
 template<>

src/finiteArea/output/ensight/ensightFaMesh.H

@@ -148,14 +148,14 @@ public:
         void write
         (
             ensightGeoFile& os,
-            bool parallel = Pstream::parRun()
+            bool parallel = UPstream::parRun()
         ) const;
 
         //- Write geometry to file. Normally in parallel
         inline void write
         (
             autoPtr<ensightGeoFile>& os,
-            bool parallel = Pstream::parRun()
+            bool parallel = UPstream::parRun()
         ) const;
 };