diff -Nur opensim-/OpenSim/Region/Physics/Manager/PhysicsScene.cs opensim/OpenSim/Region/Physics/Manager/PhysicsScene.cs
--- opensim-/OpenSim/Region/Physics/Manager/PhysicsScene.cs	2010-10-19 13:27:14.000000000 +0900
+++ opensim/OpenSim/Region/Physics/Manager/PhysicsScene.cs	2010-10-19 13:29:58.000000000 +0900
@@ -172,16 +172,36 @@
             return false;
         }
 
+
+        // by Fumi.Iseki for Mega Region
+        private Vector2 worldExtents = new Vector2((int)Constants.RegionSize, (int)Constants.RegionSize);
+
+        public virtual Vector2 GetWorldExtents()
+        {
+            return worldExtents;
+        }
+
+        public virtual float GetWorldExtentsHeight(float x, float y)
+        {
+            return 0.0f;
+        }
+
+        public virtual void SetWorldExtentsHeight(float x, float y, float heigt)
+        {
+        }
+
         public virtual void Combine(PhysicsScene pScene, Vector3 offset, Vector3 extents)
         {
+            worldExtents = new Vector2(0.0f, 0.0f);
             return;
         }
 
         public virtual void UnCombine(PhysicsScene pScene)
         {
-            
+            worldExtents = new Vector2((int)Constants.RegionSize, (int)Constants.RegionSize);
         }
 
+
         /// <summary>
         /// Queue a raycast against the physics scene.
         /// The provided callback method will be called when the raycast is complete
diff -Nur opensim-/OpenSim/Region/Physics/OdePlugin/OdePlugin.cs opensim/OpenSim/Region/Physics/OdePlugin/OdePlugin.cs
--- opensim-/OpenSim/Region/Physics/OdePlugin/OdePlugin.cs	2010-10-19 13:27:14.000000000 +0900
+++ opensim/OpenSim/Region/Physics/OdePlugin/OdePlugin.cs	2010-10-19 13:29:58.000000000 +0900
@@ -322,6 +322,13 @@
 
         private ODERayCastRequestManager m_rayCastManager;
 
+
+        // Fumi.Iseki for Mega Region
+        private int combineXsize = 1;
+        private int combineYsize = 1;
+        private Vector2 worldExtents = new Vector2((int)Constants.RegionSize, (int)Constants.RegionSize);
+
+
         /// <summary>
         /// Initiailizes the scene
         /// Sets many properties that ODE requires to be stable
@@ -1588,14 +1595,66 @@
 
         #endregion
 
+
+        // Fumi.Iseki for MegaRegion
+        public override Vector2 GetWorldExtents()
+        {
+            return WorldExtents;
+        }
+        
+
+        public override float GetWorldExtentsHeight(float x, float y)
+        {
+            return GetTerrainHeightAtXY(x, y);
+        }
+
+
+        public override void SetWorldExtentsHeight(float x, float y, float height)
+        {
+            int offsetX = ((int)(x / (int)Constants.RegionSize)) * (int)Constants.RegionSize;
+            int offsetY = ((int)(y / (int)Constants.RegionSize)) * (int)Constants.RegionSize;
+
+            IntPtr heightFieldGeom = IntPtr.Zero;
+
+            if (RegionTerrain.TryGetValue(new Vector3(offsetX,offsetY,0), out heightFieldGeom))
+            {
+                if (heightFieldGeom != IntPtr.Zero)
+                {
+                    if (TerrainHeightFieldHeights.ContainsKey(heightFieldGeom))
+                    {
+                        int index;
+
+                        if ((int)x > WorldExtents.X || (int)y > WorldExtents.Y || (int)x < 0 || (int)y < 0) return;
+
+                        x = x - offsetX;
+                        y = y - offsetY;
+                        index = (int)((int)x * ((int)Constants.RegionSize + 2) + (int)y);
+
+                        if (index < TerrainHeightFieldHeights[heightFieldGeom].Length)
+                        {
+                            TerrainHeightFieldHeights[heightFieldGeom][index] = height;
+                        }
+                    }
+                }
+            }
+
+            return;
+        } 
+
+
         public override void Combine(PhysicsScene pScene, Vector3 offset, Vector3 extents)
         {
             m_worldOffset = offset;
-            WorldExtents = new Vector2(extents.X, extents.Y);
             m_parentScene = pScene;
-            
+
+            if (worldExtents.X!=extents.X && worldExtents.Y==extents.Y) combineXsize++;
+            if (worldExtents.X==extents.X && worldExtents.Y!=extents.Y) combineYsize++;
+
+            worldExtents = new Vector2(extents.X, extents.Y);
+            WorldExtents = new Vector2(Constants.RegionSize*combineXsize, Constants.RegionSize*combineYsize);
         }
         
+
         // Recovered for use by fly height. Kitto Flora
         public float GetTerrainHeightAtXY(float x, float y)
         {
diff -Nur opensim-/OpenSim/Region/ScriptEngine/Shared/Api/Implementation/LSL_Api.cs opensim/OpenSim/Region/ScriptEngine/Shared/Api/Implementation/LSL_Api.cs
--- opensim-/OpenSim/Region/ScriptEngine/Shared/Api/Implementation/LSL_Api.cs	2010-10-19 13:27:14.000000000 +0900
+++ opensim/OpenSim/Region/ScriptEngine/Shared/Api/Implementation/LSL_Api.cs	2010-10-19 13:29:58.000000000 +0900
@@ -1111,19 +1111,34 @@
 
             //Get the slope normal.  This gives us the equation of the plane tangent to the slope.
             LSL_Vector vsn = llGroundNormal(offset);
+            float baseheight = 0.0f;
 
-            // Clamp to valid position
-            if (pos.X < 0)
-                pos.X = 0;
-            else if (pos.X >= World.Heightmap.Width)
-                pos.X = World.Heightmap.Width - 1;
-            if (pos.Y < 0)
-                pos.Y = 0;
-            else if (pos.Y >= World.Heightmap.Height)
-                pos.Y = World.Heightmap.Height - 1;
+            // for Mega Region by Fumi.Iseki
+            Vector2 worldExtents = World.PhysicsScene.GetWorldExtents();
+            if (worldExtents.X>World.Heightmap.Width && worldExtents.Y>World.Heightmap.Height)
+            {
+                if (pos.X < 0) pos.X = 0;
+                else if (pos.X >= worldExtents.X) pos.X = worldExtents.X - 1;
+                if (pos.Y < 0) pos.Y = 0;
+                else if (pos.Y >= worldExtents.Y) pos.Y = worldExtents.Y - 1;
+
+                baseheight = World.PhysicsScene.GetWorldExtentsHeight(pos.X, pos.Y);
+            }
+            else
+            {
+                // Clamp to valid position
+                if (pos.X < 0)
+                   pos.X = 0;
+                else if (pos.X >= World.Heightmap.Width)
+                   pos.X = World.Heightmap.Width - 1;
+                if (pos.Y < 0)
+                   pos.Y = 0;
+                else if (pos.Y >= World.Heightmap.Height)
+                   pos.Y = World.Heightmap.Height - 1;
 
-            //Get the height for the integer coordinates from the Heightmap
-            float baseheight = (float)World.Heightmap[(int)pos.X, (int)pos.Y];
+                //Get the height for the integer coordinates from the Heightmap
+                baseheight = (float)World.Heightmap[(int)pos.X, (int)pos.Y];
+            }
 
             //Calculate the difference between the actual coordinates and the integer coordinates
             float xdiff = pos.X - (float)((int)pos.X);
@@ -5742,33 +5757,64 @@
             Vector3 pos = m_host.GetWorldPosition() + new Vector3((float)offset.x,
                                                                 (float)offset.y,
                                                                 (float)offset.z);
-            // Clamp to valid position
-            if (pos.X < 0)
-                pos.X = 0;
-            else if (pos.X >= World.Heightmap.Width)
-                pos.X = World.Heightmap.Width - 1;
-            if (pos.Y < 0)
-                pos.Y = 0;
-            else if (pos.Y >= World.Heightmap.Height)
-                pos.Y = World.Heightmap.Height - 1;
-
-            //Find two points in addition to the position to define a plane
-            Vector3 p0 = new Vector3(pos.X, pos.Y,
-                                     (float)World.Heightmap[(int)pos.X, (int)pos.Y]);
-            Vector3 p1 = new Vector3();
-            Vector3 p2 = new Vector3();
-            if ((pos.X + 1.0f) >= World.Heightmap.Width)
-                p1 = new Vector3(pos.X + 1.0f, pos.Y,
-                            (float)World.Heightmap[(int)pos.X, (int)pos.Y]);
-            else
-                p1 = new Vector3(pos.X + 1.0f, pos.Y,
-                            (float)World.Heightmap[(int)(pos.X + 1.0f), (int)pos.Y]);
-            if ((pos.Y + 1.0f) >= World.Heightmap.Height)
-                p2 = new Vector3(pos.X, pos.Y + 1.0f,
-                            (float)World.Heightmap[(int)pos.X, (int)pos.Y]);
+
+            Vector3 p0, p1, p2;
+
+            // for Mega Region by Fumi.Iseki
+            Vector2 worldExtents = World.PhysicsScene.GetWorldExtents();
+            if (worldExtents.X>World.Heightmap.Width && worldExtents.Y>World.Heightmap.Height)
+            {
+                if (pos.X < 0) pos.X = 0;
+                else if (pos.X >= worldExtents.X) pos.X = worldExtents.X - 1;
+                if (pos.Y < 0) pos.Y = 0;
+                else if (pos.Y >= worldExtents.Y) pos.Y = worldExtents.Y - 1;
+
+                float height = World.PhysicsScene.GetWorldExtentsHeight(pos.X, pos.Y);
+
+                p0 = new Vector3(pos.X, pos.Y, height);
+                p1 = new Vector3();
+                p2 = new Vector3();
+
+                if ((pos.X + 1.0f) >= worldExtents.X)
+                    p1 = new Vector3(pos.X+1.0f, pos.Y, height);
+                else
+                    p1 = new Vector3(pos.X+1.0f, pos.Y, World.PhysicsScene.GetWorldExtentsHeight(pos.X+1.0f, pos.Y));
+
+                if ((pos.Y + 1.0f) >= worldExtents.Y)
+                    p2 = new Vector3(pos.X, pos.Y+1.0f, height);
+                else
+                    p2 = new Vector3(pos.X, pos.Y+1.0f, World.PhysicsScene.GetWorldExtentsHeight(pos.X, pos.Y+1.0f));
+            }
             else
-                p2 = new Vector3(pos.X, pos.Y + 1.0f,
-                            (float)World.Heightmap[(int)pos.X, (int)(pos.Y + 1.0f)]);
+            {
+                // Clamp to valid position
+                if (pos.X < 0)
+                    pos.X = 0;
+                else if (pos.X >= World.Heightmap.Width)
+                    pos.X = World.Heightmap.Width - 1;
+                if (pos.Y < 0)
+                    pos.Y = 0;
+                else if (pos.Y >= World.Heightmap.Height)
+                    pos.Y = World.Heightmap.Height - 1;
+
+                //Find two points in addition to the position to define a plane
+                p0 = new Vector3(pos.X, pos.Y,
+                                         (float)World.Heightmap[(int)pos.X, (int)pos.Y]);
+                p1 = new Vector3();
+                p2 = new Vector3();
+                if ((pos.X + 1.0f) >= World.Heightmap.Width)
+                    p1 = new Vector3(pos.X + 1.0f, pos.Y,
+                                (float)World.Heightmap[(int)pos.X, (int)pos.Y]);
+                else
+                    p1 = new Vector3(pos.X + 1.0f, pos.Y,
+                                (float)World.Heightmap[(int)(pos.X + 1.0f), (int)pos.Y]);
+                if ((pos.Y + 1.0f) >= World.Heightmap.Height)
+                    p2 = new Vector3(pos.X, pos.Y + 1.0f,
+                                (float)World.Heightmap[(int)pos.X, (int)pos.Y]);
+                else
+                    p2 = new Vector3(pos.X, pos.Y + 1.0f,
+                                (float)World.Heightmap[(int)pos.X, (int)(pos.Y + 1.0f)]);
+            }
 
             //Find normalized vectors from p0 to p1 and p0 to p2
             Vector3 v0 = new Vector3(p1.X - p0.X, p1.Y - p0.Y, p1.Z - p0.Z);