Fixes Mantis #3260. Thank you kindly, MCortez for a patch that:

llSetHoverHeight() should not clamp the x/y position of an object the way MoveTo does, 
and it should recalculate the absolute height to hover at as an object moves to reflect 
the current ground/water height under it.
Correctly implementing required adjusting the Physics interfaces and implementing at 
the physics plug-in level. The attached is a patch that correctly implements 
llSetHoverHeight() including updates to the ODE physics plug-in.

1 files changed, 25 insertions, 1 deletions

diff --git a/OpenSim/Region/Physics/Manager/PhysicsActor.cs b/OpenSim/Region/Physics/Manager/PhysicsActor.cs
index 0f75c46..c4bb889 100644
--- a/OpenSim/Region/Physics/Manager/PhysicsActor.cs
+++ b/OpenSim/Region/Physics/Manager/PhysicsActor.cs
@@ -44,6 +44,14 @@ namespace OpenSim.Region.Physics.Manager
         Ground = 3
     }
 
+    public enum PIDHoverType
+    {
+        Ground
+        , GroundAndWater
+        , Water
+        , Absolute
+    }
+
     public class CollisionEventUpdate : EventArgs
     {
         // Raising the event on the object, so don't need to provide location..  further up the tree knows that info.
@@ -204,9 +212,20 @@ namespace OpenSim.Region.Physics.Manager
         public abstract PhysicsVector RotationalVelocity { get; set; }
         public abstract bool Kinematic { get; set; }
         public abstract float Buoyancy { get; set; }
+
+        // Used for MoveTo
         public abstract PhysicsVector PIDTarget { set;}
-        public abstract bool PIDActive { set;}
+        public abstract bool  PIDActive { set;}
         public abstract float PIDTau { set; }
+
+        // Used for llSetHoverHeight and maybe vehicle height
+        // Hover Height will override MoveTo target's Z
+        public abstract bool PIDHoverActive { set;}
+        public abstract float PIDHoverHeight { set;}
+        public abstract PIDHoverType PIDHoverType { set;}
+        public abstract float PIDHoverTau { set;}
+
+
         public abstract void AddForce(PhysicsVector force, bool pushforce);
         public abstract void AddAngularForce(PhysicsVector force, bool pushforce);
         public abstract void SetMomentum(PhysicsVector momentum);
@@ -430,6 +449,11 @@ namespace OpenSim.Region.Physics.Manager
         public override bool PIDActive { set { return; } }
         public override float PIDTau { set { return; } }
 
+        public override float PIDHoverHeight { set { return; } }
+        public override bool PIDHoverActive { set { return; } }
+        public override PIDHoverType PIDHoverType { set { return; } }
+        public override float PIDHoverTau { set { return; } }
+
         public override void SetMomentum(PhysicsVector momentum)
         {
         }