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diff --git a/OpenSim/Region/Physics/BulletSNPlugin/BSLinkset.cs b/OpenSim/Region/Physics/BulletSNPlugin/BSLinkset.cs
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+/*
+ * Copyright (c) Contributors, http://opensimulator.org/
+ * See CONTRIBUTORS.TXT for a full list of copyright holders.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above copyrightD
+ *       notice, this list of conditions and the following disclaimer in the
+ *       documentation and/or other materials provided with the distribution.
+ *     * Neither the name of the OpenSimulator Project nor the
+ *       names of its contributors may be used to endorse or promote products
+ *       derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+using OMV = OpenMetaverse;
+
+namespace OpenSim.Region.Physics.BulletSNPlugin
+{
+
+// A BSPrim can get individual information about its linkedness attached
+//    to it through an instance of a subclass of LinksetInfo.
+// Each type of linkset will define the information needed for its type.
+public abstract class BSLinksetInfo
+{
+    public virtual void Clear() { }
+}
+
+public abstract class BSLinkset
+{
+    // private static string LogHeader = "[BULLETSIM LINKSET]";
+
+    public enum LinksetImplementation
+    {
+        Constraint   = 0,   // linkset tied together with constraints
+        Compound     = 1,   // linkset tied together as a compound object
+        Manual       = 2    // linkset tied together manually (code moves all the pieces)
+    }
+    // Create the correct type of linkset for this child
+    public static BSLinkset Factory(BSScene physScene, BSPhysObject parent)
+    {
+        BSLinkset ret = null;
+
+        switch ((int)BSParam.LinksetImplementation)
+        {
+            case (int)LinksetImplementation.Constraint:
+                ret = new BSLinksetConstraints(physScene, parent);
+                break;
+            case (int)LinksetImplementation.Compound:
+                ret = new BSLinksetCompound(physScene, parent);
+                break;
+            case (int)LinksetImplementation.Manual:
+                // ret = new BSLinksetManual(physScene, parent);
+                break;
+            default:
+                ret = new BSLinksetCompound(physScene, parent);
+                break;
+        }
+        return ret;
+    }
+
+    public BSPhysObject LinksetRoot { get; protected set; }
+
+    public BSScene PhysicsScene { get; private set; }
+
+    static int m_nextLinksetID = 1;
+    public int LinksetID { get; private set; }
+
+    // The children under the root in this linkset.
+    protected HashSet<BSPhysObject> m_children;
+
+    // We lock the diddling of linkset classes to prevent any badness.
+    // This locks the modification of the instances of this class. Changes
+    //    to the physical representation is done via the tainting mechenism.
+    protected object m_linksetActivityLock = new Object();
+
+    // Some linksets have a preferred physical shape.
+    // Returns SHAPE_UNKNOWN if there is no preference. Causes the correct shape to be selected.
+    public virtual BSPhysicsShapeType PreferredPhysicalShape(BSPhysObject requestor)
+    {
+        return BSPhysicsShapeType.SHAPE_UNKNOWN;
+    }
+
+    // We keep the prim's mass in the linkset structure since it could be dependent on other prims
+    protected float m_mass;
+    public float LinksetMass
+    {
+        get
+        {
+            return m_mass;
+        }
+    }
+
+    public virtual bool LinksetIsColliding { get { return false; } }
+
+    public OMV.Vector3 CenterOfMass
+    {
+        get { return ComputeLinksetCenterOfMass(); }
+    }
+
+    public OMV.Vector3 GeometricCenter
+    {
+        get { return ComputeLinksetGeometricCenter(); }
+    }
+
+    protected BSLinkset(BSScene scene, BSPhysObject parent)
+    {
+        // A simple linkset of one (no children)
+        LinksetID = m_nextLinksetID++;
+        // We create LOTS of linksets.
+        if (m_nextLinksetID <= 0)
+            m_nextLinksetID = 1;
+        PhysicsScene = scene;
+        LinksetRoot = parent;
+        m_children = new HashSet<BSPhysObject>();
+        m_mass = parent.RawMass;
+        Rebuilding = false;
+    }
+
+    // Link to a linkset where the child knows the parent.
+    // Parent changing should not happen so do some sanity checking.
+    // We return the parent's linkset so the child can track its membership.
+    // Called at runtime.
+    public BSLinkset AddMeToLinkset(BSPhysObject child)
+    {
+        lock (m_linksetActivityLock)
+        {
+            // Don't add the root to its own linkset
+            if (!IsRoot(child))
+                AddChildToLinkset(child);
+            m_mass = ComputeLinksetMass();
+        }
+        return this;
+    }
+
+    // Remove a child from a linkset.
+    // Returns a new linkset for the child which is a linkset of one (just the
+    //    orphened child).
+    // Called at runtime.
+    public BSLinkset RemoveMeFromLinkset(BSPhysObject child)
+    {
+        lock (m_linksetActivityLock)
+        {
+            if (IsRoot(child))
+            {
+                // Cannot remove the root from a linkset.
+                return this;
+            }
+            RemoveChildFromLinkset(child);
+            m_mass = ComputeLinksetMass();
+        }
+
+        // The child is down to a linkset of just itself
+        return BSLinkset.Factory(PhysicsScene, child);
+    }
+
+    // Return 'true' if the passed object is the root object of this linkset
+    public bool IsRoot(BSPhysObject requestor)
+    {
+        return (requestor.LocalID == LinksetRoot.LocalID);
+    }
+
+    public int NumberOfChildren { get { return m_children.Count; } }
+
+    // Return 'true' if this linkset has any children (more than the root member)
+    public bool HasAnyChildren { get { return (m_children.Count > 0); } }
+
+    // Return 'true' if this child is in this linkset
+    public bool HasChild(BSPhysObject child)
+    {
+        bool ret = false;
+        lock (m_linksetActivityLock)
+        {
+            ret = m_children.Contains(child);
+            /* Safer version but the above should work
+            foreach (BSPhysObject bp in m_children)
+            {
+                if (child.LocalID == bp.LocalID)
+                {
+                    ret = true;
+                    break;
+                }
+            }
+             */
+        }
+        return ret;
+    }
+
+    // Perform an action on each member of the linkset including root prim.
+    // Depends on the action on whether this should be done at taint time.
+    public delegate bool ForEachMemberAction(BSPhysObject obj);
+    public virtual bool ForEachMember(ForEachMemberAction action)
+    {
+        bool ret = false;
+        lock (m_linksetActivityLock)
+        {
+            action(LinksetRoot);
+            foreach (BSPhysObject po in m_children)
+            {
+                if (action(po))
+                    break;
+            }
+        }
+        return ret;
+    }
+
+    // I am the root of a linkset and a new child is being added
+    // Called while LinkActivity is locked.
+    protected abstract void AddChildToLinkset(BSPhysObject child);
+    
+    // I am the root of a linkset and one of my children is being removed.
+    // Safe to call even if the child is not really in my linkset.
+    protected abstract void RemoveChildFromLinkset(BSPhysObject child);
+
+    // When physical properties are changed the linkset needs to recalculate
+    //   its internal properties.
+    // May be called at runtime or taint-time.
+    public abstract void Refresh(BSPhysObject requestor);
+
+    // Flag denoting the linkset is in the process of being rebuilt.
+    // Used to know not the schedule a rebuild in the middle of a rebuild.
+    protected bool Rebuilding { get; set; }
+
+    // The object is going dynamic (physical). Do any setup necessary
+    //     for a dynamic linkset.
+    // Only the state of the passed object can be modified. The rest of the linkset
+    //     has not yet been fully constructed.
+    // Return 'true' if any properties updated on the passed object.
+    // Called at taint-time!
+    public abstract bool MakeDynamic(BSPhysObject child);
+
+    // The object is going static (non-physical). Do any setup necessary
+    //     for a static linkset.
+    // Return 'true' if any properties updated on the passed object.
+    // Called at taint-time!
+    public abstract bool MakeStatic(BSPhysObject child);
+
+    // Called when a parameter update comes from the physics engine for any object
+    //      of the linkset is received.
+    // Passed flag is update came from physics engine (true) or the user (false).
+    // Called at taint-time!!
+    public abstract void UpdateProperties(BSPhysObject physObject, bool physicalUpdate);
+
+    // Routine used when rebuilding the body of the root of the linkset
+    // Destroy all the constraints have have been made to root.
+    // This is called when the root body is changing.
+    // Returns 'true' of something was actually removed and would need restoring
+    // Called at taint-time!!
+    public abstract bool RemoveBodyDependencies(BSPrim child);
+
+    // Companion to RemoveBodyDependencies(). If RemoveBodyDependencies() returns 'true',
+    //     this routine will restore the removed constraints.
+    // Called at taint-time!!
+    public abstract void RestoreBodyDependencies(BSPrim child);
+
+    // ================================================================
+    protected virtual float ComputeLinksetMass()
+    {
+        float mass = LinksetRoot.RawMass;
+        if (HasAnyChildren)
+        {
+            lock (m_linksetActivityLock)
+            {
+                foreach (BSPhysObject bp in m_children)
+                {
+                    mass += bp.RawMass;
+                }
+            }
+        }
+        return mass;
+    }
+
+    protected virtual OMV.Vector3 ComputeLinksetCenterOfMass()
+    {
+        OMV.Vector3 com;
+        lock (m_linksetActivityLock)
+        {
+            com = LinksetRoot.Position * LinksetRoot.RawMass;
+            float totalMass = LinksetRoot.RawMass;
+
+            foreach (BSPhysObject bp in m_children)
+            {
+                com += bp.Position * bp.RawMass;
+                totalMass += bp.RawMass;
+            }
+            if (totalMass != 0f)
+                com /= totalMass;
+        }
+
+        return com;
+    }
+
+    protected virtual OMV.Vector3 ComputeLinksetGeometricCenter()
+    {
+        OMV.Vector3 com;
+        lock (m_linksetActivityLock)
+        {
+            com = LinksetRoot.Position;
+
+            foreach (BSPhysObject bp in m_children)
+            {
+                com += bp.Position * bp.RawMass;
+            }
+            com /= (m_children.Count + 1);
+        }
+
+        return com;
+    }
+
+    // Invoke the detailed logger and output something if it's enabled.
+    protected void DetailLog(string msg, params Object[] args)
+    {
+        if (PhysicsScene.PhysicsLogging.Enabled)
+            PhysicsScene.DetailLog(msg, args);
+    }
+
+}
+}