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diff --git a/OpenSim/Region/Physics/ConvexDecompositionDotNet/PlaneTri.cs b/OpenSim/Region/Physics/ConvexDecompositionDotNet/PlaneTri.cs
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+++ b/OpenSim/Region/Physics/ConvexDecompositionDotNet/PlaneTri.cs
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+/* The MIT License
+ * 
+ * Copyright (c) 2010 Intel Corporation.
+ * All rights reserved.
+ *
+ * Based on the convexdecomposition library from 
+ * <http://codesuppository.googlecode.com> by John W. Ratcliff and Stan Melax.
+ * 
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ * 
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ * 
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+
+namespace OpenSim.Region.Physics.ConvexDecompositionDotNet
+{
+    public enum PlaneTriResult : int
+    {
+        PTR_FRONT,
+        PTR_BACK,
+        PTR_SPLIT
+    }
+
+    public static class PlaneTri
+    {
+        private static float DistToPt(float3 p, float4 plane)
+        {
+            return p.x * plane.x + p.y * plane.y + p.z * plane.z + plane.w;
+        }
+
+        private static PlaneTriResult getSidePlane(float3 p, float4 plane, float epsilon)
+        {
+            float d = DistToPt(p, plane);
+
+            if ((d + epsilon) > 0f)
+                return PlaneTriResult.PTR_FRONT; // it is 'in front' within the provided epsilon value.
+
+            return PlaneTriResult.PTR_BACK;
+        }
+
+        private static void add(float3 p, float3[] dest, ref int pcount)
+        {
+            dest[pcount++] = new float3(p);
+            Debug.Assert(pcount <= 4);
+        }
+
+        // assumes that the points are on opposite sides of the plane!
+        private static void intersect(float3 p1, float3 p2, float3 split, float4 plane)
+        {
+            float dp1 = DistToPt(p1, plane);
+            float[] dir = new float[3];
+
+            dir[0] = p2[0] - p1[0];
+            dir[1] = p2[1] - p1[1];
+            dir[2] = p2[2] - p1[2];
+
+            float dot1 = dir[0] * plane[0] + dir[1] * plane[1] + dir[2] * plane[2];
+            float dot2 = dp1 - plane[3];
+
+            float t = -(plane[3] + dot2) / dot1;
+
+            split.x = (dir[0] * t) + p1[0];
+            split.y = (dir[1] * t) + p1[1];
+            split.z = (dir[2] * t) + p1[2];
+        }
+
+        public static PlaneTriResult planeTriIntersection(float4 plane, FaceTri triangle, float epsilon, ref float3[] front, out int fcount, ref float3[] back, out int bcount)
+        {
+            fcount = 0;
+            bcount = 0;
+
+            // get the three vertices of the triangle.
+            float3 p1 = triangle.P1;
+            float3 p2 = triangle.P2;
+            float3 p3 = triangle.P3;
+
+            PlaneTriResult r1 = getSidePlane(p1, plane, epsilon); // compute the side of the plane each vertex is on
+            PlaneTriResult r2 = getSidePlane(p2, plane, epsilon);
+            PlaneTriResult r3 = getSidePlane(p3, plane, epsilon);
+
+            if (r1 == r2 && r1 == r3) // if all three vertices are on the same side of the plane.
+            {
+                if (r1 == PlaneTriResult.PTR_FRONT) // if all three are in front of the plane, then copy to the 'front' output triangle.
+                {
+                    add(p1, front, ref fcount);
+                    add(p2, front, ref fcount);
+                    add(p3, front, ref fcount);
+                }
+                else
+                {
+                    add(p1, back, ref bcount); // if all three are in 'back' then copy to the 'back' output triangle.
+                    add(p2, back, ref bcount);
+                    add(p3, back, ref bcount);
+                }
+                return r1; // if all three points are on the same side of the plane return result
+            }
+
+            // ok.. we need to split the triangle at the plane.
+
+            // First test ray segment P1 to P2
+            if (r1 == r2) // if these are both on the same side...
+            {
+                if (r1 == PlaneTriResult.PTR_FRONT)
+                {
+                    add(p1, front, ref fcount);
+                    add(p2, front, ref fcount);
+                }
+                else
+                {
+                    add(p1, back, ref bcount);
+                    add(p2, back, ref bcount);
+                }
+            }
+            else
+            {
+                float3 split = new float3();
+                intersect(p1, p2, split, plane);
+
+                if (r1 == PlaneTriResult.PTR_FRONT)
+                {
+
+                    add(p1, front, ref fcount);
+                    add(split, front, ref fcount);
+
+                    add(split, back, ref bcount);
+                    add(p2, back, ref bcount);
+
+                }
+                else
+                {
+                    add(p1, back, ref bcount);
+                    add(split, back, ref bcount);
+
+                    add(split, front, ref fcount);
+                    add(p2, front, ref fcount);
+                }
+
+            }
+
+            // Next test ray segment P2 to P3
+            if (r2 == r3) // if these are both on the same side...
+            {
+                if (r3 == PlaneTriResult.PTR_FRONT)
+                {
+                    add(p3, front, ref fcount);
+                }
+                else
+                {
+                    add(p3, back, ref bcount);
+                }
+            }
+            else
+            {
+                float3 split = new float3(); // split the point
+                intersect(p2, p3, split, plane);
+
+                if (r3 == PlaneTriResult.PTR_FRONT)
+                {
+                    add(split, front, ref fcount);
+                    add(split, back, ref bcount);
+
+                    add(p3, front, ref fcount);
+                }
+                else
+                {
+                    add(split, front, ref fcount);
+                    add(split, back, ref bcount);
+
+                    add(p3, back, ref bcount);
+                }
+            }
+
+            // Next test ray segment P3 to P1
+            if (r3 != r1) // if these are both on the same side...
+            {
+                float3 split = new float3(); // split the point
+                intersect(p3, p1, split, plane);
+
+                if (r1 == PlaneTriResult.PTR_FRONT)
+                {
+                    add(split, front, ref fcount);
+                    add(split, back, ref bcount);
+                }
+                else
+                {
+                    add(split, front, ref fcount);
+                    add(split, back, ref bcount);
+                }
+            }
+
+            return PlaneTriResult.PTR_SPLIT;
+        }
+    }
+}