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diff --git a/OpenSim/Region/PhysicsModules/BulletS/BSPrimDisplaced.cs b/OpenSim/Region/PhysicsModules/BulletS/BSPrimDisplaced.cs
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+++ b/OpenSim/Region/PhysicsModules/BulletS/BSPrimDisplaced.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 copyright
+ *       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.Reflection;
+using System.Runtime.InteropServices;
+using OpenMetaverse;
+using OpenSim.Framework;
+using OpenSim.Region.Physics.Manager;
+
+using OMV = OpenMetaverse;
+
+namespace OpenSim.Region.Physics.BulletSPlugin
+{
+public class BSPrimDisplaced : BSPrim
+{
+    // The purpose of this subclass is to do any mapping between what the simulator thinks
+    //    the prim position and orientation is and what the physical position/orientation.
+    //    This difference happens because Bullet assumes the center-of-mass is the <0,0,0>
+    //    of the prim/linkset. The simulator, on the other hand, tracks the location of
+    //    the prim/linkset by the location of the root prim. So, if center-of-mass is anywhere
+    //    but the origin of the root prim, the physical origin is displaced from the simulator origin.
+    //
+    // This routine works by capturing ForcePosition and
+    //    adjusting the simulator values (being set) into the physical values.
+    //    The conversion is also done in the opposite direction (physical origin -> simulator origin).
+    //
+    // The updateParameter call is also captured and the values from the physics engine
+    //    are converted into simulator origin values before being passed to the base
+    //    class.
+
+    // PositionDisplacement is the vehicle relative distance from the root prim position to the center-of-mass.
+    public virtual OMV.Vector3 PositionDisplacement { get; set; }
+
+    public BSPrimDisplaced(uint localID, String primName, BSScene parent_scene, OMV.Vector3 pos, OMV.Vector3 size,
+                       OMV.Quaternion rotation, PrimitiveBaseShape pbs, bool pisPhysical)
+        : base(localID, primName, parent_scene, pos, size, rotation, pbs, pisPhysical)
+    {
+        ClearDisplacement();
+    }
+
+    // Clears any center-of-mass displacement introduced by linksets, etc.
+    // Does not clear the displacement set by the user.
+    public void ClearDisplacement()
+    {
+        if (UserSetCenterOfMassDisplacement.HasValue)
+            PositionDisplacement = (OMV.Vector3)UserSetCenterOfMassDisplacement;
+        else
+            PositionDisplacement = OMV.Vector3.Zero;
+    }
+
+    // Set this sets and computes the displacement from the passed prim to the center-of-mass.
+    // A user set value for center-of-mass overrides whatever might be passed in here.
+    // The displacement is in local coordinates (relative to root prim in linkset oriented coordinates).
+    // Returns the relative offset from the root position to the center-of-mass.
+    // Called at taint time.
+    public virtual Vector3 SetEffectiveCenterOfMassDisplacement(Vector3 centerOfMassDisplacement)
+    {
+        PhysScene.AssertInTaintTime("BSPrimDisplaced.SetEffectiveCenterOfMassDisplacement");
+        Vector3 comDisp;
+        if (UserSetCenterOfMassDisplacement.HasValue)
+            comDisp = (OMV.Vector3)UserSetCenterOfMassDisplacement;
+        else
+            comDisp = centerOfMassDisplacement;
+
+        // Eliminate any jitter caused be very slight differences in masses and positions
+        if (comDisp.ApproxEquals(Vector3.Zero, 0.01f) )
+            comDisp = Vector3.Zero;
+
+        DetailLog("{0},BSPrimDisplaced.SetEffectiveCenterOfMassDisplacement,userSet={1},comDisp={2}",
+                                    LocalID, UserSetCenterOfMassDisplacement.HasValue, comDisp);
+        if ( !comDisp.ApproxEquals(PositionDisplacement, 0.01f) )
+        {
+            // Displacement setting is changing.
+            // The relationship between the physical object and simulated object must be aligned.
+            PositionDisplacement = comDisp;
+            this.ForcePosition = RawPosition;
+        }
+
+        return PositionDisplacement;
+    }
+
+    // 'ForcePosition' is the one way to set the physical position of the body in the physics engine.
+    // Displace the simulator idea of position (center of root prim) to the physical position.
+    public override Vector3 ForcePosition
+    {
+        get {
+            OMV.Vector3 physPosition = PhysScene.PE.GetPosition(PhysBody);
+            if (PositionDisplacement != OMV.Vector3.Zero)
+            {
+                // If there is some displacement, return the physical position (center-of-mass)
+                //     location minus the displacement to give the center of the root prim.
+                OMV.Vector3 displacement = PositionDisplacement * ForceOrientation;
+                DetailLog("{0},BSPrimDisplaced.ForcePosition,get,physPos={1},disp={2},simPos={3}",
+                                LocalID, physPosition, displacement, physPosition - displacement);
+                physPosition -= displacement;
+            }
+            RawPosition = physPosition;
+            return physPosition;
+        }
+        set
+        {
+            if (PositionDisplacement != OMV.Vector3.Zero)
+            {
+                // This value is the simulator's idea of where the prim is: the center of the root prim
+                RawPosition = value;
+
+                // Move the passed root prim postion to the center-of-mass position and set in the physics engine.
+                OMV.Vector3 displacement = PositionDisplacement * RawOrientation;
+                OMV.Vector3 displacedPos = RawPosition + displacement;
+                DetailLog("{0},BSPrimDisplaced.ForcePosition,set,simPos={1},disp={2},physPos={3}",
+                                        LocalID, RawPosition, displacement, displacedPos);
+                if (PhysBody.HasPhysicalBody)
+                {
+                    PhysScene.PE.SetTranslation(PhysBody, displacedPos, RawOrientation);
+                    ActivateIfPhysical(false);
+                }
+            }
+            else
+            {
+                base.ForcePosition = value;
+            }
+        }
+    }
+
+    // These are also overridden by BSPrimLinkable if the prim can be part of a linkset
+    public override OMV.Vector3 CenterOfMass
+    {
+        get { return RawPosition; }
+    }
+
+    public override OMV.Vector3 GeometricCenter
+    {
+        get { return RawPosition; }
+    }
+
+    public override void UpdateProperties(EntityProperties entprop)
+    {
+        // Undo any center-of-mass displacement that might have been done.
+        if (PositionDisplacement != OMV.Vector3.Zero)
+        {
+            // The origional shape was offset from 'zero' by PositionDisplacement.
+            // These physical location must be back converted to be centered around the displaced
+            //     root shape.
+
+            // Move the returned center-of-mass location to the root prim location.
+            OMV.Vector3 displacement = PositionDisplacement * entprop.Rotation;
+            OMV.Vector3 displacedPos = entprop.Position - displacement;
+            DetailLog("{0},BSPrimDisplaced.UpdateProperties,physPos={1},disp={2},simPos={3}",
+                                    LocalID, entprop.Position, displacement, displacedPos);
+            entprop.Position = displacedPos;
+        }
+
+        base.UpdateProperties(entprop);
+    }
+}
+}