Merge of ubitworkvarnew with opensim/master as of 20150905.

This integrates the OpenSim refactoring to make physics, etc into modules.
AVN physics hasn't been moved to new location.
Does not compile yet.

Merge branch 'osmaster' into mbworknew1

1 files changed, 584 insertions, 0 deletions

diff --git a/OpenSim/Region/PhysicsModules/BulletS/BSTerrainManager.cs b/OpenSim/Region/PhysicsModules/BulletS/BSTerrainManager.cs
new file mode 100755
index 0000000..d11baa6
--- /dev/null
+++ b/OpenSim/Region/PhysicsModules/BulletS/BSTerrainManager.cs
@@ -0,0 +1,584 @@
+/*
+ * 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 OpenSim.Framework;
+using OpenSim.Region.Framework;
+using OpenSim.Region.PhysicsModules.SharedBase;
+
+using Nini.Config;
+using log4net;
+
+using OpenMetaverse;
+
+namespace OpenSim.Region.PhysicsModule.BulletS
+{
+
+// The physical implementation of the terrain is wrapped in this class.
+public abstract class BSTerrainPhys : IDisposable
+{
+    public enum TerrainImplementation
+    {
+        Heightmap   = 0,
+        Mesh        = 1
+    }
+
+    protected BSScene m_physicsScene { get; private set; }
+    // Base of the region in world coordinates. Coordinates inside the region are relative to this.
+    public Vector3 TerrainBase { get; private set; }
+    public uint ID { get; private set; }
+
+    public BSTerrainPhys(BSScene physicsScene, Vector3 regionBase, uint id)
+    {
+        m_physicsScene = physicsScene;
+        TerrainBase = regionBase;
+        ID = id;
+    }
+    public abstract void Dispose();
+    public abstract float GetTerrainHeightAtXYZ(Vector3 pos);
+    public abstract float GetWaterLevelAtXYZ(Vector3 pos);
+}
+
+// ==========================================================================================
+public sealed class BSTerrainManager : IDisposable
+{
+    static string LogHeader = "[BULLETSIM TERRAIN MANAGER]";
+
+    // These height values are fractional so the odd values will be
+    //     noticable when debugging.
+    public const float HEIGHT_INITIALIZATION = 24.987f;
+    public const float HEIGHT_INITIAL_LASTHEIGHT = 24.876f;
+    public const float HEIGHT_GETHEIGHT_RET = 24.765f;
+    public const float WATER_HEIGHT_GETHEIGHT_RET = 19.998f;
+
+    // If the min and max height are equal, we reduce the min by this
+    //    amount to make sure that a bounding box is built for the terrain.
+    public const float HEIGHT_EQUAL_FUDGE = 0.2f;
+
+    // Until the whole simulator is changed to pass us the region size, we rely on constants.
+    public Vector3 DefaultRegionSize = new Vector3(Constants.RegionSize, Constants.RegionSize, Constants.RegionHeight);
+
+    // The scene that I am part of
+    private BSScene m_physicsScene { get; set; }
+
+    // The ground plane created to keep thing from falling to infinity.
+    private BulletBody m_groundPlane;
+
+    // If doing mega-regions, if we're region zero we will be managing multiple
+    //    region terrains since region zero does the physics for the whole mega-region.
+    private Dictionary<Vector3, BSTerrainPhys> m_terrains;
+
+    // Flags used to know when to recalculate the height.
+    private bool m_terrainModified = false;
+
+    // If we are doing mega-regions, terrains are added from TERRAIN_ID to m_terrainCount.
+    // This is incremented before assigning to new region so it is the last ID allocated.
+    private uint m_terrainCount = BSScene.CHILDTERRAIN_ID - 1;
+    public uint HighestTerrainID { get {return m_terrainCount; } }
+
+    // If doing mega-regions, this holds our offset from region zero of
+    //     the mega-regions. "parentScene" points to the PhysicsScene of region zero.
+    private Vector3 m_worldOffset;
+    // If the parent region (region 0), this is the extent of the combined regions
+    //     relative to the origin of region zero
+    private Vector3 m_worldMax;
+    private PhysicsScene MegaRegionParentPhysicsScene { get; set; }
+
+    public BSTerrainManager(BSScene physicsScene, Vector3 regionSize)
+    {
+        m_physicsScene = physicsScene;
+        DefaultRegionSize = regionSize;
+
+        m_terrains = new Dictionary<Vector3,BSTerrainPhys>();
+
+        // Assume one region of default size
+        m_worldOffset = Vector3.Zero;
+        m_worldMax = new Vector3(DefaultRegionSize);
+        MegaRegionParentPhysicsScene = null;
+    }
+
+    public void Dispose()
+    {
+        ReleaseGroundPlaneAndTerrain();
+    }
+
+    // Create the initial instance of terrain and the underlying ground plane.
+    // This is called from the initialization routine so we presume it is
+    //    safe to call Bullet in real time. We hope no one is moving prims around yet.
+    public void CreateInitialGroundPlaneAndTerrain()
+    {
+        DetailLog("{0},BSTerrainManager.CreateInitialGroundPlaneAndTerrain,region={1}", BSScene.DetailLogZero, m_physicsScene.RegionName);
+        // The ground plane is here to catch things that are trying to drop to negative infinity
+        BulletShape groundPlaneShape = m_physicsScene.PE.CreateGroundPlaneShape(BSScene.GROUNDPLANE_ID, 1f, BSParam.TerrainCollisionMargin);
+        Vector3 groundPlaneAltitude = new Vector3(0f, 0f, BSParam.TerrainGroundPlane);
+        m_groundPlane = m_physicsScene.PE.CreateBodyWithDefaultMotionState(groundPlaneShape,
+                                        BSScene.GROUNDPLANE_ID, groundPlaneAltitude, Quaternion.Identity);
+
+        // Everything collides with the ground plane.
+        m_groundPlane.collisionType = CollisionType.Groundplane;
+
+        m_physicsScene.PE.AddObjectToWorld(m_physicsScene.World, m_groundPlane);
+        m_physicsScene.PE.UpdateSingleAabb(m_physicsScene.World, m_groundPlane);
+
+        // Ground plane does not move
+        m_physicsScene.PE.ForceActivationState(m_groundPlane, ActivationState.DISABLE_SIMULATION);
+
+        BSTerrainPhys initialTerrain = new BSTerrainHeightmap(m_physicsScene, Vector3.Zero, BSScene.TERRAIN_ID, DefaultRegionSize);
+        lock (m_terrains)
+        {
+            // Build an initial terrain and put it in the world. This quickly gets replaced by the real region terrain.
+            m_terrains.Add(Vector3.Zero, initialTerrain);
+        }
+    }
+
+    // Release all the terrain structures we might have allocated
+    public void ReleaseGroundPlaneAndTerrain()
+    {
+        DetailLog("{0},BSTerrainManager.ReleaseGroundPlaneAndTerrain,region={1}", BSScene.DetailLogZero, m_physicsScene.RegionName);
+        if (m_groundPlane.HasPhysicalBody)
+        {
+            if (m_physicsScene.PE.RemoveObjectFromWorld(m_physicsScene.World, m_groundPlane))
+            {
+                m_physicsScene.PE.DestroyObject(m_physicsScene.World, m_groundPlane);
+            }
+            m_groundPlane.Clear();
+        }
+
+        ReleaseTerrain();
+    }
+
+    // Release all the terrain we have allocated
+    public void ReleaseTerrain()
+    {
+        lock (m_terrains)
+        {
+            foreach (KeyValuePair<Vector3, BSTerrainPhys> kvp in m_terrains)
+            {
+                kvp.Value.Dispose();
+            }
+            m_terrains.Clear();
+        }
+    }
+
+    // The simulator wants to set a new heightmap for the terrain.
+    public void SetTerrain(float[] heightMap) {
+        float[] localHeightMap = heightMap;
+        // If there are multiple requests for changes to the same terrain between ticks,
+        //      only do that last one.
+        m_physicsScene.PostTaintObject("TerrainManager.SetTerrain-"+ m_worldOffset.ToString(), 0, delegate()
+        {
+            if (m_worldOffset != Vector3.Zero && MegaRegionParentPhysicsScene != null)
+            {
+                // If a child of a mega-region, we shouldn't have any terrain allocated for us
+                ReleaseGroundPlaneAndTerrain();
+                // If doing the mega-prim stuff and we are the child of the zero region,
+                //    the terrain is added to our parent
+                if (MegaRegionParentPhysicsScene is BSScene)
+                {
+                    DetailLog("{0},SetTerrain.ToParent,offset={1},worldMax={2}", BSScene.DetailLogZero, m_worldOffset, m_worldMax);
+                    ((BSScene)MegaRegionParentPhysicsScene).TerrainManager.AddMegaRegionChildTerrain(
+                                        BSScene.CHILDTERRAIN_ID, localHeightMap, m_worldOffset, m_worldOffset + DefaultRegionSize);
+                }
+            }
+            else
+            {
+                // If not doing the mega-prim thing, just change the terrain
+                DetailLog("{0},SetTerrain.Existing", BSScene.DetailLogZero);
+
+                UpdateTerrain(BSScene.TERRAIN_ID, localHeightMap, m_worldOffset, m_worldOffset + DefaultRegionSize);
+            }
+        });
+    }
+
+    // Another region is calling this region and passing a terrain.
+    // A region that is not the mega-region root will pass its terrain to the root region so the root region
+    //      physics engine will have all the terrains.
+    private void AddMegaRegionChildTerrain(uint id, float[] heightMap, Vector3 minCoords, Vector3 maxCoords)
+    {
+        // Since we are called by another region's thread, the action must be rescheduled onto our processing thread.
+        m_physicsScene.PostTaintObject("TerrainManager.AddMegaRegionChild" + minCoords.ToString(), id, delegate()
+        {
+            UpdateTerrain(id, heightMap, minCoords, maxCoords);
+        });
+    }
+
+    // If called for terrain has has not been previously allocated, a new terrain will be built
+    //     based on the passed information. The 'id' should be either the terrain id or
+    //     BSScene.CHILDTERRAIN_ID. If the latter, a new child terrain ID will be allocated and used.
+    //     The latter feature is for creating child terrains for mega-regions.
+    // If there is an existing terrain body, a new
+    //     terrain shape is created and added to the body.
+    //     This call is most often used to update the heightMap and parameters of the terrain.
+    // (The above does suggest that some simplification/refactoring is in order.)
+    // Called during taint-time.
+    private void UpdateTerrain(uint id, float[] heightMap, Vector3 minCoords, Vector3 maxCoords)
+    {
+        // Find high and low points of passed heightmap.
+        // The min and max passed in is usually the area objects can be in (maximum
+        //     object height, for instance). The terrain wants the bounding box for the
+        //     terrain so replace passed min and max Z with the actual terrain min/max Z.
+        float minZ = float.MaxValue;
+        float maxZ = float.MinValue;
+        foreach (float height in heightMap)
+        {
+            if (height < minZ) minZ = height;
+            if (height > maxZ) maxZ = height;
+        }
+        if (minZ == maxZ)
+        {
+            // If min and max are the same, reduce min a little bit so a good bounding box is created.
+            minZ -= BSTerrainManager.HEIGHT_EQUAL_FUDGE;
+        }
+        minCoords.Z = minZ;
+        maxCoords.Z = maxZ;
+
+        DetailLog("{0},BSTerrainManager.UpdateTerrain,call,id={1},minC={2},maxC={3}",
+                            BSScene.DetailLogZero, id, minCoords, maxCoords);
+
+        Vector3 terrainRegionBase = new Vector3(minCoords.X, minCoords.Y, 0f);
+
+        lock (m_terrains)
+        {
+            BSTerrainPhys terrainPhys;
+            if (m_terrains.TryGetValue(terrainRegionBase, out terrainPhys))
+            {
+                // There is already a terrain in this spot. Free the old and build the new.
+                DetailLog("{0},BSTerrainManager.UpdateTerrain:UpdateExisting,call,id={1},base={2},minC={3},maxC={4}",
+                                BSScene.DetailLogZero, id, terrainRegionBase, minCoords, maxCoords);
+
+                // Remove old terrain from the collection
+                m_terrains.Remove(terrainRegionBase);
+                // Release any physical memory it may be using.
+                terrainPhys.Dispose();
+
+                if (MegaRegionParentPhysicsScene == null)
+                {
+                    // This terrain is not part of the mega-region scheme. Create vanilla terrain.
+                    BSTerrainPhys newTerrainPhys = BuildPhysicalTerrain(terrainRegionBase, id, heightMap, minCoords, maxCoords);
+                    m_terrains.Add(terrainRegionBase, newTerrainPhys);
+
+                    m_terrainModified = true;
+                }
+                else
+                {
+                    // It's possible that Combine() was called after this code was queued.
+                    // If we are a child of combined regions, we don't create any terrain for us.
+                    DetailLog("{0},BSTerrainManager.UpdateTerrain:AmACombineChild,taint", BSScene.DetailLogZero);
+
+                    // Get rid of any terrain that may have been allocated for us.
+                    ReleaseGroundPlaneAndTerrain();
+
+                    // I hate doing this, but just bail
+                    return;
+                }
+            }
+            else
+            {
+                // We don't know about this terrain so either we are creating a new terrain or
+                //    our mega-prim child is giving us a new terrain to add to the phys world
+
+                // if this is a child terrain, calculate a unique terrain id
+                uint newTerrainID = id;
+                if (newTerrainID >= BSScene.CHILDTERRAIN_ID)
+                    newTerrainID = ++m_terrainCount;
+
+                DetailLog("{0},BSTerrainManager.UpdateTerrain:NewTerrain,taint,newID={1},minCoord={2},maxCoord={3}",
+                                            BSScene.DetailLogZero, newTerrainID, minCoords, maxCoords);
+                BSTerrainPhys newTerrainPhys = BuildPhysicalTerrain(terrainRegionBase, id, heightMap, minCoords, maxCoords);
+                m_terrains.Add(terrainRegionBase, newTerrainPhys);
+
+                m_terrainModified = true;
+            }
+        }
+    }
+
+    // TODO: redo terrain implementation selection to allow other base types than heightMap.
+    private BSTerrainPhys BuildPhysicalTerrain(Vector3 terrainRegionBase, uint id, float[] heightMap, Vector3 minCoords, Vector3 maxCoords)
+    {
+        m_physicsScene.Logger.DebugFormat("{0} Terrain for {1}/{2} created with {3}",
+                                            LogHeader, m_physicsScene.RegionName, terrainRegionBase,
+                                            (BSTerrainPhys.TerrainImplementation)BSParam.TerrainImplementation);
+        BSTerrainPhys newTerrainPhys = null;
+        switch ((int)BSParam.TerrainImplementation)
+        {
+            case (int)BSTerrainPhys.TerrainImplementation.Heightmap:
+                newTerrainPhys = new BSTerrainHeightmap(m_physicsScene, terrainRegionBase, id,
+                                            heightMap, minCoords, maxCoords);
+                break;
+            case (int)BSTerrainPhys.TerrainImplementation.Mesh:
+                newTerrainPhys = new BSTerrainMesh(m_physicsScene, terrainRegionBase, id,
+                                            heightMap, minCoords, maxCoords);
+                break;
+            default:
+                m_physicsScene.Logger.ErrorFormat("{0} Bad terrain implementation specified. Type={1}/{2},Region={3}/{4}",
+                                            LogHeader,
+                                            (int)BSParam.TerrainImplementation,
+                                            BSParam.TerrainImplementation,
+                                            m_physicsScene.RegionName, terrainRegionBase);
+                break;
+        }
+        return newTerrainPhys;
+    }
+
+    // Return 'true' of this position is somewhere in known physical terrain space
+    public bool IsWithinKnownTerrain(Vector3 pos)
+    {
+        Vector3 terrainBaseXYZ;
+        BSTerrainPhys physTerrain;
+        return GetTerrainPhysicalAtXYZ(pos, out physTerrain, out terrainBaseXYZ);
+    }
+
+    // Return a new position that is over known terrain if the position is outside our terrain.
+    public Vector3 ClampPositionIntoKnownTerrain(Vector3 pPos)
+    {
+        float edgeEpsilon = 0.1f;
+
+        Vector3 ret = pPos;
+
+        // First, base addresses are never negative so correct for that possible problem.
+        if (ret.X < 0f || ret.Y < 0f)
+        {
+            ret.X = Util.Clamp<float>(ret.X, 0f, 1000000f);
+            ret.Y = Util.Clamp<float>(ret.Y, 0f, 1000000f);
+            DetailLog("{0},BSTerrainManager.ClampPositionToKnownTerrain,zeroingNegXorY,oldPos={1},newPos={2}",
+                                        BSScene.DetailLogZero, pPos, ret);
+        }
+
+        // Can't do this function if we don't know about any terrain.
+        if (m_terrains.Count == 0)
+            return ret;
+
+        int loopPrevention = 10;
+        Vector3 terrainBaseXYZ;
+        BSTerrainPhys physTerrain;
+        while (!GetTerrainPhysicalAtXYZ(ret, out physTerrain, out terrainBaseXYZ))
+        {
+            // The passed position is not within a known terrain area.
+            // NOTE that GetTerrainPhysicalAtXYZ will set 'terrainBaseXYZ' to the base of the unfound region.
+
+            // Must be off the top of a region. Find an adjacent region to move into.
+            //     The returned terrain is always 'lower'. That is, closer to <0,0>.
+            Vector3 adjacentTerrainBase = FindAdjacentTerrainBase(terrainBaseXYZ);
+
+            if (adjacentTerrainBase.X < terrainBaseXYZ.X)
+            {
+                // moving down into a new region in the X dimension. New position will be the max in the new base.
+                ret.X = adjacentTerrainBase.X + DefaultRegionSize.X - edgeEpsilon;
+            }
+            if (adjacentTerrainBase.Y < terrainBaseXYZ.Y)
+            {
+                // moving down into a new region in the X dimension. New position will be the max in the new base.
+                ret.Y = adjacentTerrainBase.Y + DefaultRegionSize.Y - edgeEpsilon;
+            }
+            DetailLog("{0},BSTerrainManager.ClampPositionToKnownTerrain,findingAdjacentRegion,adjacentRegBase={1},oldPos={2},newPos={3}",
+                                        BSScene.DetailLogZero, adjacentTerrainBase, pPos, ret);
+
+            if (loopPrevention-- < 0f)
+            {
+                // The 'while' is a little dangerous so this prevents looping forever if the
+                //    mapping of the terrains ever gets messed up (like nothing at <0,0>) or
+                //    the list of terrains is in transition.
+                DetailLog("{0},BSTerrainManager.ClampPositionToKnownTerrain,suppressingFindAdjacentRegionLoop", BSScene.DetailLogZero);
+                break;
+            }
+        }
+
+        return ret;
+    }
+
+    // Given an X and Y, find the height of the terrain.
+    // Since we could be handling multiple terrains for a mega-region,
+    //    the base of the region is calcuated assuming all regions are
+    //    the same size and that is the default.
+    // Once the heightMapInfo is found, we have all the information to
+    //    compute the offset into the array.
+    private float lastHeightTX = 999999f;
+    private float lastHeightTY = 999999f;
+    private float lastHeight = HEIGHT_INITIAL_LASTHEIGHT;
+    public float GetTerrainHeightAtXYZ(Vector3 pos)
+    {
+        float tX = pos.X;
+        float tY = pos.Y;
+        // You'd be surprized at the number of times this routine is called
+        //    with the same parameters as last time.
+        if (!m_terrainModified && (lastHeightTX == tX) && (lastHeightTY == tY))
+            return lastHeight;
+        m_terrainModified = false;
+
+        lastHeightTX = tX;
+        lastHeightTY = tY;
+        float ret = HEIGHT_GETHEIGHT_RET;
+
+        Vector3 terrainBaseXYZ;
+        BSTerrainPhys physTerrain;
+        if (GetTerrainPhysicalAtXYZ(pos, out physTerrain, out terrainBaseXYZ))
+        {
+            ret = physTerrain.GetTerrainHeightAtXYZ(pos - terrainBaseXYZ);
+        }
+        else
+        {
+            m_physicsScene.Logger.ErrorFormat("{0} GetTerrainHeightAtXY: terrain not found: region={1}, x={2}, y={3}",
+                    LogHeader, m_physicsScene.RegionName, tX, tY);
+            DetailLog("{0},BSTerrainManager.GetTerrainHeightAtXYZ,terrainNotFound,pos={1},base={2}",
+                                BSScene.DetailLogZero, pos, terrainBaseXYZ);
+        }
+
+        lastHeight = ret;
+        return ret;
+    }
+
+    public float GetWaterLevelAtXYZ(Vector3 pos)
+    {
+        float ret = WATER_HEIGHT_GETHEIGHT_RET;
+
+        Vector3 terrainBaseXYZ;
+        BSTerrainPhys physTerrain;
+        if (GetTerrainPhysicalAtXYZ(pos, out physTerrain, out terrainBaseXYZ))
+        {
+            ret = physTerrain.GetWaterLevelAtXYZ(pos);
+        }
+        else
+        {
+            m_physicsScene.Logger.ErrorFormat("{0} GetWaterHeightAtXY: terrain not found: pos={1}, terrainBase={2}, height={3}",
+                    LogHeader, m_physicsScene.RegionName, pos, terrainBaseXYZ, ret);
+        }
+        return ret;
+    }
+
+    // Given an address, return 'true' of there is a description of that terrain and output
+    //    the descriptor class and the 'base' fo the addresses therein.
+    private bool GetTerrainPhysicalAtXYZ(Vector3 pos, out BSTerrainPhys outPhysTerrain, out Vector3 outTerrainBase)
+    {
+        bool ret = false;
+
+        Vector3 terrainBaseXYZ = Vector3.Zero;
+        if (pos.X < 0f || pos.Y < 0f)
+        {
+            // We don't handle negative addresses so just make up a base that will not be found.
+            terrainBaseXYZ = new Vector3(-DefaultRegionSize.X, -DefaultRegionSize.Y, 0f);
+        }
+        else
+        {
+            int offsetX = ((int)(pos.X / (int)DefaultRegionSize.X)) * (int)DefaultRegionSize.X;
+            int offsetY = ((int)(pos.Y / (int)DefaultRegionSize.Y)) * (int)DefaultRegionSize.Y;
+            terrainBaseXYZ = new Vector3(offsetX, offsetY, 0f);
+        }
+
+        BSTerrainPhys physTerrain = null;
+        lock (m_terrains)
+        {
+            ret = m_terrains.TryGetValue(terrainBaseXYZ, out physTerrain);
+        }
+        outTerrainBase = terrainBaseXYZ;
+        outPhysTerrain = physTerrain;
+        return ret;
+    }
+
+    // Given a terrain base, return a terrain base for a terrain that is closer to <0,0> than
+    //   this one. Usually used to return an out of bounds object to a known place.
+    private Vector3 FindAdjacentTerrainBase(Vector3 pTerrainBase)
+    {
+        Vector3 ret = pTerrainBase;
+
+        // Can't do this function if we don't know about any terrain.
+        if (m_terrains.Count == 0)
+            return ret;
+
+        // Just some sanity
+        ret.X = Util.Clamp<float>(ret.X, 0f, 1000000f);
+        ret.Y = Util.Clamp<float>(ret.Y, 0f, 1000000f);
+        ret.Z = 0f;
+
+        lock (m_terrains)
+        {
+            // Once down to the <0,0> region, we have to be done.
+            while (ret.X > 0f || ret.Y > 0f)
+            {
+                if (ret.X > 0f)
+                {
+                    ret.X = Math.Max(0f, ret.X - DefaultRegionSize.X);
+                    DetailLog("{0},BSTerrainManager.FindAdjacentTerrainBase,reducingX,terrainBase={1}", BSScene.DetailLogZero, ret);
+                    if (m_terrains.ContainsKey(ret))
+                        break;
+                }
+                if (ret.Y > 0f)
+                {
+                    ret.Y = Math.Max(0f, ret.Y - DefaultRegionSize.Y);
+                    DetailLog("{0},BSTerrainManager.FindAdjacentTerrainBase,reducingY,terrainBase={1}", BSScene.DetailLogZero, ret);
+                    if (m_terrains.ContainsKey(ret))
+                        break;
+                }
+            }
+        }
+
+        return ret;
+    }
+
+    // Although no one seems to check this, I do support combining.
+    public bool SupportsCombining()
+    {
+        return true;
+    }
+
+    // This routine is called two ways:
+    //    One with 'offset' and 'pScene' zero and null but 'extents' giving the maximum
+    //        extent of the combined regions. This is to inform the parent of the size
+    //        of the combined regions.
+    //    and one with 'offset' as the offset of the child region to the base region,
+    //        'pScene' pointing to the parent and 'extents' of zero. This informs the
+    //        child of its relative base and new parent.
+    public void Combine(PhysicsScene pScene, Vector3 offset, Vector3 extents)
+    {
+        m_worldOffset = offset;
+        m_worldMax = extents;
+        MegaRegionParentPhysicsScene = pScene;
+        if (pScene != null)
+        {
+            // We are a child.
+            // We want m_worldMax to be the highest coordinate of our piece of terrain.
+            m_worldMax = offset + DefaultRegionSize;
+        }
+        DetailLog("{0},BSTerrainManager.Combine,offset={1},extents={2},wOffset={3},wMax={4}",
+                        BSScene.DetailLogZero, offset, extents, m_worldOffset, m_worldMax);
+    }
+
+    // Unhook all the combining that I know about.
+    public void UnCombine(PhysicsScene pScene)
+    {
+        // Just like ODE, we don't do anything yet.
+        DetailLog("{0},BSTerrainManager.UnCombine", BSScene.DetailLogZero);
+    }
+
+
+    private void DetailLog(string msg, params Object[] args)
+    {
+        m_physicsScene.PhysicsLogging.Write(msg, args);
+    }
+}
+}