When calling osNpcMoveTo(), rotate the avatar in the direction of travel.

This stops the npc walking backwards if the target is directly behind.
This means that the npc no longer returns to its original rotation once movement has finished.
If you want this behaviour, please store and reset the original rotation after movement.
This is somewhat to address http://opensimulator.org/mantis/view.php?id=5678

OpenSim/Region/Framework/Scenes/ScenePresence.cs

@@ -585,7 +585,11 @@ namespace OpenSim.Region.Framework.Scenes
         public Quaternion Rotation
         {
             get { return m_bodyRot; }
-            set { m_bodyRot = value; }
+            set
+            {
+                m_bodyRot = value;
+                m_log.DebugFormat("[SCENE PRESENCE]: Body rot for {0} set to {1}", Name, m_bodyRot);
+            }
         }
 
         public Quaternion PreviousRotation
@@ -1711,7 +1715,7 @@ namespace OpenSim.Region.Framework.Scenes
 
             // Fudge factor.  It appears that if one clicks "go here" on a piece of ground, the go here request is
             // always slightly higher than the actual terrain height.
-            // FIXME: This constrains NOC movements as well, so should be somewhere else.
+            // FIXME: This constrains NPC movements as well, so should be somewhere else.
             if (pos.Z - terrainHeight < 0.2)
                 pos.Z = terrainHeight;
 
@@ -1727,6 +1731,21 @@ namespace OpenSim.Region.Framework.Scenes
             MovingToTarget = true;
             MoveToPositionTarget = pos;
 
+            // Rotate presence around the z-axis to point in same direction as movement.
+            // Ignore z component of vector
+            Vector3 localVectorToTarget3D = pos - AbsolutePosition;
+            Vector3 localVectorToTarget2D = new Vector3((float)(localVectorToTarget3D.X), (float)(localVectorToTarget3D.Y), 0f);
+
+//            m_log.DebugFormat("[SCENE PRESENCE]: Local vector to target is {0}", localVectorToTarget2D);
+
+            // Calculate the yaw.
+            Vector3 angle = new Vector3(0, 0, (float)(Math.Atan2(localVectorToTarget2D.Y, localVectorToTarget2D.X)));
+
+//            m_log.DebugFormat("[SCENE PRESENCE]: Angle is {0}", angle);
+
+            Rotation = Quaternion.CreateFromEulers(angle);
+//            m_log.DebugFormat("[SCENE PRESENCE]: Body rot for {0} set to {1}", Name, Rotation);
+
             Vector3 agent_control_v3 = new Vector3();
             HandleMoveToTargetUpdate(ref agent_control_v3);
             AddNewMovement(agent_control_v3);

OpenSim/Region/OptionalModules/World/NPC/Tests/NPCModuleTests.cs

@@ -182,18 +182,21 @@ namespace OpenSim.Region.OptionalModules.World.NPC.Tests
             scene.Update();
             Assert.That(npc.AbsolutePosition, Is.EqualTo(startPos));
 
-            Vector3 targetPos = startPos + new Vector3(0, 0, 10);
+            Vector3 targetPos = startPos + new Vector3(0, 10, 0);
             npcModule.MoveToTarget(npc.UUID, scene, targetPos, false, false);
 
             Assert.That(npc.AbsolutePosition, Is.EqualTo(startPos));
+            //Assert.That(npc.Rotation, Is.EqualTo(new Quaternion(0, 0, 0.7071068f, 0.7071068f)));
+            Assert.That(
+                npc.Rotation, new QuaternionToleranceConstraint(new Quaternion(0, 0, 0.7071068f, 0.7071068f), 0.000001));
 
             scene.Update();
 
             // We should really check the exact figure.
             Assert.That(npc.AbsolutePosition.X, Is.EqualTo(startPos.X));
-            Assert.That(npc.AbsolutePosition.Y, Is.EqualTo(startPos.Y));
+            Assert.That(npc.AbsolutePosition.Y, Is.GreaterThan(startPos.Y));
-            Assert.That(npc.AbsolutePosition.Z, Is.GreaterThan(startPos.Z));
+            Assert.That(npc.AbsolutePosition.Z, Is.EqualTo(startPos.Z));
-            Assert.That(npc.AbsolutePosition.Z, Is.LessThan(targetPos.Z));
+            Assert.That(npc.AbsolutePosition.Z, Is.LessThan(targetPos.X));
 
             for (int i = 0; i < 10; i++)
                 scene.Update();
@@ -208,6 +211,11 @@ namespace OpenSim.Region.OptionalModules.World.NPC.Tests
             targetPos = startPos + new Vector3(10, 0, 0);
             npcModule.MoveToTarget(npc.UUID, scene, targetPos, false, false);
 
+            Assert.That(npc.AbsolutePosition, Is.EqualTo(startPos));
+//            Assert.That(npc.Rotation, Is.EqualTo(new Quaternion(0, 0, 0, 1)));
+            Assert.That(
+                npc.Rotation, new QuaternionToleranceConstraint(new Quaternion(0, 0, 0, 1), 0.000001));
+
             scene.Update();
 
             // We should really check the exact figure.

OpenSim/Tests/Common/QuaternionToleranceConstraint.cs

@@ -0,0 +1,82 @@
+/*
+ * 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 copyright
+ *       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 OpenMetaverse;
+using NUnit.Framework;
+using NUnit.Framework.Constraints;
+
+namespace OpenSim.Tests.Common
+{
+    public class QuaternionToleranceConstraint : ANumericalToleranceConstraint
+    {
+        private Quaternion _baseValue;
+        private Quaternion _valueToBeTested;
+
+        public QuaternionToleranceConstraint(Quaternion baseValue, double tolerance) : base(tolerance)
+        {
+            _baseValue = baseValue;
+        }
+
+        /// <summary>
+        /// Test whether the constraint is satisfied by a given value
+        /// </summary>
+        /// <param name="valueToBeTested">The value to be tested</param>
+        /// <returns>
+        /// True for success, false for failure
+        /// </returns>
+        public override bool Matches(object valueToBeTested)
+        {
+            if (valueToBeTested == null)
+            {
+                throw new ArgumentException("Constraint cannot be used upon null values.");
+            }
+            if (valueToBeTested.GetType() != typeof (Quaternion))
+            {
+                throw new ArgumentException("Constraint cannot be used upon non quaternion values.");
+            }
+
+            _valueToBeTested = (Quaternion)valueToBeTested;
+
+            return (IsWithinDoubleConstraint(_valueToBeTested.X, _baseValue.X) &&
+                    IsWithinDoubleConstraint(_valueToBeTested.Y, _baseValue.Y) &&
+                    IsWithinDoubleConstraint(_valueToBeTested.Z, _baseValue.Z) &&
+                    IsWithinDoubleConstraint(_valueToBeTested.W, _baseValue.W));
+        }
+
+        public override void WriteDescriptionTo(MessageWriter writer)
+        {
+            writer.WriteExpectedValue(
+                string.Format("A value {0} within tolerance of plus or minus {1}", _baseValue, _tolerance));
+        }
+
+        public override void WriteActualValueTo(MessageWriter writer)
+        {
+            writer.WriteActualValue(_valueToBeTested);
+        }
+    }
+}