ENH: bounding box clipping for ensightWrite function object (issue #973)

- for larger problems with a smaller region of interest, can apply a
  bounding to limit the size of the ensight geometry and fields created.

  Since the implementation uses a fvMeshSubset, there is an additional
  per-process memory overhead.

  A high output frequency should be avoided with moving meshes, since
  this indirectly forces a frequent update of the submesh.

src/functionObjects/utilities/Make/options

@@ -4,6 +4,7 @@ EXE_INC = \
     -I$(LIB_SRC)/fileFormats/lnInclude \
     -I$(LIB_SRC)/conversion/lnInclude \
     -I$(LIB_SRC)/sampling/lnInclude \
+    -I$(LIB_SRC)/dynamicMesh/lnInclude \
     -I$(LIB_SRC)/ODE/lnInclude \
     -I$(LIB_SRC)/thermophysicalModels/basic/lnInclude \
     -I$(LIB_SRC)/transportModels/compressible/lnInclude
@@ -13,6 +14,7 @@ LIB_LIBS = \
     -lfiniteArea \
     -lconversion \
     -lsampling \
+    -ldynamicMesh \
     -lfluidThermophysicalModels \
     -lcompressibleTransportModels \
     -lODE

src/functionObjects/utilities/ensightWrite/ensightWrite.C

@@ -47,6 +47,39 @@ namespace functionObjects
 
 // * * * * * * * * * * * * * Private Member Functions  * * * * * * * * * * * //
 
+Foam::bitSet Foam::functionObjects::ensightWrite::cellSelection() const
+{
+    bitSet cellsToSelect;
+
+    // Could also deal with cellZones here, as required
+
+    if (bounds_.empty())
+    {
+        return cellsToSelect;
+    }
+
+
+    const auto& cellCentres = static_cast<const fvMesh&>(mesh_).C();
+
+    const label len = mesh_.nCells();
+
+    cellsToSelect.resize(len);
+
+    for (label celli=0; celli < len; ++celli)
+    {
+        const point& cc = cellCentres[celli];
+
+        if (bounds_.contains(cc))
+        {
+            cellsToSelect.set(celli);
+        }
+    }
+
+    return cellsToSelect;
+}
+
+
+
 int Foam::functionObjects::ensightWrite::process(const word& fieldName)
 {
     int state = 0;
@@ -83,7 +116,8 @@ Foam::functionObjects::ensightWrite::ensightWrite
     caseOpts_(writeOpts_.format()),
     selectFields_(),
     dirName_("ensightWrite"),
-    consecutive_(false)
+    consecutive_(false),
+    bounds_()
 {
     if (postProcess)
     {
@@ -104,6 +138,12 @@ bool Foam::functionObjects::ensightWrite::read(const dictionary& dict)
 {
     fvMeshFunctionObject::read(dict);
 
+    // Ensure consistency
+
+    meshSubset_.clear();
+    ensMesh_.clear();
+
+
     //
     // writer options
     //
@@ -123,6 +163,10 @@ bool Foam::functionObjects::ensightWrite::read(const dictionary& dict)
     }
 
 
+    bounds_.clear();
+    dict.readIfPresent("bounds", bounds_);
+
+
     //
     // case options
     //
@@ -197,7 +241,25 @@ bool Foam::functionObjects::ensightWrite::write()
     if (!ensMesh_.valid())
     {
         writeGeom = true;
-        ensMesh_.reset(new ensightMesh(mesh_, writeOpts_));
+
+        bitSet selection = this->cellSelection();
+
+        if (returnReduce(!selection.empty(), orOp<bool>()))
+        {
+            meshSubset_.clear();
+            meshSubset_.reset(new fvMeshSubset(mesh_, selection));
+            ensMesh_.reset
+            (
+                new ensightMesh(meshSubset_->subMesh(), writeOpts_)
+            );
+        }
+        else
+        {
+            ensMesh_.reset
+            (
+                new ensightMesh(mesh_, writeOpts_)
+            );
+        }
     }
     if (ensMesh_().needsUpdate())
     {
@@ -219,12 +281,12 @@ bool Foam::functionObjects::ensightWrite::write()
     DynamicList<word> missing(selectFields_.size());
     DynamicList<word> ignored(selectFields_.size());
 
-    // check exact matches first
+    // Check exact matches first
     for (const wordRe& select : selectFields_)
     {
         if (!select.isPattern())
         {
-            const word& fieldName = static_cast<const word&>(select);
+            const word& fieldName = select;
 
             if (!candidates.erase(fieldName))
             {
@@ -271,7 +333,14 @@ void Foam::functionObjects::ensightWrite::updateMesh(const mapPolyMesh& mpm)
 {
     // fvMeshFunctionObject::updateMesh(mpm);
 
-    if (ensMesh_.valid())
+    // This is heavy-handed, but with a bounding-box limited sub-mesh,
+    // we don't readily know if the updates affect the subsetted mesh.
+    if (!bounds_.empty())
+    {
+        ensMesh_.clear();
+        meshSubset_.clear();
+    }
+    else if (ensMesh_.valid())
     {
         ensMesh_->expire();
     }
@@ -282,7 +351,14 @@ void Foam::functionObjects::ensightWrite::movePoints(const polyMesh& mpm)
 {
     // fvMeshFunctionObject::updateMesh(mpm);
 
-    if (ensMesh_.valid())
+    // This is heavy-handed, but with a bounding-box limited sub-mesh,
+    // we don't readily know if the updates affect the subsetted mesh.
+    if (!bounds_.empty())
+    {
+        ensMesh_.clear();
+        meshSubset_.clear();
+    }
+    else if (ensMesh_.valid())
     {
         ensMesh_->expire();
     }

src/functionObjects/utilities/ensightWrite/ensightWrite.H

@@ -67,6 +67,7 @@ Description
         faceZones    | Select faceZones to write    | no        |
         consecutive  | Consecutive output numbering | no        | false
         nodeValues   | Write values at nodes        | no        | false
+        bounds       | Limit with a bounding box    | no        |
     \endtable
 
     Note that if the \c patches entry is an empty list, this will select all
@@ -93,6 +94,7 @@ SourceFiles
 
 #include "interpolation.H"
 #include "volFields.H"
+#include "fvMeshSubset.H"
 #include "surfaceFields.H"
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
@@ -129,6 +131,12 @@ class ensightWrite
         //- Consecutive output numbering
         bool consecutive_;
 
+        //- Restrict to bounding box
+        boundBox bounds_;
+
+        //- Mesh subset handler
+        autoPtr<fvMeshSubset> meshSubset_;
+
         //- Ensight case handler
         autoPtr<ensightCase> ensCase_;
 
@@ -150,6 +158,9 @@ class ensightWrite
             return *ensMesh_;
         }
 
+        //- Define cell selection from bounding box.
+        //  An empty set if no bounding box is specified.
+        bitSet cellSelection() const;
 
         //- Apply for the volume field type
         template<class Type>

src/functionObjects/utilities/ensightWrite/ensightWriteTemplates.C

@@ -38,20 +38,39 @@ int Foam::functionObjects::ensightWrite::writeVolField
     // State: return 0 (not-processed), -1 (skip), +1 ok
     typedef GeometricField<Type, fvPatchField, volMesh> VolFieldType;
 
+    const VolFieldType* fldPtr;
+
     // Already done, or not available
-    if (state || !foundObject<VolFieldType>(inputName))
+    if (state || !(fldPtr = lookupObjectPtr<VolFieldType>(inputName)))
     {
         return state;
     }
 
     autoPtr<ensightFile> os = ensCase().newData<Type>(inputName);
-    ensightOutput::writeField<Type>
-    (
-        lookupObject<VolFieldType>(inputName),
-        ensMesh(),
-        os,
-        caseOpts_.nodeValues()
-    );
+
+
+    if (meshSubset_.valid())
+    {
+        tmp<VolFieldType> tfield = meshSubset_->interpolate(*fldPtr);
+
+        ensightOutput::writeField<Type>
+        (
+            tfield(),
+            ensMesh(),
+            os,
+            caseOpts_.nodeValues()
+        );
+    }
+    else
+    {
+        ensightOutput::writeField<Type>
+        (
+            *fldPtr,
+            ensMesh(),
+            os,
+            caseOpts_.nodeValues()
+        );
+    }
 
     Log << " " << inputName;
 

tutorials/incompressible/simpleFoam/windAroundBuildings/Allrun-parallel

@@ -0,0 +1,16 @@
+#!/bin/sh
+cd ${0%/*} || exit 1                        # Run from this directory
+. $WM_PROJECT_DIR/bin/tools/RunFunctions    # Tutorial run functions
+
+runApplication surfaceFeatureExtract
+
+runApplication blockMesh
+runApplication snappyHexMesh -overwrite
+
+runApplication decomposePar
+
+runParallel $(getApplication)
+
+runApplication reconstructPar
+
+#------------------------------------------------------------------------------

tutorials/incompressible/simpleFoam/windAroundBuildings/system/decomposeParDict

@@ -0,0 +1,23 @@
+/*--------------------------------*- C++ -*----------------------------------*\
+| =========                 |                                                 |
+| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
+|  \\    /   O peration     | Version:  v1806                                 |
+|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |
+|    \\/     M anipulation  |                                                 |
+\*---------------------------------------------------------------------------*/
+FoamFile
+{
+    version     2.0;
+    format      ascii;
+    class       dictionary;
+    object      decomposeParDict;
+}
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+numberOfSubdomains 6;
+
+// method          kahip;
+method          scotch;
+
+
+// ************************************************************************* //

tutorials/incompressible/simpleFoam/windAroundBuildings/system/ensightWrite

@@ -12,6 +12,9 @@ ensightWrite
     // Fields to output (words or regex)
     fields  (U p "(k|epsilon|omega)");
 
+    // Limit output region
+    bounds  (0 0 0) (245 180 80);
+
     //- Write more frequent than fields
     writeControl    timeStep;
     writeInterval   5;