Initial update to OpenSim 0.8.2.1 source code.

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);
+    }
+}
+}