Another algorithm for AngularVerticalAttraction. This one Takes into account all rotations before it and makes the corrections more close to the time that sl does.

Signed-off-by: Robert Adams <Robert.Adams@intel.com>

OpenSim/Region/Physics/BulletSPlugin/BSDynamics.cs

@@ -1358,6 +1358,28 @@ namespace OpenSim.Region.Physics.BulletSPlugin
             // If vertical attaction timescale is reasonable
             if (enableAngularVerticalAttraction && m_verticalAttractionTimescale < m_verticalAttractionCutoff)
             {
+                //Another formula to try got from :
+                //http://answers.unity3d.com/questions/10425/how-to-stabilize-angular-motion-alignment-of-hover.html
+                Vector3 VehicleUpAxis = Vector3.UnitZ *VehicleOrientation;
+                //Flipping what was originally a timescale into a speed variable and then multiplying it by 2 since only computing half
+                //the distance between the angles.
+                float VerticalAttractionSpeed=(1/m_verticalAttractionTimescale)*2.0f;
+                //making a prediction of where the up axis will be when this is applied rather then where it is now this makes for a smoother
+                //adjustment and less fighting between the various forces
+                Vector3 predictedUp = VehicleUpAxis * Quaternion.CreateFromAxisAngle(VehicleRotationalVelocity, 0f);
+                //this is only half the distance to the target so it will take 2 seconds to complete the turn.
+                Vector3 torqueVector = Vector3.Cross(predictedUp, Vector3.UnitZ);
+                //Scaling vector by our timescale since it is an acceleration it is r/s^2 or radians a timescale squared
+                Vector3 vertContributionV=torqueVector * VerticalAttractionSpeed *VerticalAttractionSpeed;
+                VehicleRotationalVelocity += vertContributionV;
+                 VDetailLog("{0},  MoveAngular,verticalAttraction,UpAxis={1},PredictedUp={2},torqueVector={3},contrib={4}",
+                                ControllingPrim.LocalID,
+                                VehicleUpAxis,
+                                predictedUp,
+                                torqueVector,
+                                vertContributionV);
+                //=====================================================================
+                /*
                 // Possible solution derived from a discussion at:
                 // http://stackoverflow.com/questions/14939657/computing-vector-from-quaternion-works-computing-quaternion-from-vector-does-no
 
@@ -1392,6 +1414,7 @@ namespace OpenSim.Region.Physics.BulletSPlugin
                                 differenceAngle,
                                 correctionRotation,
                                 vertContributionV);
+                 */
 
                 // ===================================================================
                 /*