Fix sp.AbsolutePosition when agent is sitting on a child prim, which in turns fixes llDetectedPos(), llGetLinkPrimitiveParams() and similar functions.

Add regression test for this case.
In relation to http://opensimulator.org/mantis/view.php?id=7043

2 files changed, 64 insertions, 4 deletions

diff --git a/OpenSim/Region/Framework/Scenes/ScenePresence.cs b/OpenSim/Region/Framework/Scenes/ScenePresence.cs
index a0b4019..6e613a7 100644
--- a/OpenSim/Region/Framework/Scenes/ScenePresence.cs
+++ b/OpenSim/Region/Framework/Scenes/ScenePresence.cs
@@ -538,7 +538,7 @@ namespace OpenSim.Region.Framework.Scenes
                     SceneObjectPart sitPart = ParentPart;
 
                     if (sitPart != null)
-                        return sitPart.AbsolutePosition + (m_pos * sitPart.GetWorldRotation());
+                        return sitPart.ParentGroup.AbsolutePosition + (m_pos * sitPart.GetWorldRotation());
                 }
                 
                 return m_pos;
diff --git a/OpenSim/Region/Framework/Scenes/Tests/ScenePresenceSitTests.cs b/OpenSim/Region/Framework/Scenes/Tests/ScenePresenceSitTests.cs
index dcdec5c..03ea969 100644
--- a/OpenSim/Region/Framework/Scenes/Tests/ScenePresenceSitTests.cs
+++ b/OpenSim/Region/Framework/Scenes/Tests/ScenePresenceSitTests.cs
@@ -73,6 +73,7 @@ namespace OpenSim.Region.Framework.Scenes.Tests
             Assert.That(part.GetSittingAvatarsCount(), Is.EqualTo(0));
             Assert.That(part.GetSittingAvatars(), Is.Null);
             Assert.That(m_sp.ParentID, Is.EqualTo(0));
+            Assert.AreEqual(startPos, m_sp.AbsolutePosition);
         }
 
         [Test]
@@ -87,10 +88,16 @@ namespace OpenSim.Region.Framework.Scenes.Tests
 
             SceneObjectPart part = SceneHelpers.AddSceneObject(m_scene).RootPart;
 
+            // We need to preserve this here because phys actor is removed by the sit.
+            Vector3 spPhysActorSize = m_sp.PhysicsActor.Size;
             m_sp.HandleAgentRequestSit(m_sp.ControllingClient, m_sp.UUID, part.UUID, Vector3.Zero);
 
             Assert.That(m_sp.PhysicsActor, Is.Null);
 
+            Assert.That(
+                m_sp.AbsolutePosition,
+                Is.EqualTo(part.AbsolutePosition + new Vector3(0, 0, spPhysActorSize.Z / 2)));
+
             Assert.That(part.SitTargetAvatar, Is.EqualTo(UUID.Zero));
             Assert.That(part.GetSittingAvatarsCount(), Is.EqualTo(1));
             HashSet<ScenePresence> sittingAvatars = part.GetSittingAvatars();
@@ -129,6 +136,36 @@ namespace OpenSim.Region.Framework.Scenes.Tests
         }
 
         [Test]
+        public void TestSitAndStandWithNoSitTargetChildPrim()
+        {
+            TestHelpers.InMethod();
+//            log4net.Config.XmlConfigurator.Configure();
+
+            // Make sure we're within range to sit
+            Vector3 startPos = new Vector3(1, 1, 1);
+            m_sp.AbsolutePosition = startPos;
+
+            SceneObjectPart part = SceneHelpers.AddSceneObject(m_scene, 2, m_sp.UUID, "part", 0x10).Parts[1];
+            part.OffsetPosition = new Vector3(2, 3, 4);
+
+            // We need to preserve this here because phys actor is removed by the sit.
+            Vector3 spPhysActorSize = m_sp.PhysicsActor.Size;
+            m_sp.HandleAgentRequestSit(m_sp.ControllingClient, m_sp.UUID, part.UUID, Vector3.Zero);
+
+            Assert.That(
+                m_sp.AbsolutePosition,
+                Is.EqualTo(part.AbsolutePosition + new Vector3(0, 0, spPhysActorSize.Z / 2)));
+
+            m_sp.StandUp();
+
+            Assert.That(part.SitTargetAvatar, Is.EqualTo(UUID.Zero));
+            Assert.That(part.GetSittingAvatarsCount(), Is.EqualTo(0));
+            Assert.That(part.GetSittingAvatars(), Is.Null);
+            Assert.That(m_sp.ParentID, Is.EqualTo(0));
+            Assert.That(m_sp.PhysicsActor, Is.Not.Null);
+        }
+
+        [Test]
         public void TestSitAndStandWithSitTarget()
         {
             TestHelpers.InMethod();
@@ -145,9 +182,32 @@ namespace OpenSim.Region.Framework.Scenes.Tests
 
             Assert.That(part.SitTargetAvatar, Is.EqualTo(m_sp.UUID));
             Assert.That(m_sp.ParentID, Is.EqualTo(part.LocalId));
-//            Assert.That(
-//                m_sp.AbsolutePosition,
-//                Is.EqualTo(part.AbsolutePosition + part.SitTargetPosition + ScenePresence.SIT_TARGET_ADJUSTMENT));
+
+            // This section is copied from ScenePresence.HandleAgentSit().  Correctness is not guaranteed.
+            Quaternion r = part.SitTargetOrientation;
+            double x, y, z, m;
+            m = r.X * r.X + r.Y * r.Y + r.Z * r.Z + r.W * r.W;
+
+            if (Math.Abs(1.0 - m) > 0.000001)
+            {
+                m = 1.0 / Math.Sqrt(m);
+                r.X *= (float)m;
+                r.Y *= (float)m;
+                r.Z *= (float)m;
+                r.W *= (float)m;
+            }
+
+            x = 2 * (r.X * r.Z + r.Y * r.W);
+            y = 2 * (-r.X * r.W + r.Y * r.Z);
+            z = -r.X * r.X - r.Y * r.Y + r.Z * r.Z + r.W * r.W;
+
+            Vector3 up = new Vector3((float)x, (float)y, (float)z);
+            Vector3 sitOffset = up * m_sp.Appearance.AvatarHeight * 0.02638f;
+            // End of copied section.
+
+            Assert.That(
+                m_sp.AbsolutePosition,
+                Is.EqualTo(part.AbsolutePosition + part.SitTargetPosition + sitOffset + ScenePresence.SIT_TARGET_ADJUSTMENT));
             Assert.That(m_sp.PhysicsActor, Is.Null);
 
             Assert.That(part.GetSittingAvatarsCount(), Is.EqualTo(1));