BulletSim: many changes to tune vehicles for BulletSim.

The problem left is that the vehicle sitting on something needs
to press down for gravity and what its sitting on pushes up
so the vehicle does not penetrate. The effect is Bullet calculates
a lot of random angular motion for the vehicle. Various schemes
of damping and zeroing has not resolved the problem.

OpenSim/Region/Physics/BulletSPlugin/BSDynamics.cs

@@ -54,10 +54,15 @@ namespace OpenSim.Region.Physics.BulletSPlugin
 {
     public sealed class BSDynamics
     {
+        private static string LogHeader = "[BULLETSIM VEHICLE]";
+
         private BSScene PhysicsScene { get; set; }
         // the prim this dynamic controller belongs to
         private BSPrim Prim { get; set; }
 
+        // mass of the vehicle fetched each time we're calles
+        private float m_vehicleMass;
+
         // Vehicle properties
         public Vehicle Type { get; set; }
 
@@ -516,9 +521,31 @@ namespace OpenSim.Region.Physics.BulletSPlugin
                 // Friction effects are handled by this vehicle code
                 BulletSimAPI.SetFriction2(Prim.PhysBody.ptr, 0f);
                 BulletSimAPI.SetHitFraction2(Prim.PhysBody.ptr, 0f);
+
+                // BulletSimAPI.SetAngularDamping2(Prim.PhysBody.ptr, 0.8f);
+
+                VDetailLog("{0},BSDynamics.Refresh,zeroingFriction and adding damping", Prim.LocalID);
             }
         }
 
+        public bool RemoveBodyDependencies(BSPhysObject prim)
+        {
+            // If active, we need to add our properties back when the body is rebuilt.
+            return IsActive;
+        }
+
+        public void RestoreBodyDependencies(BSPhysObject prim)
+        {
+            if (Prim.LocalID != prim.LocalID)
+            {
+                // The call should be on us by our prim. Error if not.
+                PhysicsScene.Logger.ErrorFormat("{0} RestoreBodyDependencies: called by not my prim. passedLocalID={1}, vehiclePrimLocalID={2}",
+                                LogHeader, prim.LocalID, Prim.LocalID);
+                return;
+            }
+            Refresh();
+        }
+
         // One step of the vehicle properties for the next 'pTimestep' seconds.
         internal void Step(float pTimestep)
         {
@@ -533,16 +560,26 @@ namespace OpenSim.Region.Physics.BulletSPlugin
             // m_lastLinearVelocityVector = Prim.ForceVelocity * Quaternion.Inverse(Prim.ForceOrientation);        // DEBUG:
             // END DEBUG
 
-            MoveLinear(pTimestep);
+            m_vehicleMass = Prim.Linkset.LinksetMass;
-            MoveAngular(pTimestep);
-            LimitRotation(pTimestep);
 
-            // DEBUG: Trying to figure out why Bullet goes crazy when the root prim is moved.
+            MoveLinear(pTimestep);
-            // BulletSimAPI.SetInterpolationVelocity2(Prim.BSBody.ptr, m_newVelocity, m_lastAngularVelocity); // DEBUG DEBUG DEBUG
+            // Commented out for debug
+            MoveAngular(pTimestep);
+            // Prim.ApplyTorqueImpulse(-Prim.RotationalVelocity * m_vehicleMass, false);    // DEBUG DEBUG
+            // Prim.ForceRotationalVelocity = -Prim.RotationalVelocity;    // DEBUG DEBUG
+
+            LimitRotation(pTimestep);
 
             // remember the position so next step we can limit absolute movement effects
             m_lastPositionVector = Prim.ForcePosition;
 
+            VDetailLog("{0},BSDynamics.Step,frict={1},grav={2},inertia={3},mass={4}",        // DEBUG DEBUG
+                                    Prim.LocalID, 
+                                    BulletSimAPI.GetFriction2(Prim.PhysBody.ptr),
+                                    BulletSimAPI.GetGravity2(Prim.PhysBody.ptr),
+                                    Prim.Inertia,
+                                    m_vehicleMass
+                                    );
             VDetailLog("{0},BSDynamics.Step,done,pos={1},force={2},velocity={3},angvel={4}",
                     Prim.LocalID, Prim.ForcePosition, Prim.Force, Prim.ForceVelocity, Prim.RotationalVelocity);
         }// end Step
@@ -555,25 +592,26 @@ namespace OpenSim.Region.Physics.BulletSPlugin
             // m_lastLinearVelocityVector is the current speed we are moving in that direction
             if (m_linearMotorDirection.LengthSquared() > 0.001f)
             {
-                Vector3 origDir = m_linearMotorDirection;
+                Vector3 origDir = m_linearMotorDirection;       // DEBUG
-                Vector3 origVel = m_lastLinearVelocityVector;
+                Vector3 origVel = m_lastLinearVelocityVector;   // DEBUG
+                // DEBUG: the vehicle velocity rotated to be relative to vehicle coordinates for comparison
                 Vector3 vehicleVelocity = Prim.ForceVelocity * Quaternion.Inverse(Prim.ForceOrientation);   // DEBUG
 
-                // add drive to body
+                // Add (desiredVelocity - lastAppliedVelocity) / howLongItShouldTakeToComplete
                 Vector3 addAmount = (m_linearMotorDirection - m_lastLinearVelocityVector)/(m_linearMotorTimescale) * pTimestep;
-                // lastLinearVelocityVector is the current body velocity vector
                 m_lastLinearVelocityVector += addAmount;
 
                 float decayFactor = (1.0f / m_linearMotorDecayTimescale) * pTimestep;
                 m_linearMotorDirection *= (1f - decayFactor);
 
-                Vector3 frictionFactor = (Vector3.One / m_linearFrictionTimescale) * pTimestep;
-                m_lastLinearVelocityVector *= (Vector3.One - frictionFactor);
-
                 // Rotate new object velocity from vehicle relative to world coordinates
                 m_newVelocity = m_lastLinearVelocityVector * Prim.ForceOrientation;
 
-                VDetailLog("{0},MoveLinear,nonZero,origdir={1},origvel={2},vehVel={3},add={4},decay={5},frict={6},lmDir={7},lmVel={8},newVel={9}",
+                // Apply friction for next time
+                Vector3 frictionFactor = (Vector3.One / m_linearFrictionTimescale) * pTimestep;
+                m_lastLinearVelocityVector *= (Vector3.One - frictionFactor);
+
+                VDetailLog("{0},MoveLinear,nonZero,origlmDir={1},origlvVel={2},vehVel={3},add={4},decay={5},frict={6},lmDir={7},lvVec={8},newVel={9}",
                                 Prim.LocalID, origDir, origVel, vehicleVelocity, addAmount, decayFactor, frictionFactor, 
                                 m_linearMotorDirection, m_lastLinearVelocityVector, m_newVelocity);
             }
@@ -607,7 +645,7 @@ namespace OpenSim.Region.Physics.BulletSPlugin
             // If below the terrain, move us above the ground a little.
             float terrainHeight = Prim.PhysicsScene.TerrainManager.GetTerrainHeightAtXYZ(pos);
             // Taking the rotated size doesn't work here because m_prim.Size is the size of the root prim and not the linkset.
-            //     Need to add a m_prim.LinkSet.Size similar to m_prim.LinkSet.Mass.
+            //     TODO: Add a m_prim.LinkSet.Size similar to m_prim.LinkSet.Mass.
             // Vector3 rotatedSize = m_prim.Size * m_prim.ForceOrientation;
             // if (rotatedSize.Z < terrainHeight)
             if (pos.Z < terrainHeight)
@@ -638,13 +676,15 @@ namespace OpenSim.Region.Physics.BulletSPlugin
 
                 if ((m_flags & VehicleFlag.HOVER_UP_ONLY) != 0)
                 {
-                    // If body is aready heigher, use its height as target height
+                    // If body is already heigher, use its height as target height
-                    if (pos.Z > m_VhoverTargetHeight) m_VhoverTargetHeight = pos.Z;
+                    if (pos.Z > m_VhoverTargetHeight)
+                        m_VhoverTargetHeight = pos.Z;
                 }
                 if ((m_flags & VehicleFlag.LOCK_HOVER_HEIGHT) != 0)
                 {
-                    if ((pos.Z - m_VhoverTargetHeight) > .2 || (pos.Z - m_VhoverTargetHeight) < -.2)
+                    if (Math.Abs(pos.Z - m_VhoverTargetHeight) > 0.2f)
                     {
+                        pos.Z = m_VhoverTargetHeight;
                         Prim.ForcePosition = pos;
                     }
                 }
@@ -709,25 +749,28 @@ namespace OpenSim.Region.Physics.BulletSPlugin
                 }
             }
 
-            // Limit absolute vertical change
+            #region downForce
-            float Zchange = Math.Abs(posChange.Z);
+            Vector3 downForce = Vector3.Zero;
+
             if ((m_flags & (VehicleFlag.LIMIT_MOTOR_UP)) != 0)
             {
-                if (Zchange > .3)
+                // If the vehicle is motoring into the sky, get it going back down.
-                    grav.Z = (float)(grav.Z * 3);
+                // Is this an angular force or both linear and angular??
-                if (Zchange > .15)
+                float distanceAboveGround = pos.Z - terrainHeight;
-                    grav.Z = (float)(grav.Z * 2);
+                if (distanceAboveGround > 2f)
-                if (Zchange > .75)
+                {
-                    grav.Z = (float)(grav.Z * 1.5);
+                    // downForce = new Vector3(0, 0, (-distanceAboveGround / m_bankingTimescale) * pTimestep);
-                if (Zchange > .05)
+                    // downForce = new Vector3(0, 0, -distanceAboveGround / m_bankingTimescale);
-                    grav.Z = (float)(grav.Z * 1.25);
+                    downForce = new Vector3(0, 0, -distanceAboveGround);
-                if (Zchange > .025)
-                    grav.Z = (float)(grav.Z * 1.125);
-                float postemp = (pos.Z - terrainHeight);
-                if (postemp > 2.5f)
-                    grav.Z = (float)(grav.Z * 1.037125);
-                VDetailLog("{0},MoveLinear,limitMotorUp,grav={1}", Prim.LocalID, grav);
                 }
+                // TODO: this calculation is all wrong. From the description at
+                //     (http://wiki.secondlife.com/wiki/Category:LSL_Vehicle), the downForce
+                //     has a decay factor. This says this force should
+                //     be computed with a motor.
+                VDetailLog("{0},MoveLinear,limitMotorUp,distAbove={1},downForce={2}", 
+                                    Prim.LocalID, distanceAboveGround, downForce);
+            }
+            #endregion // downForce
 
             // If not changing some axis, reduce out velocity
             if ((m_flags & (VehicleFlag.NO_X)) != 0)
@@ -737,13 +780,28 @@ namespace OpenSim.Region.Physics.BulletSPlugin
             if ((m_flags & (VehicleFlag.NO_Z)) != 0)
                 m_newVelocity.Z = 0;
 
-            // Apply velocity
+            // Clamp REALLY high or low velocities
-            Prim.ForceVelocity = m_newVelocity;
+            if (m_newVelocity.LengthSquared() > 1e6f)
-            // Prim.AddForce(m_newVelocity * Prim.Linkset.LinksetMass, false);
+            {
-            Prim.AddForce(grav * Prim.Linkset.LinksetMass, false);
+                m_newVelocity /= m_newVelocity.Length();
+                m_newVelocity *= 1000f;
+            }
+            else if (m_newVelocity.LengthSquared() < 1e-6f)
+                m_newVelocity = Vector3.Zero;
 
-            VDetailLog("{0},MoveLinear,done,lmDir={1},lmVel={2},newVel={3},grav={4}",
+            // Stuff new linear velocity into the vehicle
-                    Prim.LocalID, m_linearMotorDirection, m_lastLinearVelocityVector, m_newVelocity, grav);
+            Prim.ForceVelocity = m_newVelocity;
+            // Prim.ApplyForceImpulse((m_newVelocity - Prim.Velocity) * m_vehicleMass, false);    // DEBUG DEBUG
+
+            Vector3 totalDownForce = downForce + grav;
+            if (totalDownForce != Vector3.Zero)
+            {
+                Prim.AddForce(totalDownForce * m_vehicleMass, false);
+                // Prim.ApplyForceImpulse(totalDownForce * m_vehicleMass, false);
+            }
+
+            VDetailLog("{0},MoveLinear,done,lmDir={1},lmVel={2},newVel={3},primVel={4},totalDown={5}",
+                    Prim.LocalID, m_linearMotorDirection, m_lastLinearVelocityVector, m_newVelocity, Prim.Velocity, totalDownForce);
 
         } // end MoveLinear()
 
@@ -765,7 +823,7 @@ namespace OpenSim.Region.Physics.BulletSPlugin
                 Vector3 origDir = m_angularMotorDirection;
 
                 //       new velocity    +=                      error                       /  (  time to get there   / step interval)
-                //                             requested speed     -    last motor speed
+                //                           requested direction   - current vehicle direction
                 m_angularMotorVelocity += (m_angularMotorDirection - m_angularMotorVelocity) /  (m_angularMotorTimescale / pTimestep);
                 // decay requested direction
                 m_angularMotorDirection *= (1.0f - (pTimestep * 1.0f/m_angularMotorDecayTimescale));
@@ -784,10 +842,11 @@ namespace OpenSim.Region.Physics.BulletSPlugin
             Vector3 deflection = Vector3.Zero;
             Vector3 banking = Vector3.Zero;
 
+            // If vertical attaction timescale is reasonable and we applied an angular force last time...
             if (m_verticalAttractionTimescale < 300 && m_lastAngularVelocity != Vector3.Zero)
             {
                 float VAservo = pTimestep * 0.2f / m_verticalAttractionTimescale;
-                if (Prim.Linkset.LinksetIsColliding)
+                if (Prim.IsColliding)
                     VAservo = pTimestep * 0.05f / (m_verticalAttractionTimescale);
 
                 VAservo *= (m_verticalAttractionEfficiency * m_verticalAttractionEfficiency);
@@ -806,7 +865,7 @@ namespace OpenSim.Region.Physics.BulletSPlugin
                     verticalError.X = 2.0f - verticalError.X;
                     verticalError.Y = 2.0f - verticalError.Y;
                 }
-                // scale it by VAservo
+                // scale it by VAservo (timestep and timescale)
                 verticalError = verticalError * VAservo;
 
                 // As the body rotates around the X axis, then verticalError.Y increases; Rotated around Y
@@ -822,25 +881,30 @@ namespace OpenSim.Region.Physics.BulletSPlugin
                 vertattr.X += bounce * angularVelocity.X;
                 vertattr.Y += bounce * angularVelocity.Y;
 
-                VDetailLog("{0},MoveAngular,verticalAttraction,verticalError={1},bounce={2},vertattr={3}",
+                VDetailLog("{0},MoveAngular,verticalAttraction,VAservo={1},effic={2},verticalError={3},bounce={4},vertattr={5}",
-                            Prim.LocalID, verticalError, bounce, vertattr);
+                            Prim.LocalID, VAservo, m_verticalAttractionEfficiency, verticalError, bounce, vertattr);
 
             }
             #endregion // Vertical attactor
 
             #region Deflection
 
-            //Forward is the prefered direction, but if the reference frame has changed, we need to take this into account as well
             if (m_angularDeflectionEfficiency != 0)
             {
-                Vector3 preferredAxisOfMotion =
+                // Compute a scaled vector that points in the preferred axis (X direction)
+                Vector3 scaledDefaultDirection =
                     new Vector3((pTimestep * 10 * (m_angularDeflectionEfficiency / m_angularDeflectionTimescale)), 0, 0);
-                preferredAxisOfMotion *= Quaternion.Add(Prim.ForceOrientation, m_referenceFrame);
+                // Adding the current vehicle orientation and reference frame displaces the orientation to the frame.
+                // Rotate the scaled default axix relative to the actual vehicle direction giving where it should point.
+                Vector3 preferredAxisOfMotion = scaledDefaultDirection * Quaternion.Add(Prim.ForceOrientation, m_referenceFrame);
 
+                // Scale by efficiency and timescale
                 deflection = (preferredAxisOfMotion * (m_angularDeflectionEfficiency) / m_angularDeflectionTimescale) * pTimestep;
 
                 VDetailLog("{0},MoveAngular,Deflection,perfAxis={1},deflection={2}", 
                                         Prim.LocalID, preferredAxisOfMotion, deflection);
+                // This deflection computation is not correct.
+                deflection = Vector3.Zero;
             }
 
             #endregion
@@ -875,7 +939,7 @@ namespace OpenSim.Region.Physics.BulletSPlugin
                 }
                 else
                     banking.Z += (effSquared*(mult*mix))*(m_angularMotorVelocity.X) * 4;
-                if (!Prim.Linkset.LinksetIsColliding && Math.Abs(m_angularMotorVelocity.X) > mix)
+                if (!Prim.IsColliding && Math.Abs(m_angularMotorVelocity.X) > mix)
                     //If they are colliding, we probably shouldn't shove the prim around... probably
                 {
                     float angVelZ = m_angularMotorVelocity.X*-1;
@@ -904,6 +968,40 @@ namespace OpenSim.Region.Physics.BulletSPlugin
             // Sum velocities
             m_lastAngularVelocity = m_angularMotorVelocity + vertattr + banking + deflection;
 
+            #region Linear Motor Offset
+
+            //Offset section
+            if (m_linearMotorOffset != Vector3.Zero)
+            {
+                //Offset of linear velocity doesn't change the linear velocity,
+                //   but causes a torque to be applied, for example...
+                //
+                //      IIIII     >>>   IIIII
+                //      IIIII     >>>    IIIII
+                //      IIIII     >>>     IIIII
+                //          ^
+                //          |  Applying a force at the arrow will cause the object to move forward, but also rotate
+                //
+                //
+                // The torque created is the linear velocity crossed with the offset
+
+                // NOTE: this computation does should be in the linear section
+                //    because there we know the impulse being applied.
+                Vector3 torqueFromOffset = Vector3.Zero;
+                // torqueFromOffset = Vector3.Cross(m_linearMotorOffset, appliedImpulse);
+                if (float.IsNaN(torqueFromOffset.X))
+                    torqueFromOffset.X = 0;
+                if (float.IsNaN(torqueFromOffset.Y))
+                    torqueFromOffset.Y = 0;
+                if (float.IsNaN(torqueFromOffset.Z))
+                    torqueFromOffset.Z = 0;
+                torqueFromOffset *= m_vehicleMass;
+                Prim.ApplyTorqueImpulse(torqueFromOffset, true);
+                VDetailLog("{0},BSDynamic.MoveAngular,motorOffset,applyTorqueImpulse={1}", Prim.LocalID, torqueFromOffset);
+            }
+
+            #endregion
+
             if ((m_flags & (VehicleFlag.NO_DEFLECTION_UP)) != 0)
             {
                 m_lastAngularVelocity.X = 0;
@@ -914,25 +1012,25 @@ namespace OpenSim.Region.Physics.BulletSPlugin
             if (m_lastAngularVelocity.ApproxEquals(Vector3.Zero, 0.01f))
             {
                 m_lastAngularVelocity = Vector3.Zero; // Reduce small value to zero.
-                VDetailLog("{0},MoveAngular,zeroSmallValues,lastAngular={1}", Prim.LocalID, m_lastAngularVelocity);
+                Prim.ZeroAngularMotion(true);
+                VDetailLog("{0},MoveAngular,zeroAngularMotion,lastAngular={1}", Prim.LocalID, m_lastAngularVelocity);
             }
+            else
+            {
+                // Apply to the body.
+                // The above calculates the absolute angular velocity needed. Angular velocity is massless.
+                // Since we are stuffing the angular velocity directly into the object, the computed
+                //     velocity needs to be scaled by the timestep.
+                Vector3 applyAngularForce = ((m_lastAngularVelocity * pTimestep) - Prim.ForceRotationalVelocity);
+                Prim.ForceRotationalVelocity = applyAngularForce;
 
-            // Apply to the body
+                // Decay the angular movement for next time
-            // The above calculates the absolute angular velocity needed
-            // Prim.ForceRotationalVelocity = m_lastAngularVelocity;
-
-            // Apply a force to overcome current angular velocity
-            Vector3 applyAngularForce = (m_lastAngularVelocity - Prim.ForceRotationalVelocity) * Prim.Linkset.LinksetMass;
-            // Vector3 applyAngularForce = (m_lastAngularVelocity - Prim.ForceRotationalVelocity);
-            // Prim.AddAngularForce(applyAngularForce, false);
-            Prim.ApplyTorqueImpulse(applyAngularForce, false);
-
-             // Apply friction for next time
                 Vector3 decayamount = (Vector3.One / m_angularFrictionTimescale) * pTimestep;
                 m_lastAngularVelocity *= Vector3.One - decayamount;
 
-            VDetailLog("{0},MoveAngular,done,applyAForce={1},decay={2},lastAngular={3}", 
+                VDetailLog("{0},MoveAngular,done,newRotVel={1},decay={2},lastAngular={3}", 
                                     Prim.LocalID, applyAngularForce, decayamount, m_lastAngularVelocity);
+            }
         } //end MoveAngular
 
         internal void LimitRotation(float timestep)