12 files changed, 155 insertions, 38 deletions

diff --git a/OpenSim/Region/Physics/BulletSPlugin/BSCharacter.cs b/OpenSim/Region/Physics/BulletSPlugin/BSCharacter.cs
index 21aa9be..88460cc 100644
--- a/OpenSim/Region/Physics/BulletSPlugin/BSCharacter.cs
+++ b/OpenSim/Region/Physics/BulletSPlugin/BSCharacter.cs
@@ -124,7 +124,9 @@ public sealed class BSCharacter : BSPhysObject
         PhysicsScene.TaintedObject("BSCharacter.destroy", delegate()
         {
             PhysicsScene.Shapes.DereferenceBody(PhysBody, true, null);
+            PhysBody.Clear();
             PhysicsScene.Shapes.DereferenceShape(PhysShape, true, null);
+            PhysShape.Clear();
         });
     }
 
diff --git a/OpenSim/Region/Physics/BulletSPlugin/BSConstraint.cs b/OpenSim/Region/Physics/BulletSPlugin/BSConstraint.cs
index 65fac00..6b1e304 100755
--- a/OpenSim/Region/Physics/BulletSPlugin/BSConstraint.cs
+++ b/OpenSim/Region/Physics/BulletSPlugin/BSConstraint.cs
@@ -57,7 +57,7 @@ public abstract class BSConstraint : IDisposable
         if (m_enabled)
         {
             m_enabled = false;
-            if (m_constraint.ptr != IntPtr.Zero)
+            if (m_constraint.HasPhysicalConstraint)
             {
                 bool success = BulletSimAPI.DestroyConstraint2(m_world.ptr, m_constraint.ptr);
                 m_world.physicsScene.DetailLog("{0},BSConstraint.Dispose,taint,id1={1},body1={2},id2={3},body2={4},success={5}",
@@ -65,7 +65,7 @@ public abstract class BSConstraint : IDisposable
                                     m_body1.ID, m_body1.ptr.ToString("X"),
                                     m_body2.ID, m_body2.ptr.ToString("X"),
                                     success);
-                m_constraint.ptr = System.IntPtr.Zero;
+                m_constraint.Clear();
             }
         }
     }
diff --git a/OpenSim/Region/Physics/BulletSPlugin/BSConstraint6Dof.cs b/OpenSim/Region/Physics/BulletSPlugin/BSConstraint6Dof.cs
index 23ef052..b073555 100755
--- a/OpenSim/Region/Physics/BulletSPlugin/BSConstraint6Dof.cs
+++ b/OpenSim/Region/Physics/BulletSPlugin/BSConstraint6Dof.cs
@@ -65,7 +65,7 @@ public sealed class BSConstraint6Dof : BSConstraint
         m_world = world;
         m_body1 = obj1;
         m_body2 = obj2;
-        if (obj1.ptr == IntPtr.Zero || obj2.ptr == IntPtr.Zero)
+        if (!obj1.HasPhysicalBody || !obj2.HasPhysicalBody)
         {
             world.physicsScene.DetailLog("{0},BS6DOFConstraint,badBodyPtr,wID={1}, rID={2}, rBody={3}, cID={4}, cBody={5}",
                             BSScene.DetailLogZero, world.worldID,
@@ -83,7 +83,7 @@ public sealed class BSConstraint6Dof : BSConstraint
             world.physicsScene.DetailLog("{0},BS6DofConstraint,createMidPoint,wID={1}, csrt={2}, rID={3}, rBody={4}, cID={5}, cBody={6}",
                                 BSScene.DetailLogZero, world.worldID, m_constraint.ptr.ToString("X"),
                                 obj1.ID, obj1.ptr.ToString("X"), obj2.ID, obj2.ptr.ToString("X"));
-            if (m_constraint.ptr == IntPtr.Zero)
+            if (!m_constraint.HasPhysicalConstraint)
             {
                 world.physicsScene.Logger.ErrorFormat("{0} Failed creation of 6Dof constraint. rootID={1}, childID={2}",
                                 LogHeader, obj1.ID, obj2.ID);
diff --git a/OpenSim/Region/Physics/BulletSPlugin/BSLinkset.cs b/OpenSim/Region/Physics/BulletSPlugin/BSLinkset.cs
index 0df4310..777c5cb 100755
--- a/OpenSim/Region/Physics/BulletSPlugin/BSLinkset.cs
+++ b/OpenSim/Region/Physics/BulletSPlugin/BSLinkset.cs
@@ -32,6 +32,14 @@ using OMV = OpenMetaverse;
 
 namespace OpenSim.Region.Physics.BulletSPlugin
 {
+
+// 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 abstract class BSLinkset
 {
     // private static string LogHeader = "[BULLETSIM LINKSET]";
diff --git a/OpenSim/Region/Physics/BulletSPlugin/BSLinksetCompound.cs b/OpenSim/Region/Physics/BulletSPlugin/BSLinksetCompound.cs
index bc9f9be..fe5b5e3 100755
--- a/OpenSim/Region/Physics/BulletSPlugin/BSLinksetCompound.cs
+++ b/OpenSim/Region/Physics/BulletSPlugin/BSLinksetCompound.cs
@@ -32,6 +32,31 @@ using OMV = OpenMetaverse;
 
 namespace OpenSim.Region.Physics.BulletSPlugin
 {
+
+// When a child is linked, the relationship position of the child to the parent
+//    is remembered so the child's world position can be recomputed when it is
+//    removed from the linkset.
+sealed class BSLinksetCompoundInfo : BSLinksetInfo
+{
+    public OMV.Vector3 OffsetPos;
+    public OMV.Quaternion OffsetRot;
+    public BSLinksetCompoundInfo(OMV.Vector3 p, OMV.Quaternion r)
+    {
+        OffsetPos = p;
+        OffsetRot = r;
+    }
+    public override string ToString()
+    {
+        StringBuilder buff = new StringBuilder();
+        buff.Append("<p=");
+        buff.Append(OffsetPos.ToString());
+        buff.Append(",r=");
+        buff.Append(OffsetRot.ToString());
+        buff.Append(">");
+        return buff.ToString();
+    }
+};
+
 public sealed class BSLinksetCompound : BSLinkset
 {
     private static string LogHeader = "[BULLETSIM LINKSET COMPOUND]";
@@ -44,6 +69,7 @@ public sealed class BSLinksetCompound : BSLinkset
     // For compound implimented linksets, if there are children, use compound shape for the root.
     public override BSPhysicsShapeType PreferredPhysicalShape(BSPhysObject requestor)
     { 
+        // Returning 'unknown' means we don't have a preference.
         BSPhysicsShapeType ret = BSPhysicsShapeType.SHAPE_UNKNOWN;
         if (IsRoot(requestor) && HasAnyChildren)
         {
@@ -63,10 +89,10 @@ public sealed class BSLinksetCompound : BSLinkset
         // InternalRefresh(requestor);
     }
 
+    // Schedule a refresh to happen after all the other taint processing.
     private void InternalRefresh(BSPhysObject requestor)
     {
         DetailLog("{0},BSLinksetCompound.Refresh,schedulingRefresh,requestor={1}", LinksetRoot.LocalID, requestor.LocalID);
-        // Queue to happen after all the other taint processing
         PhysicsScene.PostTaintObject("BSLinksetCompound.Refresh", requestor.LocalID, delegate()
         {
             if (IsRoot(requestor) && HasAnyChildren)
@@ -108,7 +134,7 @@ public sealed class BSLinksetCompound : BSLinkset
         {
             // The non-physical children can come back to life.
             BulletSimAPI.RemoveFromCollisionFlags2(child.PhysBody.ptr, CollisionFlags.CF_NO_CONTACT_RESPONSE);
-            // Don't force activation so setting of DISABLE_SIMULATION can stay.
+            // Don't force activation so setting of DISABLE_SIMULATION can stay if used.
             BulletSimAPI.Activate2(child.PhysBody.ptr, false);
             ret = true;
         }
@@ -146,6 +172,10 @@ public sealed class BSLinksetCompound : BSLinkset
 
         if (!IsRoot(child))
         {
+            // Because it is a convenient time, recompute child world position and rotation based on
+            //    its position in the linkset.
+            RecomputeChildWorldPosition(child, true);
+
             // Cause the current shape to be freed and the new one to be built.
             InternalRefresh(LinksetRoot);
             ret = true;
@@ -154,6 +184,42 @@ public sealed class BSLinksetCompound : BSLinkset
         return ret;
     }
 
+    // When the linkset is built, the child shape is added
+    //    to the compound shape relative to the root shape. The linkset then moves around but
+    //    this does not move the actual child prim. The child prim's location must be recomputed
+    //    based on the location of the root shape.
+    private void RecomputeChildWorldPosition(BSPhysObject child, bool inTaintTime)
+    {
+        BSLinksetCompoundInfo lci = child.LinksetInfo as BSLinksetCompoundInfo;
+        if (lci != null)
+        {
+            if (inTaintTime)
+            {
+                OMV.Vector3 oldPos = child.RawPosition;
+                child.ForcePosition = LinksetRoot.RawPosition + lci.OffsetPos;
+                child.ForceOrientation = LinksetRoot.RawOrientation * lci.OffsetRot;
+                DetailLog("{0},BSLinksetCompound.RecomputeChildWorldPosition,oldPos={1},lci={2},newPos={3}",
+                                            child.LocalID, oldPos, lci, child.RawPosition);
+            }
+            else
+            {
+                // TaintedObject is not used here so the raw position is set now and not at taint-time.
+                child.Position = LinksetRoot.RawPosition + lci.OffsetPos;
+                child.Orientation = LinksetRoot.RawOrientation * lci.OffsetRot;
+            }
+        }
+        else
+        {
+            // This happens when children have been added to the linkset but the linkset
+            //     has not been constructed yet. So like, at taint time, adding children to a linkset
+            //     and then changing properties of the children (makePhysical, for instance)
+            //     but the post-print action of actually rebuilding the linkset has not yet happened.
+            // PhysicsScene.Logger.WarnFormat("{0} Restoring linkset child position failed because of no relative position computed. ID={1}",
+            //                                 LogHeader, child.LocalID);
+            DetailLog("{0},BSLinksetCompound.recomputeChildWorldPosition,noRelativePositonInfo", child.LocalID);
+        }
+    }
+
     // Companion to RemoveBodyDependencies(). If RemoveBodyDependencies() returns 'true',
     // this routine will restore the removed constraints.
     // Called at taint-time!!
@@ -192,8 +258,7 @@ public sealed class BSLinksetCompound : BSLinkset
                             child.LocalID, child.PhysBody.ptr.ToString("X"));
 
             // Cause the child's body to be rebuilt and thus restored to normal operation
-            // TODO: position and rotation must be restored because the child could have moved
-            //    based on the linkset.
+            RecomputeChildWorldPosition(child, false);
             child.ForceBodyShapeRebuild(false);
 
             if (!HasAnyChildren)
@@ -228,43 +293,57 @@ public sealed class BSLinksetCompound : BSLinkset
         {
             if (!IsRoot(cPrim))
             {
-                // Each child position and rotation is given relative to the root.
-                OMV.Quaternion invRootOrientation = OMV.Quaternion.Inverse(LinksetRoot.RawOrientation);
-                OMV.Vector3 displacementPos = (cPrim.RawPosition - LinksetRoot.RawPosition) * invRootOrientation;
-                OMV.Quaternion displacementRot = cPrim.RawOrientation * invRootOrientation;
+                // Compute the displacement of the child from the root of the linkset.
+                // This info is saved in the child prim so the relationship does not
+                //    change over time and the new child position can be computed
+                //    when the linkset is being disassembled (the linkset may have moved).
+                BSLinksetCompoundInfo lci = cPrim.LinksetInfo as BSLinksetCompoundInfo;
+                if (lci == null)
+                {
+                    // Each child position and rotation is given relative to the root.
+                    OMV.Quaternion invRootOrientation = OMV.Quaternion.Inverse(LinksetRoot.RawOrientation);
+                    OMV.Vector3 displacementPos = (cPrim.RawPosition - LinksetRoot.RawPosition) * invRootOrientation;
+                    OMV.Quaternion displacementRot = cPrim.RawOrientation * invRootOrientation;
+
+                    // Save relative position for recomputing child's world position after moving linkset.
+                    lci = new BSLinksetCompoundInfo(displacementPos, displacementRot);
+                    cPrim.LinksetInfo = lci;
+                    DetailLog("{0},BSLinksetCompound.RecomputeLinksetCompound,creatingRelPos,lci={1}", cPrim.LocalID, lci);
+                }
 
                 DetailLog("{0},BSLinksetCompound.RecomputeLinksetCompound,addMemberToShape,mID={1},mShape={2},dispPos={3},dispRot={4}",
-                    LinksetRoot.LocalID, cPrim.LocalID, cPrim.PhysShape, displacementPos, displacementRot);
+                    LinksetRoot.LocalID, cPrim.LocalID, cPrim.PhysShape, lci.OffsetPos, lci.OffsetRot);
 
                 if (cPrim.PhysShape.isNativeShape)
                 {
-                    // A native shape is turning into a null collision shape because native
+                    // A native shape is turning into a hull collision shape because native
                     //    shapes are not shared so we have to hullify it so it will be tracked
                     //    and freed at the correct time. This also solves the scaling problem
                     //    (native shapes scaled but hull/meshes are assumed to not be).
+                    // TODO: decide of the native shape can just be used in the compound shape.
+                    //    Use call to CreateGeomNonSpecial().
                     BulletShape saveShape = cPrim.PhysShape;
-                    cPrim.PhysShape.ptr = IntPtr.Zero;  // Don't let the create free the child's shape
+                    cPrim.PhysShape.Clear();        // Don't let the create free the child's shape
+                    // PhysicsScene.Shapes.CreateGeomNonSpecial(true, cPrim, null);
                     PhysicsScene.Shapes.CreateGeomMeshOrHull(cPrim, null);
                     BulletShape newShape = cPrim.PhysShape;
                     cPrim.PhysShape = saveShape;
-                    BulletSimAPI.AddChildShapeToCompoundShape2(LinksetRoot.PhysShape.ptr, newShape.ptr, displacementPos, displacementRot);
+                    BulletSimAPI.AddChildShapeToCompoundShape2(LinksetRoot.PhysShape.ptr, newShape.ptr, lci.OffsetPos , lci.OffsetRot);
                 }
                 else
                 {
                     // For the shared shapes (meshes and hulls), just use the shape in the child.
+                    // The reference count added here will be decremented when the compound shape
+                    //     is destroyed in BSShapeCollection (the child shapes are looped over and dereferenced).
                     if (PhysicsScene.Shapes.ReferenceShape(cPrim.PhysShape))
                     {
                         PhysicsScene.Logger.ErrorFormat("{0} Rebuilt sharable shape when building linkset! Region={1}, primID={2}, shape={3}",
                                             LogHeader, PhysicsScene.RegionName, cPrim.LocalID, cPrim.PhysShape);
                     }
-                    BulletSimAPI.AddChildShapeToCompoundShape2(LinksetRoot.PhysShape.ptr, cPrim.PhysShape.ptr, displacementPos, displacementRot);
+                    BulletSimAPI.AddChildShapeToCompoundShape2(LinksetRoot.PhysShape.ptr, cPrim.PhysShape.ptr, lci.OffsetPos , lci.OffsetRot);
                 }
             }
 
-            // TODO: need to phantomize the child prims left behind.
-            //     Maybe just destroy the children bodies and shapes and have them rebuild on unlink.
-            //     Selection/deselection might cause way too many build/destructions esp. for LARGE linksets.
-
             return false;   // 'false' says to move onto the next child in the list
         });
 
diff --git a/OpenSim/Region/Physics/BulletSPlugin/BSPhysObject.cs b/OpenSim/Region/Physics/BulletSPlugin/BSPhysObject.cs
index b05d4ee..d2fc15c 100755
--- a/OpenSim/Region/Physics/BulletSPlugin/BSPhysObject.cs
+++ b/OpenSim/Region/Physics/BulletSPlugin/BSPhysObject.cs
@@ -75,6 +75,7 @@ public abstract class BSPhysObject : PhysicsActor
     public string TypeName { get; protected set; }
 
     public BSLinkset Linkset { get; set; }
+    public BSLinksetInfo LinksetInfo { get; set; }
 
     // Return the object mass without calculating it or having side effects
     public abstract float RawMass { get; }
@@ -253,7 +254,9 @@ public abstract class BSPhysObject : PhysicsActor
         SubscribedEventsMs = 0;
         PhysicsScene.TaintedObject(TypeName+".UnSubscribeEvents", delegate()
         {
-            CurrentCollisionFlags = BulletSimAPI.RemoveFromCollisionFlags2(PhysBody.ptr, CollisionFlags.BS_SUBSCRIBE_COLLISION_EVENTS);
+            // Make sure there is a body there because sometimes destruction happens in an un-ideal order.
+            if (PhysBody.HasPhysicalBody)
+                CurrentCollisionFlags = BulletSimAPI.RemoveFromCollisionFlags2(PhysBody.ptr, CollisionFlags.BS_SUBSCRIBE_COLLISION_EVENTS);
         });
     }
     // Return 'true' if the simulator wants collision events
diff --git a/OpenSim/Region/Physics/BulletSPlugin/BSPrim.cs b/OpenSim/Region/Physics/BulletSPlugin/BSPrim.cs
index 627393a..d1d100d 100644
--- a/OpenSim/Region/Physics/BulletSPlugin/BSPrim.cs
+++ b/OpenSim/Region/Physics/BulletSPlugin/BSPrim.cs
@@ -108,8 +108,8 @@ public sealed class BSPrim : BSPhysObject
         _mass = CalculateMass();
 
         // No body or shape yet
-        PhysBody = new BulletBody(LocalID, IntPtr.Zero);
-        PhysShape = new BulletShape(IntPtr.Zero);
+        PhysBody = new BulletBody(LocalID);
+        PhysShape = new BulletShape();
 
         DetailLog("{0},BSPrim.constructor,call", LocalID);
         // do the actual object creation at taint time
@@ -143,7 +143,9 @@ public sealed class BSPrim : BSPhysObject
             DetailLog("{0},BSPrim.Destroy,taint,", LocalID);
             // If there are physical body and shape, release my use of same.
             PhysicsScene.Shapes.DereferenceBody(PhysBody, true, null);
+            PhysBody.Clear();
             PhysicsScene.Shapes.DereferenceShape(PhysShape, true, null);
+            PhysShape.Clear();
         });
     }
 
diff --git a/OpenSim/Region/Physics/BulletSPlugin/BSShapeCollection.cs b/OpenSim/Region/Physics/BulletSPlugin/BSShapeCollection.cs
index 933f573..74b4371 100755
--- a/OpenSim/Region/Physics/BulletSPlugin/BSShapeCollection.cs
+++ b/OpenSim/Region/Physics/BulletSPlugin/BSShapeCollection.cs
@@ -149,7 +149,7 @@ public sealed class BSShapeCollection : IDisposable
     // Called when releasing use of a BSBody. BSShape is handled separately.
     public void DereferenceBody(BulletBody body, bool inTaintTime, BodyDestructionCallback bodyCallback )
     {
-        if (body.ptr == IntPtr.Zero)
+        if (!body.HasPhysicalBody)
             return;
 
         lock (m_collectionActivityLock)
@@ -243,12 +243,12 @@ public sealed class BSShapeCollection : IDisposable
     // Release the usage of a shape.
     public void DereferenceShape(BulletShape shape, bool inTaintTime, ShapeDestructionCallback shapeCallback)
     {
-        if (shape.ptr == IntPtr.Zero)
+        if (!shape.HasPhysicalShape)
             return;
 
         PhysicsScene.TaintedObject(inTaintTime, "BSShapeCollection.DereferenceShape", delegate()
         {
-            if (shape.ptr != IntPtr.Zero)
+            if (shape.HasPhysicalShape)
             {
                 if (shape.isNativeShape)
                 {
@@ -440,7 +440,7 @@ public sealed class BSShapeCollection : IDisposable
     }
 
     // Create a mesh/hull shape or a native shape if 'nativeShapePossible' is 'true'.
-    private bool CreateGeomNonSpecial(bool forceRebuild, BSPhysObject prim, ShapeDestructionCallback shapeCallback)
+    public bool CreateGeomNonSpecial(bool forceRebuild, BSPhysObject prim, ShapeDestructionCallback shapeCallback)
     {
         bool ret = false;
         bool haveShape = false;
@@ -573,7 +573,7 @@ public sealed class BSShapeCollection : IDisposable
             // Native shapes are scaled in Bullet so set the scaling to the size
             newShape = new BulletShape(BulletSimAPI.BuildNativeShape2(PhysicsScene.World.ptr, nativeShapeData), shapeType);
         }
-        if (newShape.ptr == IntPtr.Zero)
+        if (!newShape.HasPhysicalShape)
         {
             PhysicsScene.Logger.ErrorFormat("{0} BuildPhysicalNativeShape failed. ID={1}, shape={2}",
                                     LogHeader, prim.LocalID, shapeType);
@@ -590,7 +590,7 @@ public sealed class BSShapeCollection : IDisposable
     // Called at taint-time!
     private bool GetReferenceToMesh(BSPhysObject prim, ShapeDestructionCallback shapeCallback)
     {
-        BulletShape newShape = new BulletShape(IntPtr.Zero);
+        BulletShape newShape = new BulletShape();
 
         float lod;
         System.UInt64 newMeshKey = ComputeShapeKey(prim.Size, prim.BaseShape, out lod);
@@ -860,7 +860,7 @@ public sealed class BSShapeCollection : IDisposable
     private BulletShape VerifyMeshCreated(BulletShape newShape, BSPhysObject prim)
     {
         // If the shape was successfully created, nothing more to do
-        if (newShape.ptr != IntPtr.Zero)
+        if (newShape.HasPhysicalShape)
             return newShape;
 
         // If this mesh has an underlying asset and we have not failed getting it before, fetch the asset
@@ -919,7 +919,7 @@ public sealed class BSShapeCollection : IDisposable
         bool ret = false;
 
         // the mesh, hull or native shape must have already been created in Bullet
-        bool mustRebuild = (prim.PhysBody.ptr == IntPtr.Zero);
+        bool mustRebuild = !prim.PhysBody.HasPhysicalBody;
 
         // If there is an existing body, verify it's of an acceptable type.
         // If not a solid object, body is a GhostObject. Otherwise a RigidBody.
diff --git a/OpenSim/Region/Physics/BulletSPlugin/BSTerrainHeightmap.cs b/OpenSim/Region/Physics/BulletSPlugin/BSTerrainHeightmap.cs
index 83b9c37..2d379bb 100755
--- a/OpenSim/Region/Physics/BulletSPlugin/BSTerrainHeightmap.cs
+++ b/OpenSim/Region/Physics/BulletSPlugin/BSTerrainHeightmap.cs
@@ -136,7 +136,7 @@ public sealed class BSTerrainHeightmap : BSTerrainPhys
     {
         if (m_mapInfo != null)
         {
-            if (m_mapInfo.terrainBody.ptr != IntPtr.Zero)
+            if (m_mapInfo.terrainBody.HasPhysicalBody)
             {
                 BulletSimAPI.RemoveObjectFromWorld2(PhysicsScene.World.ptr, m_mapInfo.terrainBody.ptr);
                 // Frees both the body and the shape.
diff --git a/OpenSim/Region/Physics/BulletSPlugin/BSTerrainManager.cs b/OpenSim/Region/Physics/BulletSPlugin/BSTerrainManager.cs
index 83df360..c28d69d 100755
--- a/OpenSim/Region/Physics/BulletSPlugin/BSTerrainManager.cs
+++ b/OpenSim/Region/Physics/BulletSPlugin/BSTerrainManager.cs
@@ -151,13 +151,13 @@ public sealed class BSTerrainManager
     // Release all the terrain structures we might have allocated
     public void ReleaseGroundPlaneAndTerrain()
     {
-        if (m_groundPlane.ptr != IntPtr.Zero)
+        if (m_groundPlane.HasPhysicalBody)
         {
             if (BulletSimAPI.RemoveObjectFromWorld2(PhysicsScene.World.ptr, m_groundPlane.ptr))
             {
                 BulletSimAPI.DestroyObject2(PhysicsScene.World.ptr, m_groundPlane.ptr);
             }
-            m_groundPlane.ptr = IntPtr.Zero;
+            m_groundPlane.Clear();
         }
 
         ReleaseTerrain();
diff --git a/OpenSim/Region/Physics/BulletSPlugin/BSTerrainMesh.cs b/OpenSim/Region/Physics/BulletSPlugin/BSTerrainMesh.cs
index 6ce767d..3473006 100755
--- a/OpenSim/Region/Physics/BulletSPlugin/BSTerrainMesh.cs
+++ b/OpenSim/Region/Physics/BulletSPlugin/BSTerrainMesh.cs
@@ -94,7 +94,7 @@ public sealed class BSTerrainMesh : BSTerrainPhys
         m_terrainShape = new BulletShape(BulletSimAPI.CreateMeshShape2(PhysicsScene.World.ptr,
                                                     indicesCount, indices, verticesCount, vertices),
                                         BSPhysicsShapeType.SHAPE_MESH);
-        if (m_terrainShape.ptr == IntPtr.Zero)
+        if (!m_terrainShape.HasPhysicalShape)
         {
             // DISASTER!!
             PhysicsScene.DetailLog("{0},BSTerrainMesh.create,failedCreationOfShape", ID);
@@ -107,7 +107,7 @@ public sealed class BSTerrainMesh : BSTerrainPhys
         Quaternion rot = Quaternion.Identity;
 
         m_terrainBody = new BulletBody(id, BulletSimAPI.CreateBodyWithDefaultMotionState2( m_terrainShape.ptr, ID, pos, rot));
-        if (m_terrainBody.ptr == IntPtr.Zero)
+        if (!m_terrainBody.HasPhysicalBody)
         {
             // DISASTER!!
             physicsScene.Logger.ErrorFormat("{0} Failed creation of terrain body! base={1}", LogHeader, TerrainBase);
@@ -140,7 +140,7 @@ public sealed class BSTerrainMesh : BSTerrainPhys
 
     public override void Dispose()
     {
-        if (m_terrainBody.ptr != IntPtr.Zero)
+        if (m_terrainBody.HasPhysicalBody)
         {
             BulletSimAPI.RemoveObjectFromWorld2(PhysicsScene.World.ptr, m_terrainBody.ptr);
             // Frees both the body and the shape.
diff --git a/OpenSim/Region/Physics/BulletSPlugin/BulletSimAPI.cs b/OpenSim/Region/Physics/BulletSPlugin/BulletSimAPI.cs
index 2671995..1559025 100644
--- a/OpenSim/Region/Physics/BulletSPlugin/BulletSimAPI.cs
+++ b/OpenSim/Region/Physics/BulletSPlugin/BulletSimAPI.cs
@@ -53,6 +53,9 @@ public struct BulletSim
 // An allocated Bullet btRigidBody
 public struct BulletBody
 {
+    public BulletBody(uint id) : this(id, IntPtr.Zero)
+    {
+    }
     public BulletBody(uint id, IntPtr xx)
     {
         ID = id;
@@ -64,6 +67,13 @@ public struct BulletBody
     public uint ID;
     public CollisionFilterGroups collisionGroup;
     public CollisionFilterGroups collisionMask;
+
+    public void Clear()
+    {
+        ptr = IntPtr.Zero;
+    }
+    public bool HasPhysicalBody { get { return ptr != IntPtr.Zero; } }
+
     public override string ToString()
     {
         StringBuilder buff = new StringBuilder();
@@ -103,6 +113,13 @@ public struct BulletShape
     public BSPhysicsShapeType type;
     public System.UInt64 shapeKey;
     public bool isNativeShape;
+
+    public void Clear()
+    {
+        ptr = IntPtr.Zero;
+    }
+    public bool HasPhysicalShape { get { return ptr != IntPtr.Zero; } }
+
     public override string ToString()
     {
         StringBuilder buff = new StringBuilder();
@@ -140,6 +157,12 @@ public struct BulletConstraint
         ptr = xx;
     }
     public IntPtr ptr;
+
+    public void Clear()
+    {
+        ptr = IntPtr.Zero;
+    }
+    public bool HasPhysicalConstraint { get { return ptr != IntPtr.Zero; } }
 }
 
 // An allocated HeightMapThing which holds various heightmap info.