diff --git a/src/OpenFOAM/Make/files b/src/OpenFOAM/Make/files
index c63626f245..d0e703cfd1 100644
--- a/src/OpenFOAM/Make/files
+++ b/src/OpenFOAM/Make/files
@@ -820,12 +820,14 @@ $(interpolationWeights)/linearInterpolationWeights/linearInterpolationWeights.C
 $(interpolationWeights)/splineInterpolationWeights/splineInterpolationWeights.C
 
 
-algorithms/indexedOctree/indexedOctreeName.C
+algorithms/AABBTree/AABBTreeBase.C
+
+algorithms/indexedOctree/indexedOctreeBase.C
 algorithms/indexedOctree/treeDataCell.C
 algorithms/indexedOctree/treeDataEdge.C
 algorithms/indexedOctree/treeDataPoint.C
 
-algorithms/dynamicIndexedOctree/dynamicIndexedOctreeName.C
+algorithms/dynamicIndexedOctree/dynamicIndexedOctreeBase.C
 algorithms/dynamicIndexedOctree/dynamicTreeDataPoint.C
 
 parallel/commSchedule/commSchedule.C
diff --git a/src/OpenFOAM/algorithms/AABBTree/AABBTree.C b/src/OpenFOAM/algorithms/AABBTree/AABBTree.C
index df4a4c48e4..3ba025cab5 100644
--- a/src/OpenFOAM/algorithms/AABBTree/AABBTree.C
+++ b/src/OpenFOAM/algorithms/AABBTree/AABBTree.C
@@ -29,51 +29,8 @@ License
 #include "AABBTree.H"
 #include "bitSet.H"
 
-template<class Type>
-Foam::scalar Foam::AABBTree<Type>::tolerance_ = 1e-4;
-
 // * * * * * * * * * * * * * Protected Member Functions  * * * * * * * * * * //
 
-template<class Type>
-void Foam::AABBTree<Type>::writeOBJ
-(
-    const bool writeLinesOnly,
-    const treeBoundBox& bb,
-    label& vertI,
-    Ostream& os
-) const
-{
-    const pointField pts(bb.points());
-
-    for (const point& p : pts)
-    {
-        os << "v " << p.x() << ' ' << p.y() << ' ' << p.z() << nl;
-    }
-
-    if (writeLinesOnly)
-    {
-        for (const edge& e : treeBoundBox::edges)
-        {
-            os  << "l " << e[0] + vertI + 1 << ' ' << e[1] + vertI + 1 << nl;
-        }
-    }
-    else
-    {
-        for (const face& f : treeBoundBox::faces)
-        {
-            os  << 'f';
-            for (const label fpi : f)
-            {
-                os  << ' ' << fpi + vertI + 1;
-            }
-            os  << nl;
-        }
-    }
-
-    vertI += pts.size();
-}
-
-
 template<class Type>
 void Foam::AABBTree<Type>::writeOBJ
 (
@@ -89,7 +46,7 @@ void Foam::AABBTree<Type>::writeOBJ
 {
     if (!leavesOnly || nodeI < 0)
     {
-        writeOBJ(writeLinesOnly, bb, vertI, os);
+        AABBTreeBase::writeOBJ(os, bb, vertI, writeLinesOnly);
     }
 
     // recurse to find leaves
@@ -126,9 +83,9 @@ void Foam::AABBTree<Type>::createBoxes
 (
     const bool equalBinSize,
     const label level,
-    const List<Type>& objects,
+    const UList<Type>& objects,
     const pointField& points,
-    const DynamicList<label>& objectIDs,
+    const labelUList& objectIDs,
     const treeBoundBox& bb,
     const label nodeI,
 
@@ -153,7 +110,7 @@ void Foam::AABBTree<Type>::createBoxes
     }
 
 
-    scalar divide;
+    scalar pivotValue;
 
     if (equalBinSize)
     {
@@ -179,17 +136,17 @@ void Foam::AABBTree<Type>::createBoxes
 
         Foam::sort(component);
 
-        divide = component[component.size()/2];
+        pivotValue = component[component.size()/2];
     }
     else
     {
         // Geometric middle
-        divide = bb.min()[maxDir] + 0.5*maxSpan;
+        pivotValue = bb.min()[maxDir] + 0.5*maxSpan;
     }
 
 
-    scalar divMin = divide + tolerance_*maxSpan;
-    scalar divMax = divide - tolerance_*maxSpan;
+    const scalar divMin = pivotValue + tolerance_*maxSpan;
+    const scalar divMax = pivotValue - tolerance_*maxSpan;
 
 
     // Assign the objects to min or max bin
@@ -333,8 +290,8 @@ Foam::AABBTree<Type>::AABBTree
     const UList<Type>& objects,
     const pointField& points,
     const bool equalBinSize,
-    const label maxLevel,
-    const label minLeafSize
+    label maxLevel,
+    label minLeafSize
 )
 :
     maxLevel_(maxLevel),
@@ -356,7 +313,7 @@ Foam::AABBTree<Type>::AABBTree
     treeBoundBox topBb(points);
     topBb.inflate(0.01);
 
-    DynamicList<label> objectIDs(identity(objects.size()));
+    labelList objectIDs(identity(objects.size()));
 
     createBoxes
     (
@@ -438,16 +395,15 @@ Foam::AABBTree<Type>::AABBTree
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
 template<class Type>
-const Foam::List<Foam::treeBoundBox>& Foam::AABBTree<Type>::boundBoxes() const
+void Foam::AABBTree<Type>::writeOBJ(Ostream& os) const
 {
-    return boundBoxes_;
-}
+    label vertIndex(0);
 
-
-template<class Type>
-const Foam::List<Foam::labelList>& Foam::AABBTree<Type>::addressing() const
-{
-    return addressing_;
+    for (const treeBoundBox& bb : boundBoxes_)
+    {
+        // writeLinesOnly=false
+        AABBTreeBase::writeOBJ(os, bb, vertIndex, false);
+    }
 }
 
 
@@ -486,24 +442,7 @@ bool Foam::AABBTree<Type>::overlaps(const boundBox& bbIn) const
 template<class Type>
 Foam::Ostream& Foam::operator<<(Ostream& os, const AABBTree<Type>& tree)
 {
-    if (os.format() == IOstreamOption::ASCII)
-    {
-        os  << tree.maxLevel_ << token::SPACE
-            << tree.minLeafSize_ << token::SPACE
-            << tree.boundBoxes_ << token::SPACE
-            << tree.addressing_ << token::SPACE;
-    }
-    else
-    {
-        os.write
-        (
-            reinterpret_cast<const char*>(&tree.maxLevel_),
-            sizeof(tree.maxLevel_)
-          + sizeof(tree.minLeafSize_)
-        );
-        os  << tree.boundBoxes_
-            << tree.addressing_;
-    }
+    os  << tree.boundBoxes_ << tree.addressing_;
 
     os.check(FUNCTION_NAME);
     return os;
@@ -513,23 +452,7 @@ Foam::Ostream& Foam::operator<<(Ostream& os, const AABBTree<Type>& tree)
 template<class Type>
 Foam::Istream& Foam::operator>>(Istream& is, AABBTree<Type>& tree)
 {
-    if (is.format() == IOstreamOption::ASCII)
-    {
-        is  >> tree.maxLevel_
-            >> tree.minLeafSize_;
-    }
-    else
-    {
-        is.beginRawRead();
-
-        readRawLabel(is, &tree.maxLevel_);
-        readRawLabel(is, &tree.minLeafSize_);
-
-        is.endRawRead();
-    }
-
-    is  >> tree.boundBoxes_
-        >> tree.addressing_;
+    is  >> tree.boundBoxes_ >> tree.addressing_;
 
     is.check(FUNCTION_NAME);
     return is;
diff --git a/src/OpenFOAM/algorithms/AABBTree/AABBTree.H b/src/OpenFOAM/algorithms/AABBTree/AABBTree.H
index 1cfa78b819..f04ebbeb89 100644
--- a/src/OpenFOAM/algorithms/AABBTree/AABBTree.H
+++ b/src/OpenFOAM/algorithms/AABBTree/AABBTree.H
@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2015 OpenFOAM Foundation
+    Copyright (C) 2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -36,11 +37,12 @@ Description
 
 SourceFiles
     AABBTree.C
+    AABBTreeBase.C
 
 \*---------------------------------------------------------------------------*/
 
-#ifndef AABBTree_H
-#define AABBTree_H
+#ifndef Foam_AABBTree_H
+#define Foam_AABBTree_H
 
 #include "labelList.H"
 #include "labelPair.H"
@@ -54,10 +56,8 @@ SourceFiles
 namespace Foam
 {
 
-// Forward declaration of friend functions and operators
-
-template<class Type>
-class AABBTree;
+// Forward Declarations
+template<class Type> class AABBTree;
 
 template<class Type>
 Istream& operator>>(Istream&, AABBTree<Type>&);
@@ -65,21 +65,56 @@ Istream& operator>>(Istream&, AABBTree<Type>&);
 template<class Type>
 Ostream& operator<<(Ostream&, const AABBTree<Type>&);
 
+
+/*---------------------------------------------------------------------------*\
+                        Class AABBTreeBase Declaration
+\*---------------------------------------------------------------------------*/
+
+//- Template invariant parts for AABBTree
+class AABBTreeBase
+{
+protected:
+
+    // Static Data
+
+        //- Relative tolerance.
+        static scalar tolerance_;
+
+
+public:
+
+    // Constructors
+
+        //- Default construct
+        AABBTreeBase() = default;
+
+
+    // Output Helpers
+
+        //- Write treeBoundBox in OBJ format
+        static void writeOBJ
+        (
+            Ostream& os,
+            const treeBoundBox& bb,
+            label& vertIndex,
+            const bool writeLinesOnly = false
+        );
+};
+
+
 /*---------------------------------------------------------------------------*\
                           Class AABBTree Declaration
 \*---------------------------------------------------------------------------*/
 
 template<class Type>
 class AABBTree
+:
+    public AABBTreeBase
 {
-
 protected:
 
     // Protected Data
 
-        //- Tolerance
-        static scalar tolerance_;
-
         //- Maximum tree level
         label maxLevel_;
 
@@ -95,15 +130,6 @@ protected:
 
     // Protected Member Functions
 
-        //- Write OBJ file of bounding box
-        void writeOBJ
-        (
-            const bool writeLinesOnly,
-            const treeBoundBox& bb,
-            label& vertI,
-            Ostream& os
-        ) const;
-
         //- Write OBJ for all bounding boxes
         void writeOBJ
         (
@@ -122,9 +148,9 @@ protected:
         (
             const bool equalBinSize,
             const label level,
-            const List<Type>& objects,
+            const UList<Type>& objects,
             const pointField& points,
-            const DynamicList<label>& objectIDs,
+            const labelUList& objectIDs,
             const treeBoundBox& bb,
             const label nodeI,
 
@@ -138,7 +164,7 @@ public:
 
     // Constructors
 
-        //- Null constructor
+        //- Default construct
         AABBTree();
 
         //- Construct from components
@@ -148,33 +174,44 @@ public:
             const UList<Type>& objects,
             const pointField& points,
             const bool equalBinSize = true,
-            const label maxLevel = 3,
-            const label minBinSize = 100
+            label maxLevel = 3,
+            label minBinSize = 100
         );
 
 
     // Public Member Functions
 
-        // Access
+    // Access
 
-            //- Return the bounding boxes making up the tree
-            const List<treeBoundBox>& boundBoxes() const;
+        //- Return the bounding boxes making up the tree
+        const List<treeBoundBox>& boundBoxes() const noexcept
+        {
+            return boundBoxes_;
+        }
 
-            //- Return the contents addressing
-            const List<labelList>& addressing() const;
+        //- Return the contents addressing
+        const List<labelList>& addressing() const noexcept
+        {
+            return addressing_;
+        }
 
 
-        // Evaluation
+    // Evaluation
 
-            //- Determine whether a point is inside the bounding boxes
-            bool pointInside(const point& pt) const;
+        //- Determine whether a point is inside the bounding boxes
+        bool pointInside(const point& pt) const;
 
-            //- Determine whether a bounding box overlaps the tree bounding
-            //- boxes
-            bool overlaps(const boundBox& bbIn) const;
+        //- Determine whether a bounding box overlaps the tree bounding boxes
+        bool overlaps(const boundBox& bbIn) const;
 
 
-    // IOstream operators
+    // Write
+
+        //- Write all tree boxes (leaves) in OBJ format
+        void writeOBJ(Ostream& os) const;
+
+
+    // IOstream Operators
 
         friend Istream& operator>> <Type>(Istream&, AABBTree&);
         friend Ostream& operator<< <Type>(Ostream&, const AABBTree&);
diff --git a/src/OpenFOAM/algorithms/AABBTree/AABBTreeBase.C b/src/OpenFOAM/algorithms/AABBTree/AABBTreeBase.C
new file mode 100644
index 0000000000..274978737e
--- /dev/null
+++ b/src/OpenFOAM/algorithms/AABBTree/AABBTreeBase.C
@@ -0,0 +1,81 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | www.openfoam.com
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+    Copyright (C) 2022 OpenCFD Ltd.
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM.
+
+    OpenFOAM is free software: you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+    for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
+
+\*---------------------------------------------------------------------------*/
+
+#include "AABBTree.H"
+#include "treeBoundBox.H"
+
+// * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //
+
+Foam::scalar Foam::AABBTreeBase::tolerance_ = 1e-4;
+
+
+// * * * * * * * * * * * * * Static Member Functions * * * * * * * * * * * * //
+
+void Foam::AABBTreeBase::writeOBJ
+(
+    Ostream& os,
+    const treeBoundBox& bb,
+    label& vertIndex,
+    const bool writeLinesOnly
+)
+{
+    // Annotate with '#box' which can be grep'd for later
+    os  << "#box" << nl;
+
+    pointField pts(bb.points());
+
+    for (const point& p : pts)
+    {
+        os  << "v " << p.x() << ' ' << p.y() << ' ' << p.z() << nl;
+    }
+
+    if (writeLinesOnly)
+    {
+        for (const edge& e : treeBoundBox::edges)
+        {
+            os  << "l " << e[0] + vertIndex + 1
+                << ' ' << e[1] + vertIndex + 1 << nl;
+        }
+    }
+    else
+    {
+        for (const face& f : treeBoundBox::faces)
+        {
+            os  << 'f';
+            for (const label fpi : f)
+            {
+                os  << ' ' << fpi + vertIndex + 1;
+            }
+            os  << nl;
+        }
+    }
+
+    vertIndex += pts.size();
+}
+
+
+// ************************************************************************* //
diff --git a/src/OpenFOAM/algorithms/dynamicIndexedOctree/dynamicIndexedOctree.C b/src/OpenFOAM/algorithms/dynamicIndexedOctree/dynamicIndexedOctree.C
index 6ea3cab7f7..505b8504fc 100644
--- a/src/OpenFOAM/algorithms/dynamicIndexedOctree/dynamicIndexedOctree.C
+++ b/src/OpenFOAM/algorithms/dynamicIndexedOctree/dynamicIndexedOctree.C
@@ -179,7 +179,7 @@ void Foam::dynamicIndexedOctree<Type>::divide
 
 
 template<class Type>
-typename Foam::dynamicIndexedOctree<Type>::node
+Foam::dynamicIndexedOctreeBase::node
 Foam::dynamicIndexedOctree<Type>::divide
 (
     const treeBoundBox& bb,
@@ -295,9 +295,9 @@ void Foam::dynamicIndexedOctree<Type>::recursiveSubDivision
 
         // Recursively divide the contents until maxLevels_ is
         // reached or the content sizes are less than minSize_
-        for (direction subOct = 0; subOct < 8; subOct++)
+        for (direction subOct = 0; subOct < node::nChildren; ++subOct)
         {
-            const labelBits& subNodeLabel = nod.subNodes_[subOct];
+            const labelBits subNodeLabel = nod.subNodes_[subOct];
 
             if (isContent(subNodeLabel))
             {
@@ -335,7 +335,7 @@ Foam::volumeType Foam::dynamicIndexedOctree<Type>::calcVolumeType
 
     volumeType myType = volumeType::UNKNOWN;
 
-    for (direction octant = 0; octant < nod.subNodes_.size(); octant++)
+    for (direction octant = 0; octant < node::nChildren; ++octant)
     {
         volumeType subType;
 
@@ -1027,7 +1027,7 @@ bool Foam::dynamicIndexedOctree<Type>::walkToParent
     // Find octant nodeI is in.
     parentOctant = 255;
 
-    for (direction i = 0; i < parentNode.subNodes_.size(); i++)
+    for (direction i = 0; i < node::nChildren; ++i)
     {
         labelBits index = parentNode.subNodes_[i];
 
@@ -1794,7 +1794,7 @@ void Foam::dynamicIndexedOctree<Type>::findBox
     const node& nod = nodes_[nodeI];
     const treeBoundBox& nodeBb = nod.bb_;
 
-    for (direction octant = 0; octant < nod.subNodes_.size(); octant++)
+    for (direction octant = 0; octant < node::nChildren; ++octant)
     {
         labelBits index = nod.subNodes_[octant];
 
@@ -1842,7 +1842,7 @@ void Foam::dynamicIndexedOctree<Type>::findSphere
     const node& nod = nodes_[nodeI];
     const treeBoundBox& nodeBb = nod.bb_;
 
-    for (direction octant = 0; octant < nod.subNodes_.size(); octant++)
+    for (direction octant = 0; octant < node::nChildren; ++octant)
     {
         labelBits index = nod.subNodes_[octant];
 
@@ -1910,7 +1910,7 @@ void Foam::dynamicIndexedOctree<Type>::findNear
             {
                 const node& nod2 = tree2.nodes()[tree2.getNode(index2)];
 
-                for (direction i2 = 0; i2 < nod2.subNodes_.size(); i2++)
+                for (direction i2 = 0; i2 < node::nChildren; ++i2)
                 {
                     labelBits subIndex2 = nod2.subNodes_[i2];
                     const treeBoundBox subBb2
@@ -1938,7 +1938,7 @@ void Foam::dynamicIndexedOctree<Type>::findNear
         else if (tree2.isContent(index2))
         {
             // index2 is leaf, index1 not yet.
-            for (direction i1 = 0; i1 < nod1.subNodes_.size(); i1++)
+            for (direction i1 = 0; i1 < node::nChildren; ++i1)
             {
                 labelBits subIndex1 = nod1.subNodes_[i1];
                 const treeBoundBox subBb1
@@ -1978,7 +1978,7 @@ void Foam::dynamicIndexedOctree<Type>::findNear
 
             if (bb2.overlaps(searchBox))
             {
-                for (direction i2 = 0; i2 < nod2.subNodes_.size(); i2++)
+                for (direction i2 = 0; i2 < node::nChildren; ++i2)
                 {
                     labelBits subIndex2 = nod2.subNodes_[i2];
                     const treeBoundBox subBb2
@@ -2067,7 +2067,7 @@ Foam::label Foam::dynamicIndexedOctree<Type>::countElements
 
         const node& nod = nodes_[nodeI];
 
-        for (direction octant = 0; octant < nod.subNodes_.size(); octant++)
+        for (direction octant = 0; octant < node::nChildren; ++octant)
         {
             nElems += countElements(nod.subNodes_[octant]);
         }
@@ -2085,6 +2085,43 @@ Foam::label Foam::dynamicIndexedOctree<Type>::countElements
 }
 
 
+template<class Type>
+void Foam::dynamicIndexedOctree<Type>::writeOBJ
+(
+    const label nodeI,
+    Ostream& os,
+    label& vertIndex,
+    const bool leavesOnly,
+    const bool writeLinesOnly
+) const
+{
+    const node& nod = nodes_[nodeI];
+    const treeBoundBox& bb = nod.bb_;
+
+    for (direction octant = 0; octant < node::nChildren; ++octant)
+    {
+        const treeBoundBox subBb(bb.subBbox(octant));
+
+        labelBits index = nod.subNodes_[octant];
+
+        if (isNode(index))
+        {
+            label subNodeI = getNode(index);
+
+            writeOBJ(subNodeI, os, vertIndex, leavesOnly, writeLinesOnly);
+        }
+        else if (isContent(index))
+        {
+            indexedOctreeBase::writeOBJ(os, subBb, vertIndex, writeLinesOnly);
+        }
+        else if (isEmpty(index) && !leavesOnly)
+        {
+            indexedOctreeBase::writeOBJ(os, subBb, vertIndex, writeLinesOnly);
+        }
+    }
+}
+
+
 template<class Type>
 void Foam::dynamicIndexedOctree<Type>::writeOBJ
 (
@@ -2092,11 +2129,6 @@ void Foam::dynamicIndexedOctree<Type>::writeOBJ
     const direction octant
 ) const
 {
-    OFstream str
-    (
-        "node" + Foam::name(nodeI) + "_octant" + Foam::name(octant) + ".obj"
-    );
-
     labelBits index = nodes_[nodeI].subNodes_[octant];
 
     treeBoundBox subBb;
@@ -2110,24 +2142,28 @@ void Foam::dynamicIndexedOctree<Type>::writeOBJ
         subBb = nodes_[nodeI].bb_.subBbox(octant);
     }
 
+    OFstream os
+    (
+        "node" + Foam::name(nodeI) + "_octant" + Foam::name(octant) + ".obj"
+    );
+
     Pout<< "dumpContentNode : writing node:" << nodeI << " octant:" << octant
-        << " to " << str.name() << endl;
+        << " to " << os.name() << endl;
 
-    // Dump bounding box
-    pointField bbPoints(subBb.points());
+    bool writeLinesOnly(false);
+    label vertIndex(0);
+    indexedOctreeBase::writeOBJ(os, subBb, vertIndex, writeLinesOnly);
+}
 
-    forAll(bbPoints, i)
+
+template<class Type>
+void Foam::dynamicIndexedOctree<Type>::writeOBJ(Ostream& os) const
+{
+    if (!nodes_.empty())
     {
-        const point& pt = bbPoints[i];
-
-        str<< "v " << pt.x() << ' ' << pt.y() << ' ' << pt.z() << endl;
-    }
-
-    forAll(treeBoundBox::edges, i)
-    {
-        const edge& e = treeBoundBox::edges[i];
-
-        str<< "l " << e[0] + 1 << ' ' << e[1] + 1 << nl;
+        label vertIndex(0);
+        // leavesOnly=true, writeLinesOnly=false
+        writeOBJ(0, os, vertIndex, true, false);
     }
 }
 
@@ -2456,7 +2492,7 @@ Foam::volumeType Foam::dynamicIndexedOctree<Type>::getVolumeType
                 }
             }
 
-            Pout<< "dynamicIndexedOctree<Type>::getVolumeType : "
+            Pout<< "dynamicIndexedOctree::getVolumeType : "
                 << " bb:" << bb()
                 << " nodes_:" << nodes_.size()
                 << " nodeTypes_:" << nodeTypes_.size()
@@ -2552,9 +2588,9 @@ bool Foam::dynamicIndexedOctree<Type>::insertIndex
 {
     bool shapeInserted = false;
 
-    for (direction octant = 0; octant < 8; octant++)
+    for (direction octant = 0; octant < node::nChildren; ++octant)
     {
-        const labelBits& subNodeLabel = nodes_[nodIndex].subNodes_[octant];
+        const labelBits subNodeLabel = nodes_[nodIndex].subNodes_[octant];
 
         if (isNode(subNodeLabel))
         {
@@ -2642,9 +2678,9 @@ Foam::label Foam::dynamicIndexedOctree<Type>::removeIndex
 {
     label totalContents = 0;
 
-    for (direction octant = 0; octant < 8; octant++)
+    for (direction octant = 0; octant < node::nChildren; ++octant)
     {
-        const labelBits& subNodeLabel = nodes_[nodIndex].subNodes_[octant];
+        const labelBits subNodeLabel = nodes_[nodIndex].subNodes_[octant];
 
         if (isNode(subNodeLabel))
         {
@@ -2731,7 +2767,7 @@ void Foam::dynamicIndexedOctree<Type>::print
         << "parent:" << nod.parent_ << nl
         << "n:" << countElements(nodePlusOctant(nodeI, 0)) << nl;
 
-    for (direction octant = 0; octant < nod.subNodes_.size(); octant++)
+    for (direction octant = 0; octant < node::nChildren; ++octant)
     {
         const treeBoundBox subBb(bb.subBbox(octant));
 
@@ -2798,7 +2834,7 @@ void Foam::dynamicIndexedOctree<Type>::writeTreeInfo() const
         nEntries += contents_[i]->size();
     }
 
-    Pout<< "indexedOctree<Type>::indexedOctree"
+    Pout<< "indexedOctree::indexedOctree"
         << " : finished construction of tree of:" << shapes().typeName
         << nl
         << "    bounding box:     " << this->bb() << nl
diff --git a/src/OpenFOAM/algorithms/dynamicIndexedOctree/dynamicIndexedOctree.H b/src/OpenFOAM/algorithms/dynamicIndexedOctree/dynamicIndexedOctree.H
index 308e87a6ac..03dac5c960 100644
--- a/src/OpenFOAM/algorithms/dynamicIndexedOctree/dynamicIndexedOctree.H
+++ b/src/OpenFOAM/algorithms/dynamicIndexedOctree/dynamicIndexedOctree.H
@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
+    Copyright (C) 2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -38,14 +39,8 @@ SourceFiles
 #ifndef Foam_dynamicIndexedOctree_H
 #define Foam_dynamicIndexedOctree_H
 
-#include "treeBoundBox.H"
-#include "pointIndexHit.H"
-#include "FixedList.H"
-#include "Ostream.H"
-#include "HashSet.H"
-#include "labelBits.H"
-#include "PackedList.H"
-#include "volumeType.H"
+#include "indexedOctree.H"
+#include "DynamicList.H"
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
@@ -55,22 +50,36 @@ namespace Foam
 typedef DynamicList<autoPtr<DynamicList<label>>> contentListList;
 
 // Forward Declarations
-template<class Type> class dynamicIndexedOctree;
-
-template<class Type> Ostream& operator<<
-(
-    Ostream&,
-    const dynamicIndexedOctree<Type>&
-);
-
 class Istream;
+template<class Type> class dynamicIndexedOctree;
+template<class Type>
+Ostream& operator<<(Ostream&, const dynamicIndexedOctree<Type>&);
 
 
 /*---------------------------------------------------------------------------*\
-                        Class dynamicIndexedOctreeName Declaration
+                  Class dynamicIndexedOctreeBase Declaration
 \*---------------------------------------------------------------------------*/
 
-TemplateName(dynamicIndexedOctree);
+//- Template invariant parts for dynamicIndexedOctree
+//  Same type of node bookkeeping as indexedOctree
+class dynamicIndexedOctreeBase
+:
+    public indexedOctreeBase
+{
+public:
+
+    //- Document that we are using the same types of node
+    using node = indexedOctreeBase::node;
+
+    //- Runtime type information
+    ClassName("dynamicIndexedOctree");
+
+
+    // Constructors
+
+        //- Default construct
+        dynamicIndexedOctreeBase() = default;
+};
 
 
 /*---------------------------------------------------------------------------*\
@@ -80,54 +89,8 @@ TemplateName(dynamicIndexedOctree);
 template<class Type>
 class dynamicIndexedOctree
 :
-    public dynamicIndexedOctreeName
+    public dynamicIndexedOctreeBase
 {
-public:
-
-    // Data types
-
-        //- Tree node. Has up pointer and down pointers.
-        class node
-        {
-        public:
-
-            //- Bounding box of this node
-            treeBoundBox bb_;
-
-            //- Parent node (index into nodes_ of tree)
-            label parent_;
-
-            //- IDs of the 8 nodes on all sides of the mid point
-            FixedList<labelBits, 8> subNodes_;
-
-            friend Ostream& operator<< (Ostream& os, const node& n)
-            {
-                return os << n.bb_ << token::SPACE
-                    << n.parent_ << token::SPACE << n.subNodes_;
-            }
-
-            friend Istream& operator>> (Istream& is, node& n)
-            {
-                return is >> n.bb_ >> n.parent_ >> n.subNodes_;
-            }
-
-            friend bool operator==(const node& a, const node& b)
-            {
-                return
-                    a.bb_ == b.bb_
-                 && a.parent_ == b.parent_
-                 && a.subNodes_ == b.subNodes_;
-            }
-
-            friend bool operator!=(const node& a, const node& b)
-            {
-                return !(a == b);
-            }
-        };
-
-
-private:
-
     // Static data
 
         //- Relative perturbation tolerance. Determines when point is
@@ -137,7 +100,7 @@ private:
         static scalar perturbTol_;
 
 
-    // Private data
+    // Private Data
 
         //- Underlying shapes for geometric queries.
         const Type shapes_;
@@ -361,42 +324,24 @@ private:
             );
 
 
-        // Other
+    // Other
 
-            //- Count number of elements on this and sublevels
-            label countElements(const labelBits index) const;
+        //- Count number of elements on this and sublevels
+        label countElements(const labelBits index) const;
 
-            //- Dump node+octant to an obj file
-            void writeOBJ(const label nodeI, const direction octant) const;
+        //- Write node treeBoundBoxes in OBJ format
+        void writeOBJ
+        (
+            const label nodeI,
+            Ostream& os,
+            label& vertIndex,
+            const bool leavesOnly,
+            const bool writeLinesOnly = false
+        ) const;
 
-            //- From index into contents_ to subNodes_ entry
-            static labelBits contentPlusOctant
-            (
-                const label i,
-                const direction octant
-            )
-            {
-                return labelBits(-i - 1, octant);
-            }
+        //- Dump node+octant to an obj file
+        void writeOBJ(const label nodeI, const direction octant) const;
 
-            //- From index into nodes_ to subNodes_ entry
-            static labelBits nodePlusOctant
-            (
-                const label i,
-                const direction octant
-            )
-            {
-                return labelBits(i + 1, octant);
-            }
-
-            //- From empty to subNodes_ entry
-            static labelBits emptyPlusOctant
-            (
-                const direction octant
-            )
-            {
-                return labelBits(0, octant);
-            }
 
 public:
 
@@ -426,79 +371,36 @@ public:
 
     // Member Functions
 
-        // Access
+    // Access
 
-            //- Reference to shape
-            const Type& shapes() const
+        //- Reference to shape
+        const Type& shapes() const noexcept { return shapes_; }
+
+        //- List of all nodes
+        const List<node>& nodes() const noexcept { return nodes_; }
+
+        //- List of all contents
+        //- (referenced by those nodes that are contents)
+        const contentListList& contents() const
+        {
+            return contents_;
+        }
+
+        //- Per node, per octant whether is fully inside/outside/mixed.
+        PackedList<2>& nodeTypes() const noexcept
+        {
+            return nodeTypes_;
+        }
+
+        //- Top bounding box
+        const treeBoundBox& bb() const
+        {
+            if (nodes_.empty())
             {
-                return shapes_;
-            }
-
-            //- List of all nodes
-            const List<node>& nodes() const
-            {
-                return nodes_;
-            }
-
-            //- List of all contents (referenced by those nodes that are
-            //  contents)
-            const contentListList& contents() const
-            {
-                return contents_;
-            }
-
-            //- Top bounding box
-            const treeBoundBox& bb() const
-            {
-                if (nodes_.empty())
-                {
-                    return treeBoundBox::null();
-                }
-                return nodes_[0].bb_;
-            }
-
-
-        // Conversions for entries in subNodes_.
-
-            static bool isContent(const labelBits i)
-            {
-                return i.val() < 0;
-            }
-
-            static bool isEmpty(const labelBits i)
-            {
-                return i.val() == 0;
-            }
-
-            static bool isNode(const labelBits i)
-            {
-                return i.val() > 0;
-            }
-
-            static label getContent(const labelBits i)
-            {
-                if (!isContent(i))
-                {
-                    FatalErrorInFunction
-                        << abort(FatalError);
-                }
-                return -i.val()-1;
-            }
-
-            static label getNode(const labelBits i)
-            {
-                if (!isNode(i))
-                {
-                    FatalErrorInFunction
-                        << abort(FatalError);
-                }
-                return i.val() - 1;
-            }
-
-            static direction getOctant(const labelBits i)
-            {
-                return i.bits();
+                return treeBoundBox::null();
             }
+            return nodes_[0].bb_;
+        }
 
 
         // Queries
@@ -629,20 +531,23 @@ public:
             label removeIndex(const label nodIndex, const label index);
 
 
-        // Write
+    // Write
 
-            //- Print tree. Either print all indices (printContent = true) or
-            //  just size of contents nodes.
-            void print
-            (
-                prefixOSstream&,
-                const bool printContents,
-                const label
-            ) const;
+        //- Write all tree boxes as OBJ format
+        void writeOBJ(Ostream& os) const;
 
-            bool write(Ostream& os) const;
+        //- Print tree. Either print all indices (printContent = true) or
+        //  just size of contents nodes.
+        void print
+        (
+            prefixOSstream&,
+            const bool printContents,
+            const label
+        ) const;
 
-            void writeTreeInfo() const;
+        bool write(Ostream& os) const;
+
+        void writeTreeInfo() const;
 
 
     // IOstream Operators
diff --git a/src/OpenFOAM/algorithms/dynamicIndexedOctree/dynamicIndexedOctreeName.C b/src/OpenFOAM/algorithms/dynamicIndexedOctree/dynamicIndexedOctreeBase.C
similarity index 96%
rename from src/OpenFOAM/algorithms/dynamicIndexedOctree/dynamicIndexedOctreeName.C
rename to src/OpenFOAM/algorithms/dynamicIndexedOctree/dynamicIndexedOctreeBase.C
index 9d8e916363..6e67363753 100644
--- a/src/OpenFOAM/algorithms/dynamicIndexedOctree/dynamicIndexedOctreeName.C
+++ b/src/OpenFOAM/algorithms/dynamicIndexedOctree/dynamicIndexedOctreeBase.C
@@ -31,7 +31,7 @@ License
 
 namespace Foam
 {
-defineTypeNameAndDebug(dynamicIndexedOctreeName, 0);
+    defineTypeNameAndDebug(dynamicIndexedOctreeBase, 0);
 }
 
 
diff --git a/src/OpenFOAM/algorithms/indexedOctree/indexedOctree.C b/src/OpenFOAM/algorithms/indexedOctree/indexedOctree.C
index 60a94b6495..bcb6d1301e 100644
--- a/src/OpenFOAM/algorithms/indexedOctree/indexedOctree.C
+++ b/src/OpenFOAM/algorithms/indexedOctree/indexedOctree.C
@@ -155,7 +155,7 @@ void Foam::indexedOctree<Type>::divide
 
 
 template<class Type>
-typename Foam::indexedOctree<Type>::node
+Foam::indexedOctreeBase::node
 Foam::indexedOctree<Type>::divide
 (
     const treeBoundBox& bb,
@@ -227,7 +227,7 @@ template<class Type>
 void Foam::indexedOctree<Type>::splitNodes
 (
     const label minSize,
-    DynamicList<indexedOctree<Type>::node>& nodes,
+    DynamicList<indexedOctreeBase::node>& nodes,
     DynamicList<labelList>& contents
 ) const
 {
@@ -238,12 +238,7 @@ void Foam::indexedOctree<Type>::splitNodes
     // moved so make sure not to keep any references!
     for (label nodeI = 0; nodeI < currentSize; nodeI++)
     {
-        for
-        (
-            direction octant = 0;
-            octant < nodes[nodeI].subNodes_.size();
-            octant++
-        )
+        for (direction octant = 0; octant < node::nChildren; ++octant)
         {
             labelBits index = nodes[nodeI].subNodes_[octant];
 
@@ -294,7 +289,7 @@ Foam::label Foam::indexedOctree<Type>::compactContents
 
     if (level < compactLevel)
     {
-        for (direction octant = 0; octant < nod.subNodes_.size(); octant++)
+        for (direction octant = 0; octant < node::nChildren; ++octant)
         {
             labelBits index = nod.subNodes_[octant];
 
@@ -316,7 +311,7 @@ Foam::label Foam::indexedOctree<Type>::compactContents
     else if (level == compactLevel)
     {
         // Compact all content on this level
-        for (direction octant = 0; octant < nod.subNodes_.size(); octant++)
+        for (direction octant = 0; octant < node::nChildren; ++octant)
         {
             labelBits index = nod.subNodes_[octant];
 
@@ -356,7 +351,7 @@ Foam::volumeType Foam::indexedOctree<Type>::calcVolumeType
 
     volumeType myType = volumeType::UNKNOWN;
 
-    for (direction octant = 0; octant < nod.subNodes_.size(); octant++)
+    for (direction octant = 0; octant < node::nChildren; ++octant)
     {
         volumeType subType;
 
@@ -1048,7 +1043,7 @@ bool Foam::indexedOctree<Type>::walkToParent
     // Find octant nodeI is in.
     parentOctant = 255;
 
-    for (direction i = 0; i < parentNode.subNodes_.size(); i++)
+    for (direction i = 0; i < node::nChildren; ++i)
     {
         labelBits index = parentNode.subNodes_[i];
 
@@ -1827,7 +1822,7 @@ void Foam::indexedOctree<Type>::findBox
     const node& nod = nodes_[nodeI];
     const treeBoundBox& nodeBb = nod.bb_;
 
-    for (direction octant = 0; octant < nod.subNodes_.size(); octant++)
+    for (direction octant = 0; octant < node::nChildren; ++octant)
     {
         labelBits index = nod.subNodes_[octant];
 
@@ -1875,7 +1870,7 @@ void Foam::indexedOctree<Type>::findSphere
     const node& nod = nodes_[nodeI];
     const treeBoundBox& nodeBb = nod.bb_;
 
-    for (direction octant = 0; octant < nod.subNodes_.size(); octant++)
+    for (direction octant = 0; octant < node::nChildren; ++octant)
     {
         labelBits index = nod.subNodes_[octant];
 
@@ -1943,7 +1938,7 @@ void Foam::indexedOctree<Type>::findNear
             {
                 const node& nod2 = tree2.nodes()[tree2.getNode(index2)];
 
-                for (direction i2 = 0; i2 < nod2.subNodes_.size(); i2++)
+                for (direction i2 = 0; i2 < node::nChildren; ++i2)
                 {
                     labelBits subIndex2 = nod2.subNodes_[i2];
                     const treeBoundBox subBb2
@@ -1971,7 +1966,7 @@ void Foam::indexedOctree<Type>::findNear
         else if (tree2.isContent(index2))
         {
             // index2 is leaf, index1 not yet.
-            for (direction i1 = 0; i1 < nod1.subNodes_.size(); i1++)
+            for (direction i1 = 0; i1 < node::nChildren; ++i1)
             {
                 labelBits subIndex1 = nod1.subNodes_[i1];
                 const treeBoundBox subBb1
@@ -2011,7 +2006,7 @@ void Foam::indexedOctree<Type>::findNear
 
             if (bb2.overlaps(searchBox))
             {
-                for (direction i2 = 0; i2 < nod2.subNodes_.size(); i2++)
+                for (direction i2 = 0; i2 < node::nChildren; ++i2)
                 {
                     labelBits subIndex2 = nod2.subNodes_[i2];
                     const treeBoundBox subBb2
@@ -2100,7 +2095,7 @@ Foam::label Foam::indexedOctree<Type>::countElements
 
         const node& nod = nodes_[nodeI];
 
-        for (direction octant = 0; octant < nod.subNodes_.size(); octant++)
+        for (direction octant = 0; octant < node::nChildren; ++octant)
         {
             nElems += countElements(nod.subNodes_[octant]);
         }
@@ -2118,6 +2113,43 @@ Foam::label Foam::indexedOctree<Type>::countElements
 }
 
 
+template<class Type>
+void Foam::indexedOctree<Type>::writeOBJ
+(
+    const label nodeI,
+    Ostream& os,
+    label& vertIndex,
+    const bool leavesOnly,
+    const bool writeLinesOnly
+) const
+{
+    const node& nod = nodes_[nodeI];
+    const treeBoundBox& bb = nod.bb_;
+
+    for (direction octant = 0; octant < node::nChildren; ++octant)
+    {
+        const treeBoundBox subBb(bb.subBbox(octant));
+
+        labelBits index = nod.subNodes_[octant];
+
+        if (isNode(index))
+        {
+            label subNodeI = getNode(index);
+
+            writeOBJ(subNodeI, os, vertIndex, leavesOnly, writeLinesOnly);
+        }
+        else if (isContent(index))
+        {
+            indexedOctreeBase::writeOBJ(os, subBb, vertIndex, writeLinesOnly);
+        }
+        else if (isEmpty(index) && !leavesOnly)
+        {
+            indexedOctreeBase::writeOBJ(os, subBb, vertIndex, writeLinesOnly);
+        }
+    }
+}
+
+
 template<class Type>
 void Foam::indexedOctree<Type>::writeOBJ
 (
@@ -2125,11 +2157,6 @@ void Foam::indexedOctree<Type>::writeOBJ
     const direction octant
 ) const
 {
-    OFstream str
-    (
-        "node" + Foam::name(nodeI) + "_octant" + Foam::name(octant) + ".obj"
-    );
-
     labelBits index = nodes_[nodeI].subNodes_[octant];
 
     treeBoundBox subBb;
@@ -2143,24 +2170,28 @@ void Foam::indexedOctree<Type>::writeOBJ
         subBb = nodes_[nodeI].bb_.subBbox(octant);
     }
 
+    OFstream os
+    (
+        "node" + Foam::name(nodeI) + "_octant" + Foam::name(octant) + ".obj"
+    );
+
     Pout<< "dumpContentNode : writing node:" << nodeI << " octant:" << octant
-        << " to " << str.name() << endl;
+        << " to " << os.name() << endl;
 
-    // Dump bounding box
-    pointField bbPoints(subBb.points());
+    bool writeLinesOnly(false);
+    label vertIndex(0);
+    indexedOctreeBase::writeOBJ(os, subBb, vertIndex, writeLinesOnly);
+}
 
-    forAll(bbPoints, i)
+
+template<class Type>
+void Foam::indexedOctree<Type>::writeOBJ(Ostream& os) const
+{
+    if (!nodes_.empty())
     {
-        const point& pt = bbPoints[i];
-
-        str<< "v " << pt.x() << ' ' << pt.y() << ' ' << pt.z() << endl;
-    }
-
-    forAll(treeBoundBox::edges, i)
-    {
-        const edge& e = treeBoundBox::edges[i];
-
-        str<< "l " << e[0] + 1 << ' ' << e[1] + 1 << nl;
+        label vertIndex(0);
+        // leavesOnly=true, writeLinesOnly=false
+        writeOBJ(0, os, vertIndex, true, false);
     }
 }
 
@@ -2210,7 +2241,7 @@ Foam::indexedOctree<Type>::indexedOctree
     int oldMemSize = 0;
     if (debug)
     {
-        Pout<< "indexedOctree<Type>::indexedOctree:" << nl
+        Pout<< "indexedOctree::indexedOctree:" << nl
             << "    shapes:" << shapes.size() << nl
             << "    bb:" << bb << nl
             << endl;
@@ -2241,24 +2272,28 @@ Foam::indexedOctree<Type>::indexedOctree
     {
         // Count number of references into shapes (i.e. contents)
         label nEntries = 0;
+        label minEntries = shapes.size();
         label maxEntries = 0;
-        forAll(contents, i)
+        for (const auto& subContents : contents)
         {
-            maxEntries = max(maxEntries, contents[i].size());
-            nEntries += contents[i].size();
+            const label num = subContents.size();
+
+            nEntries += num;
+            minEntries = min(minEntries, num);
+            maxEntries = max(maxEntries, num);
         }
 
         if (debug)
         {
-            Pout<< "indexedOctree<Type>::indexedOctree:" << nl
+            Pout<< "indexedOctree::indexedOctree:" << nl
                 << "    nLevels:" << nLevels << nl
-                << "    nEntries per treeLeaf:" << nEntries/contents.size()
-                << nl
-                << "    nEntries per shape (duplicity):"
-                << nEntries/shapes.size()
-                << nl
-                << "    max nEntries:" << maxEntries
-                << nl
+                << "    nEntries:" << nEntries << nl
+                << "    - min per leaf: " << minEntries << nl
+                << "    - max per leaf: " << maxEntries << nl
+                << "    - avg per leaf: "
+                << scalar(nEntries)/contents.size() << nl
+                << "    - per shape (duplicity): "
+                << scalar(nEntries)/shapes_.size() << nl
                 << endl;
         }
 
@@ -2334,17 +2369,20 @@ Foam::indexedOctree<Type>::indexedOctree
     if (debug)
     {
         label nEntries = 0;
+        label minEntries = shapes.size();
         label maxEntries = 0;
-        forAll(contents_, i)
+        for (const auto& subContents : contents_)
         {
-            maxEntries = max(maxEntries, contents_[i].size());
-            nEntries += contents_[i].size();
+            const label num = subContents.size();
+
+            nEntries += num;
+            minEntries = min(minEntries, num);
+            maxEntries = max(maxEntries, num);
         }
 
         label memSize = memInfo().size();
 
-
-        Pout<< "indexedOctree<Type>::indexedOctree"
+        Pout<< "indexedOctree::indexedOctree"
             << " : finished construction of tree of:" << shapes.typeName
             << nl
             << "    bb:" << this->bb() << nl
@@ -2352,13 +2390,13 @@ Foam::indexedOctree<Type>::indexedOctree
             << "    nLevels:" << nLevels << nl
             << "    treeNodes:" << nodes_.size() << nl
             << "    nEntries:" << nEntries << nl
-            << "        per treeLeaf:"
+            << "    - min per leaf:" << minEntries << nl
+            << "    - max per leaf:" << maxEntries << nl
+            << "    - avg per leaf:"
             << scalar(nEntries)/contents.size() << nl
-            << "        per shape (duplicity):"
+            << "    - per shape (duplicity):"
             << scalar(nEntries)/shapes.size() << nl
-            << "    max nEntries:" << maxEntries
-            << nl
-            << "    total memory:" << memSize-oldMemSize
+            << "    total memory:" << memSize-oldMemSize << nl
             << endl;
     }
 }
@@ -2740,7 +2778,7 @@ Foam::volumeType Foam::indexedOctree<Type>::getVolumeType
                 }
             }
 
-            Pout<< "indexedOctree<Type>::getVolumeType : "
+            Pout<< "indexedOctree::getVolumeType : "
                 << " bb:" << bb()
                 << " nodes_:" << nodes_.size()
                 << " nodeTypes_:" << nodeTypes_.size()
@@ -2803,7 +2841,7 @@ void Foam::indexedOctree<Type>::print
         << "parent:" << nod.parent_ << nl
         << "n:" << countElements(nodePlusOctant(nodeI, 0)) << nl;
 
-    for (direction octant = 0; octant < nod.subNodes_.size(); octant++)
+    for (direction octant = 0; octant < node::nChildren; ++octant)
     {
         const treeBoundBox subBb(bb.subBbox(octant));
 
diff --git a/src/OpenFOAM/algorithms/indexedOctree/indexedOctree.H b/src/OpenFOAM/algorithms/indexedOctree/indexedOctree.H
index db366e4d32..fbe726ccce 100644
--- a/src/OpenFOAM/algorithms/indexedOctree/indexedOctree.H
+++ b/src/OpenFOAM/algorithms/indexedOctree/indexedOctree.H
@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
+    Copyright (C) 2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -52,45 +53,61 @@ namespace Foam
 {
 
 // Forward Declarations
+class Istream;
 template<class Type> class indexedOctree;
 template<class Type> Ostream& operator<<(Ostream&, const indexedOctree<Type>&);
-class Istream;
 
 
 /*---------------------------------------------------------------------------*\
-                        Class indexedOctreeName Declaration
+                      Class indexedOctreeBase Declaration
 \*---------------------------------------------------------------------------*/
 
-TemplateName(indexedOctree);
-
-
-/*---------------------------------------------------------------------------*\
-                           Class indexedOctree Declaration
-\*---------------------------------------------------------------------------*/
-
-template<class Type>
-class indexedOctree
-:
-    public indexedOctreeName
+//- Template invariant parts for indexedOctree
+//  The internal node bookkeeping is encoded follows:
+//  - 0: empty
+//  - +ve: parent
+//  - -ve: leaf
+class indexedOctreeBase
 {
 public:
 
-    // Data types
+    // Public Data Types
 
         //- Tree node. Has up pointer and down pointers.
         class node
         {
         public:
 
+            //- Has exactly 8 sub-nodes (octants)
+            static constexpr direction nChildren = 8;
+
             //- Bounding box of this node
             treeBoundBox bb_;
 
-            //- Parent node (index into nodes_ of tree)
-            label parent_;
+            //- Parent node (index into flat list addressing for tree)
+            label parent_ = -1;
 
             //- IDs of the 8 nodes on all sides of the mid point
             FixedList<labelBits, 8> subNodes_;
 
+
+        // Operators
+
+            friend bool operator==(const node& a, const node& b)
+            {
+                return
+                (
+                    a.parent_ == b.parent_
+                 && a.subNodes_ == b.subNodes_
+                 && a.bb_ == b.bb_
+                );
+            }
+
+            friend bool operator!=(const node& a, const node& b)
+            {
+                return !(a == b);
+            }
+
             friend Ostream& operator<< (Ostream& os, const node& n)
             {
                 return os << n.bb_ << token::SPACE
@@ -101,24 +118,124 @@ public:
             {
                 return is >> n.bb_ >> n.parent_ >> n.subNodes_;
             }
-
-            friend bool operator==(const node& a, const node& b)
-            {
-                return
-                    a.bb_ == b.bb_
-                 && a.parent_ == b.parent_
-                 && a.subNodes_ == b.subNodes_;
-            }
-
-            friend bool operator!=(const node& a, const node& b)
-            {
-                return !(a == b);
-            }
         };
 
 
-private:
+    // Static Functions
 
+    // Tests for node handling
+    // (0: empty, +ve: parent, -ve: leaf)
+
+        //- An empty node - no content
+        static bool isEmpty(labelBits i) noexcept
+        {
+            return (i.val() == 0);
+        }
+
+        //- Node with content (leaf)
+        static bool isContent(labelBits i) noexcept
+        {
+            return (i.val() < 0);
+        }
+
+        //- A parent node
+        static bool isNode(labelBits i) noexcept
+        {
+            return (i.val() > 0);
+        }
+
+
+    // Decode/retrieve node addressing
+
+        //- Return real (dereferenced) index for a content node
+        static label getContent(labelBits i)
+        {
+            if (!isContent(i))
+            {
+                FatalErrorInFunction
+                    << abort(FatalError);
+            }
+            return (-i.val()-1);
+        }
+
+        //- Return real (dereferenced) index for a parent node
+        static label getNode(const labelBits i)
+        {
+            if (!isNode(i))
+            {
+                FatalErrorInFunction
+                    << abort(FatalError);
+            }
+            return (i.val()-1);
+        }
+
+        //- Return sub-node direction/octant
+        static direction getOctant(labelBits i) noexcept
+        {
+            return i.bits();
+        }
+
+
+protected:
+
+    // Protected Member Functions
+
+    // Encode node addressing
+    // (only used when building)
+
+        //- From empty to subNodes_ entry
+        static labelBits emptyPlusOctant(direction octant)
+        {
+            return labelBits(0, octant);
+        }
+
+        //- From index into contents_ to subNodes_ entry
+        static labelBits contentPlusOctant(label i, direction octant)
+        {
+            return labelBits(-i-1, octant);
+        }
+
+        //- From index into nodes_ to subNodes_ entry
+        static labelBits nodePlusOctant(label i, direction octant)
+        {
+            return labelBits(i+1, octant);
+        }
+
+
+public:
+
+    //- Runtime type information
+    ClassName("indexedOctree");
+
+
+    // Constructors
+
+        //- Default construct
+        indexedOctreeBase() = default;
+
+
+    // Output Helpers
+
+        //- Write treeBoundBox in OBJ format
+        static void writeOBJ
+        (
+            Ostream& os,
+            const treeBoundBox& bb,
+            label& vertIndex,
+            const bool writeLinesOnly = false
+        );
+};
+
+
+/*---------------------------------------------------------------------------*\
+                           Class indexedOctree Declaration
+\*---------------------------------------------------------------------------*/
+
+template<class Type>
+class indexedOctree
+:
+    public indexedOctreeBase
+{
     // Static data
 
         //- Relative perturbation tolerance. Determines when point is
@@ -128,7 +245,7 @@ private:
         static scalar perturbTol_;
 
 
-    // Private data
+    // Private Data
 
         //- Underlying shapes for geometric queries.
         const Type shapes_;
@@ -142,6 +259,7 @@ private:
         //- Per node per octant whether is fully inside/outside/mixed.
         mutable PackedList<2> nodeTypes_;
 
+
     // Private Member Functions
 
         //- Helper: does bb intersect a sphere around sample? Or is any
@@ -361,42 +479,24 @@ private:
             );
 
 
-        // Other
+    // Other
 
-            //- Count number of elements on this and sublevels
-            label countElements(const labelBits index) const;
+        //- Count number of elements on this and sublevels
+        label countElements(const labelBits index) const;
 
-            //- Dump node+octant to an obj file
-            void writeOBJ(const label nodeI, const direction octant) const;
+        //- Write node treeBoundBoxes in OBJ format
+        void writeOBJ
+        (
+            const label nodeI,
+            Ostream& os,
+            label& vertIndex,
+            const bool leavesOnly,
+            const bool writeLinesOnly = false
+        ) const;
 
-            //- From index into contents_ to subNodes_ entry
-            static labelBits contentPlusOctant
-            (
-                const label i,
-                const direction octant
-            )
-            {
-                return labelBits(-i - 1, octant);
-            }
+        //- Dump node+octant to an obj file
+        void writeOBJ(const label nodeI, const direction octant) const;
 
-            //- From index into nodes_ to subNodes_ entry
-            static labelBits nodePlusOctant
-            (
-                const label i,
-                const direction octant
-            )
-            {
-                return labelBits(i + 1, octant);
-            }
-
-            //- From empty to subNodes_ entry
-            static labelBits emptyPlusOctant
-            (
-                const direction octant
-            )
-            {
-                return labelBits(0, octant);
-            }
 
 public:
 
@@ -437,87 +537,39 @@ public:
             return autoPtr<indexedOctree<Type>>::New(*this);
         }
 
+
     // Member Functions
 
-        // Access
+    // Access
 
-            //- Reference to shape
-            const Type& shapes() const
+        //- Reference to shape
+        const Type& shapes() const noexcept { return shapes_; }
+
+        //- List of all nodes
+        const List<node>& nodes() const noexcept { return nodes_; }
+
+        //- List of all contents
+        //- (referenced by those nodes that are contents)
+        const List<labelList>& contents() const noexcept
+        {
+            return contents_;
+        }
+
+        //- Per node, per octant whether is fully inside/outside/mixed.
+        PackedList<2>& nodeTypes() const noexcept
+        {
+            return nodeTypes_;
+        }
+
+        //- Top bounding box
+        const treeBoundBox& bb() const
+        {
+            if (nodes_.empty())
             {
-                return shapes_;
-            }
-
-            //- List of all nodes
-            const List<node>& nodes() const
-            {
-                return nodes_;
-            }
-
-            //- List of all contents (referenced by those nodes that are
-            //  contents)
-            const labelListList& contents() const
-            {
-                return contents_;
-            }
-
-            //- Top bounding box
-            const treeBoundBox& bb() const
-            {
-                if (nodes_.empty())
-                {
-                    return treeBoundBox::null();
-                }
-                return nodes_[0].bb_;
-            }
-
-            //- Per node, per octant whether is fully inside/outside/mixed.
-            PackedList<2>& nodeTypes() const
-            {
-                return nodeTypes_;
-            }
-
-
-        // Conversions for entries in subNodes_.
-
-            static bool isContent(const labelBits i)
-            {
-                return i.val() < 0;
-            }
-
-            static bool isEmpty(const labelBits i)
-            {
-                return i.val() == 0;
-            }
-
-            static bool isNode(const labelBits i)
-            {
-                return i.val() > 0;
-            }
-
-            static label getContent(const labelBits i)
-            {
-                if (!isContent(i))
-                {
-                    FatalErrorInFunction
-                        << abort(FatalError);
-                }
-                return -i.val()-1;
-            }
-
-            static label getNode(const labelBits i)
-            {
-                if (!isNode(i))
-                {
-                    FatalErrorInFunction
-                        << abort(FatalError);
-                }
-                return i.val() - 1;
-            }
-
-            static direction getOctant(const labelBits i)
-            {
-                return i.bits();
+                return treeBoundBox::null();
             }
+            return nodes_[0].bb_;
+        }
 
 
         // Queries
@@ -670,18 +722,21 @@ public:
             ) const;
 
 
-        // Write
+    // Write
 
-            //- Print tree. Either print all indices (printContent = true) or
-            //  just size of contents nodes.
-            void print
-            (
-                prefixOSstream&,
-                const bool printContents,
-                const label
-            ) const;
+        //- Write (non-empty) tree boxes in OBJ format
+        void writeOBJ(Ostream& os) const;
 
-            bool write(Ostream& os) const;
+        //- Print tree. Either print all indices (printContent = true) or
+        //  just size of contents nodes.
+        void print
+        (
+            prefixOSstream&,
+            const bool printContents,
+            const label
+        ) const;
+
+        bool write(Ostream& os) const;
 
 
     // IOstream Operators
diff --git a/src/OpenFOAM/algorithms/indexedOctree/indexedOctreeName.C b/src/OpenFOAM/algorithms/indexedOctree/indexedOctreeBase.C
similarity index 58%
rename from src/OpenFOAM/algorithms/indexedOctree/indexedOctreeName.C
rename to src/OpenFOAM/algorithms/indexedOctree/indexedOctreeBase.C
index 3145fa96fa..416c39a8c7 100644
--- a/src/OpenFOAM/algorithms/indexedOctree/indexedOctreeName.C
+++ b/src/OpenFOAM/algorithms/indexedOctree/indexedOctreeBase.C
@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2012 OpenFOAM Foundation
+    Copyright (C) 2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -26,12 +27,58 @@ License
 \*---------------------------------------------------------------------------*/
 
 #include "indexedOctree.H"
+#include "treeBoundBox.H"
 
 // * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //
 
 namespace Foam
 {
-defineTypeNameAndDebug(indexedOctreeName, 0);
+    defineTypeNameAndDebug(indexedOctreeBase, 0);
+}
+
+
+// * * * * * * * * * * * * * Static Member Functions * * * * * * * * * * * * //
+
+void Foam::indexedOctreeBase::writeOBJ
+(
+    Ostream& os,
+    const treeBoundBox& bb,
+    label& vertIndex,
+    const bool writeLinesOnly
+)
+{
+    // Annotate with '#box' which can be grep'd for later
+    os  << "#box" << nl;
+
+    pointField pts(bb.points());
+
+    for (const point& p : pts)
+    {
+        os  << "v " << p.x() << ' ' << p.y() << ' ' << p.z() << nl;
+    }
+
+    if (writeLinesOnly)
+    {
+        for (const edge& e : treeBoundBox::edges)
+        {
+            os  << "l " << e[0] + vertIndex + 1
+                << ' ' << e[1] + vertIndex + 1 << nl;
+        }
+    }
+    else
+    {
+        for (const face& f : treeBoundBox::faces)
+        {
+            os  << 'f';
+            for (const label fpi : f)
+            {
+                os  << ' ' << fpi + vertIndex + 1;
+            }
+            os  << nl;
+        }
+    }
+
+    vertIndex += pts.size();
 }
 
 
diff --git a/src/parallel/distributed/distributedTriSurfaceMesh/distributedTriSurfaceMesh.C b/src/parallel/distributed/distributedTriSurfaceMesh/distributedTriSurfaceMesh.C
index 107be52c0b..8265d7b527 100644
--- a/src/parallel/distributed/distributedTriSurfaceMesh/distributedTriSurfaceMesh.C
+++ b/src/parallel/distributed/distributedTriSurfaceMesh/distributedTriSurfaceMesh.C
@@ -1517,7 +1517,7 @@ void Foam::distributedTriSurfaceMesh::collectLeafMids
     DynamicField<point>& midPoints
 ) const
 {
-    const indexedOctree<treeDataTriSurface>::node& nod = tree().nodes()[nodeI];
+    const auto& nod = tree().nodes()[nodeI];
 
     for (direction octant = 0; octant < nod.subNodes_.size(); octant++)
     {
@@ -1557,7 +1557,7 @@ Foam::volumeType Foam::distributedTriSurfaceMesh::calcVolumeType
     // Recurses to determine status of lowest level boxes. Level above is
     // combination of octants below.
 
-    const indexedOctree<treeDataTriSurface>::node& nod = tree().nodes()[nodeI];
+    const auto& nod = tree().nodes()[nodeI];
 
     volumeType myType = volumeType::UNKNOWN;
 
@@ -1619,7 +1619,7 @@ Foam::volumeType Foam::distributedTriSurfaceMesh::cachedVolumeType
     const point& sample
 ) const
 {
-    const indexedOctree<treeDataTriSurface>::node& nod = tree().nodes()[nodeI];
+    const auto& nod = tree().nodes()[nodeI];
 
     direction octant = nod.bb_.subOctant(sample);
 
@@ -4141,10 +4141,9 @@ void Foam::distributedTriSurfaceMesh::getVolumeType
         {
             // Get local tree
             const indexedOctree<treeDataTriSurface>& t = tree();
+            const auto& nodes = t.nodes();
             PackedList<2>& nt = t.nodeTypes();
-            const List<indexedOctree<treeDataTriSurface>::node>& nodes =
-                t.nodes();
-            nt.setSize(nodes.size());
+            nt.resize(nodes.size());
             nt = volumeType::UNKNOWN;
 
             // Collect midpoints