/*
 * 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.
 *

/* RA: June 14, 2011. Copied from ODEDynamics.cs and converted to
 * call the BulletSim system.
 */
/* Revised Aug, Sept 2009 by Kitto Flora. ODEDynamics.cs replaces
 * ODEVehicleSettings.cs. It and ODEPrim.cs are re-organised:
 * ODEPrim.cs contains methods dealing with Prim editing, Prim
 * characteristics and Kinetic motion.
 * ODEDynamics.cs contains methods dealing with Prim Physical motion
 * (dynamics) and the associated settings. Old Linear and angular
 * motors for dynamic motion have been replace with  MoveLinear()
 * and MoveAngular(); 'Physical' is used only to switch ODE dynamic
 * simualtion on/off; VEHICAL_TYPE_NONE/VEHICAL_TYPE_<other> is to
 * switch between 'VEHICLE' parameter use and general dynamics
 * settings use.
 */

using System;
using System.Collections.Generic;
using System.Reflection;
using System.Runtime.InteropServices;
using log4net;
using OpenMetaverse;
using OpenSim.Framework;
using OpenSim.Region.Physics.Manager;

namespace OpenSim.Region.Physics.BulletSPlugin
{
    public sealed class BSDynamics
    {
        private BSScene PhysicsScene { get; set; }
        // the prim this dynamic controller belongs to
        private BSPrim Prim { get; set; }

        // Vehicle properties
        public Vehicle Type { get; set; }

        // private Quaternion m_referenceFrame = Quaternion.Identity;   // Axis modifier
        private VehicleFlag m_flags = (VehicleFlag) 0;                  // Boolean settings:
                                                                        // HOVER_TERRAIN_ONLY
                                                                        // HOVER_GLOBAL_HEIGHT
                                                                        // NO_DEFLECTION_UP
                                                                        // HOVER_WATER_ONLY
                                                                        // HOVER_UP_ONLY
                                                                        // LIMIT_MOTOR_UP
                                                                        // LIMIT_ROLL_ONLY
        private Vector3 m_BlockingEndPoint = Vector3.Zero;
        private Quaternion m_RollreferenceFrame = Quaternion.Identity;
        private Quaternion m_referenceFrame = Quaternion.Identity;

        // Linear properties
        private Vector3 m_linearMotorDirection = Vector3.Zero;          // velocity requested by LSL, decayed by time
        private Vector3 m_linearMotorOffset = Vector3.Zero;             // the point of force can be offset from the center
        private Vector3 m_linearMotorDirectionLASTSET = Vector3.Zero;   // velocity requested by LSL
        private Vector3 m_newVelocity = Vector3.Zero;                   // velocity computed to be applied to body
        private Vector3 m_linearFrictionTimescale = Vector3.Zero;
        private float m_linearMotorDecayTimescale = 0;
        private float m_linearMotorTimescale = 0;
        private Vector3 m_lastLinearVelocityVector = Vector3.Zero;
        private Vector3 m_lastPositionVector = Vector3.Zero;
        // private bool m_LinearMotorSetLastFrame = false;
        // private Vector3 m_linearMotorOffset = Vector3.Zero;

        //Angular properties
        private Vector3 m_angularMotorDirection = Vector3.Zero;         // angular velocity requested by LSL motor
        // private int m_angularMotorApply = 0;                            // application frame counter
        private Vector3 m_angularMotorVelocity = Vector3.Zero;          // current angular motor velocity
        private float m_angularMotorTimescale = 0;                      // motor angular velocity ramp up rate
        private float m_angularMotorDecayTimescale = 0;                 // motor angular velocity decay rate
        private Vector3 m_angularFrictionTimescale = Vector3.Zero;      // body angular velocity  decay rate
        private Vector3 m_lastAngularVelocity = Vector3.Zero;           // what was last applied to body
        private Vector3 m_lastVertAttractor = Vector3.Zero;             // what VA was last applied to body

        //Deflection properties
        private float m_angularDeflectionEfficiency = 0;
        private float m_angularDeflectionTimescale = 0;
        private float m_linearDeflectionEfficiency = 0;
        private float m_linearDeflectionTimescale = 0;

        //Banking properties
        private float m_bankingEfficiency = 0;
        private float m_bankingMix = 0;
        private float m_bankingTimescale = 0;

        //Hover and Buoyancy properties
        private float m_VhoverHeight = 0f;
        private float m_VhoverEfficiency = 0f;
        private float m_VhoverTimescale = 0f;
        private float m_VhoverTargetHeight = -1.0f;     // if <0 then no hover, else its the current target height
        private float m_VehicleBuoyancy = 0f;           //KF: m_VehicleBuoyancy is set by VEHICLE_BUOYANCY for a vehicle.
                    // Modifies gravity. Slider between -1 (double-gravity) and 1 (full anti-gravity)
                    // KF: So far I have found no good method to combine a script-requested .Z velocity and gravity.
                    // Therefore only m_VehicleBuoyancy=1 (0g) will use the script-requested .Z velocity.

        //Attractor properties
        private float m_verticalAttractionEfficiency = 1.0f;        // damped
        private float m_verticalAttractionTimescale = 500f;         // Timescale > 300  means no vert attractor.

        public BSDynamics(BSScene myScene, BSPrim myPrim)
        {
            PhysicsScene = myScene;
            Prim = myPrim;
            Type = Vehicle.TYPE_NONE;
        }

        // Return 'true' if this vehicle is doing vehicle things
        public bool IsActive
        {
            get { return Type != Vehicle.TYPE_NONE; }
        }

        internal void ProcessFloatVehicleParam(Vehicle pParam, float pValue)
        {
            VDetailLog("{0},ProcessFloatVehicleParam,param={1},val={2}", Prim.LocalID, pParam, pValue);
            switch (pParam)
            {
                case Vehicle.ANGULAR_DEFLECTION_EFFICIENCY:
                    m_angularDeflectionEfficiency = Math.Max(pValue, 0.01f);
                    break;
                case Vehicle.ANGULAR_DEFLECTION_TIMESCALE:
                    m_angularDeflectionTimescale = Math.Max(pValue, 0.01f);
                    break;
                case Vehicle.ANGULAR_MOTOR_DECAY_TIMESCALE:
                    m_angularMotorDecayTimescale = Math.Max(pValue, 0.01f);
                    break;
                case Vehicle.ANGULAR_MOTOR_TIMESCALE:
                    m_angularMotorTimescale = Math.Max(pValue, 0.01f);
                    break;
                case Vehicle.BANKING_EFFICIENCY:
                    m_bankingEfficiency = Math.Max(-1f, Math.Min(pValue, 1f));
                    break;
                case Vehicle.BANKING_MIX:
                    m_bankingMix = Math.Max(pValue, 0.01f);
                    break;
                case Vehicle.BANKING_TIMESCALE:
                    m_bankingTimescale = Math.Max(pValue, 0.01f);
                    break;
                case Vehicle.BUOYANCY:
                    m_VehicleBuoyancy = Math.Max(-1f, Math.Min(pValue, 1f));
                    break;
                case Vehicle.HOVER_EFFICIENCY:
                    m_VhoverEfficiency = Math.Max(0f, Math.Min(pValue, 1f));
                    break;
                case Vehicle.HOVER_HEIGHT:
                    m_VhoverHeight = pValue;
                    break;
                case Vehicle.HOVER_TIMESCALE:
                    m_VhoverTimescale = Math.Max(pValue, 0.01f);
                    break;
                case Vehicle.LINEAR_DEFLECTION_EFFICIENCY:
                    m_linearDeflectionEfficiency = Math.Max(pValue, 0.01f);
                    break;
                case Vehicle.LINEAR_DEFLECTION_TIMESCALE:
                    m_linearDeflectionTimescale = Math.Max(pValue, 0.01f);
                    break;
                case Vehicle.LINEAR_MOTOR_DECAY_TIMESCALE:
                    m_linearMotorDecayTimescale = Math.Max(pValue, 0.01f);
                    break;
                case Vehicle.LINEAR_MOTOR_TIMESCALE:
                    m_linearMotorTimescale = Math.Max(pValue, 0.01f);
                    break;
                case Vehicle.VERTICAL_ATTRACTION_EFFICIENCY:
                    m_verticalAttractionEfficiency = Math.Max(0.1f, Math.Min(pValue, 1f));
                    break;
                case Vehicle.VERTICAL_ATTRACTION_TIMESCALE:
                    m_verticalAttractionTimescale = Math.Max(pValue, 0.01f);
                    break;

                // These are vector properties but the engine lets you use a single float value to
                // set all of the components to the same value
                case Vehicle.ANGULAR_FRICTION_TIMESCALE:
                    m_angularFrictionTimescale = new Vector3(pValue, pValue, pValue);
                    break;
                case Vehicle.ANGULAR_MOTOR_DIRECTION:
                    m_angularMotorDirection = new Vector3(pValue, pValue, pValue);
                    // m_angularMotorApply = 100;
                    break;
                case Vehicle.LINEAR_FRICTION_TIMESCALE:
                    m_linearFrictionTimescale = new Vector3(pValue, pValue, pValue);
                    break;
                case Vehicle.LINEAR_MOTOR_DIRECTION:
                    m_linearMotorDirection = new Vector3(pValue, pValue, pValue);
                    m_linearMotorDirectionLASTSET = new Vector3(pValue, pValue, pValue);
                    break;
                case Vehicle.LINEAR_MOTOR_OFFSET:
                    m_linearMotorOffset = new Vector3(pValue, pValue, pValue);
                    break;

            }
        }//end ProcessFloatVehicleParam

        internal void ProcessVectorVehicleParam(Vehicle pParam, Vector3 pValue)
        {
            VDetailLog("{0},ProcessVectorVehicleParam,param={1},val={2}", Prim.LocalID, pParam, pValue);
            switch (pParam)
            {
                case Vehicle.ANGULAR_FRICTION_TIMESCALE:
                    m_angularFrictionTimescale = new Vector3(pValue.X, pValue.Y, pValue.Z);
                    break;
                case Vehicle.ANGULAR_MOTOR_DIRECTION:
                    // Limit requested angular speed to 2 rps= 4 pi rads/sec
                    pValue.X = Math.Max(-12.56f, Math.Min(pValue.X, 12.56f));
                    pValue.Y = Math.Max(-12.56f, Math.Min(pValue.Y, 12.56f));
                    pValue.Z = Math.Max(-12.56f, Math.Min(pValue.Z, 12.56f));
                    m_angularMotorDirection = new Vector3(pValue.X, pValue.Y, pValue.Z);
                    // m_angularMotorApply = 100;
                    break;
                case Vehicle.LINEAR_FRICTION_TIMESCALE:
                    m_linearFrictionTimescale = new Vector3(pValue.X, pValue.Y, pValue.Z);
                    break;
                case Vehicle.LINEAR_MOTOR_DIRECTION:
                    m_linearMotorDirection = new Vector3(pValue.X, pValue.Y, pValue.Z);
                    m_linearMotorDirectionLASTSET = new Vector3(pValue.X, pValue.Y, pValue.Z);
                    break;
                case Vehicle.LINEAR_MOTOR_OFFSET:
                    m_linearMotorOffset = new Vector3(pValue.X, pValue.Y, pValue.Z);
                    break;
                case Vehicle.BLOCK_EXIT:
                    m_BlockingEndPoint = new Vector3(pValue.X, pValue.Y, pValue.Z);
                    break;
            }
        }//end ProcessVectorVehicleParam

        internal void ProcessRotationVehicleParam(Vehicle pParam, Quaternion pValue)
        {
            VDetailLog("{0},ProcessRotationalVehicleParam,param={1},val={2}", Prim.LocalID, pParam, pValue);
            switch (pParam)
            {
                case Vehicle.REFERENCE_FRAME:
                    m_referenceFrame = pValue;
                    break;
                case Vehicle.ROLL_FRAME:
                    m_RollreferenceFrame = pValue;
                    break;
            }
        }//end ProcessRotationVehicleParam

        internal void ProcessVehicleFlags(int pParam, bool remove)
        {
            VDetailLog("{0},ProcessVehicleFlags,param={1},remove={2}", Prim.LocalID, pParam, remove);
            VehicleFlag parm = (VehicleFlag)pParam;
            if (pParam == -1)
                m_flags = (VehicleFlag)0;
            else
            {
                if (remove)
                    m_flags &= ~parm;
                else
                    m_flags |= parm;
            }
        }

        internal void ProcessTypeChange(Vehicle pType)
        {
            VDetailLog("{0},ProcessTypeChange,type={1}", Prim.LocalID, pType);
            // Set Defaults For Type
            Type = pType;
            switch (pType)
            {
                case Vehicle.TYPE_NONE:
                    m_linearMotorDirection = Vector3.Zero;
                    m_linearMotorTimescale = 0;
                    m_linearMotorDecayTimescale = 0;
                    m_linearFrictionTimescale = new Vector3(0, 0, 0);

                    m_angularMotorDirection = Vector3.Zero;
                    m_angularMotorDecayTimescale = 0;
                    m_angularMotorTimescale = 0;
                    m_angularFrictionTimescale = new Vector3(0, 0, 0);

                    m_VhoverHeight = 0;
                    m_VhoverEfficiency = 0;
                    m_VhoverTimescale = 0;
                    m_VehicleBuoyancy = 0;
                    
                    m_linearDeflectionEfficiency = 1;
                    m_linearDeflectionTimescale = 1;

                    m_angularDeflectionEfficiency = 0;
                    m_angularDeflectionTimescale = 1000;

                    m_verticalAttractionEfficiency = 0;
                    m_verticalAttractionTimescale = 0;

                    m_bankingEfficiency = 0;
                    m_bankingTimescale = 1000;
                    m_bankingMix = 1;

                    m_referenceFrame = Quaternion.Identity;
                    m_flags = (VehicleFlag)0;
                    break;

                case Vehicle.TYPE_SLED:
                    m_linearMotorDirection = Vector3.Zero;
                    m_linearMotorTimescale = 1000;
                    m_linearMotorDecayTimescale = 120;
                    m_linearFrictionTimescale = new Vector3(30, 1, 1000);

                    m_angularMotorDirection = Vector3.Zero;
                    m_angularMotorTimescale = 1000;
                    m_angularMotorDecayTimescale = 120;
                    m_angularFrictionTimescale = new Vector3(1000, 1000, 1000);

                    m_VhoverHeight = 0;
                    m_VhoverEfficiency = 10;    // TODO: this looks wrong!!
                    m_VhoverTimescale = 10;
                    m_VehicleBuoyancy = 0;

                    m_linearDeflectionEfficiency = 1;
                    m_linearDeflectionTimescale = 1;

                    m_angularDeflectionEfficiency = 1;
                    m_angularDeflectionTimescale = 1000;

                    m_verticalAttractionEfficiency = 0;
                    m_verticalAttractionTimescale = 0;

                    m_bankingEfficiency = 0;
                    m_bankingTimescale = 10;
                    m_bankingMix = 1;

                    m_referenceFrame = Quaternion.Identity;
                    m_flags |= (VehicleFlag.NO_DEFLECTION_UP | VehicleFlag.LIMIT_ROLL_ONLY | VehicleFlag.LIMIT_MOTOR_UP);
                    m_flags &=
                         ~(VehicleFlag.HOVER_WATER_ONLY | VehicleFlag.HOVER_TERRAIN_ONLY |
                           VehicleFlag.HOVER_GLOBAL_HEIGHT | VehicleFlag.HOVER_UP_ONLY);
                    break;
                case Vehicle.TYPE_CAR:
                    m_linearMotorDirection = Vector3.Zero;
                    m_linearMotorTimescale = 1;
                    m_linearMotorDecayTimescale = 60;
                    m_linearFrictionTimescale = new Vector3(100, 2, 1000);

                    m_angularMotorDirection = Vector3.Zero;
                    m_angularMotorTimescale = 1;
                    m_angularMotorDecayTimescale = 0.8f;
                    m_angularFrictionTimescale = new Vector3(1000, 1000, 1000);

                    m_VhoverHeight = 0;
                    m_VhoverEfficiency = 0;
                    m_VhoverTimescale = 1000;
                    m_VehicleBuoyancy = 0;

                    m_linearDeflectionEfficiency = 1;
                    m_linearDeflectionTimescale = 2;

                    m_angularDeflectionEfficiency = 0;
                    m_angularDeflectionTimescale = 10;

                    m_verticalAttractionEfficiency = 1f;
                    m_verticalAttractionTimescale = 10f;

                    m_bankingEfficiency = -0.2f;
                    m_bankingMix = 1;
                    m_bankingTimescale = 1;

                    m_referenceFrame = Quaternion.Identity;
                    m_flags &= ~(VehicleFlag.HOVER_WATER_ONLY
                                | VehicleFlag.HOVER_TERRAIN_ONLY
                                | VehicleFlag.HOVER_GLOBAL_HEIGHT);
                    m_flags |= (VehicleFlag.NO_DEFLECTION_UP
                                | VehicleFlag.LIMIT_ROLL_ONLY
                                | VehicleFlag.LIMIT_MOTOR_UP
                                | VehicleFlag.HOVER_UP_ONLY);
                    break;
                case Vehicle.TYPE_BOAT:
                    m_linearMotorDirection = Vector3.Zero;
                    m_linearMotorTimescale = 5;
                    m_linearMotorDecayTimescale = 60;
                    m_linearFrictionTimescale = new Vector3(10, 3, 2);

                    m_angularMotorDirection = Vector3.Zero;
                    m_angularMotorTimescale = 4;
                    m_angularMotorDecayTimescale = 4;
                    m_angularFrictionTimescale = new Vector3(10,10,10);

                    m_VhoverHeight = 0;
                    m_VhoverEfficiency = 0.5f;
                    m_VhoverTimescale = 2;
                    m_VehicleBuoyancy = 1;

                    m_linearDeflectionEfficiency = 0.5f;
                    m_linearDeflectionTimescale = 3;

                    m_angularDeflectionEfficiency = 0.5f;
                    m_angularDeflectionTimescale = 5;

                    m_verticalAttractionEfficiency = 0.5f;
                    m_verticalAttractionTimescale = 5f;

                    m_bankingEfficiency = -0.3f;
                    m_bankingMix = 0.8f;
                    m_bankingTimescale = 1;

                    m_referenceFrame = Quaternion.Identity;
                    m_flags &= ~(VehicleFlag.HOVER_TERRAIN_ONLY
                                    | VehicleFlag.HOVER_GLOBAL_HEIGHT
                                    | VehicleFlag.LIMIT_ROLL_ONLY
                                    | VehicleFlag.HOVER_UP_ONLY);
                    m_flags |= (VehicleFlag.NO_DEFLECTION_UP
                                    | VehicleFlag.LIMIT_MOTOR_UP
                                    | VehicleFlag.HOVER_WATER_ONLY);
                    break;
                case Vehicle.TYPE_AIRPLANE:
                    m_linearMotorDirection = Vector3.Zero;
                    m_linearMotorTimescale = 2;
                    m_linearMotorDecayTimescale = 60;
                    m_linearFrictionTimescale = new Vector3(200, 10, 5);

                    m_angularMotorDirection = Vector3.Zero;
                    m_angularMotorTimescale = 4;
                    m_angularMotorDecayTimescale = 4;
                    m_angularFrictionTimescale = new Vector3(20, 20, 20);

                    m_VhoverHeight = 0;
                    m_VhoverEfficiency = 0.5f;
                    m_VhoverTimescale = 1000;
                    m_VehicleBuoyancy = 0;

                    m_linearDeflectionEfficiency = 0.5f;
                    m_linearDeflectionTimescale = 3;

                    m_angularDeflectionEfficiency = 1;
                    m_angularDeflectionTimescale = 2;

                    m_verticalAttractionEfficiency = 0.9f;
                    m_verticalAttractionTimescale = 2f;

                    m_bankingEfficiency = 1;
                    m_bankingMix = 0.7f;
                    m_bankingTimescale = 2;

                    m_referenceFrame = Quaternion.Identity;
                    m_flags &= ~(VehicleFlag.HOVER_WATER_ONLY
                                    | VehicleFlag.HOVER_TERRAIN_ONLY
                                    | VehicleFlag.HOVER_GLOBAL_HEIGHT
                                    | VehicleFlag.HOVER_UP_ONLY
                                    | VehicleFlag.NO_DEFLECTION_UP
                                    | VehicleFlag.LIMIT_MOTOR_UP);
                    m_flags |= (VehicleFlag.LIMIT_ROLL_ONLY);
                    break;
                case Vehicle.TYPE_BALLOON:
                    m_linearMotorDirection = Vector3.Zero;
                    m_linearMotorTimescale = 5;
                    m_linearFrictionTimescale = new Vector3(5, 5, 5);
                    m_linearMotorDecayTimescale = 60;

                    m_angularMotorDirection = Vector3.Zero;
                    m_angularMotorTimescale = 6;
                    m_angularFrictionTimescale = new Vector3(10, 10, 10);
                    m_angularMotorDecayTimescale = 10;

                    m_VhoverHeight = 5;
                    m_VhoverEfficiency = 0.8f;
                    m_VhoverTimescale = 10;
                    m_VehicleBuoyancy = 1;

                    m_linearDeflectionEfficiency = 0;
                    m_linearDeflectionTimescale = 5;

                    m_angularDeflectionEfficiency = 0;
                    m_angularDeflectionTimescale = 5;

                    m_verticalAttractionEfficiency = 1f;
                    m_verticalAttractionTimescale = 100f;

                    m_bankingEfficiency = 0;
                    m_bankingMix = 0.7f;
                    m_bankingTimescale = 5;
                    m_referenceFrame = Quaternion.Identity;

                    m_referenceFrame = Quaternion.Identity;
                    m_flags &= ~(VehicleFlag.HOVER_WATER_ONLY
                                    | VehicleFlag.HOVER_TERRAIN_ONLY
                                    | VehicleFlag.HOVER_UP_ONLY
                                    | VehicleFlag.NO_DEFLECTION_UP
                                    | VehicleFlag.LIMIT_MOTOR_UP);
                    m_flags |= (VehicleFlag.LIMIT_ROLL_ONLY
                                    | VehicleFlag.HOVER_GLOBAL_HEIGHT);
                    break;
            }
        }

        // Some of the properties of this prim may have changed.
        // Do any updating needed for a vehicle
        public void Refresh()
        {
            if (IsActive)
            {
                // Friction effects are handled by this vehicle code
                BulletSimAPI.SetFriction2(Prim.PhysBody.ptr, 0f);
                BulletSimAPI.SetHitFraction2(Prim.PhysBody.ptr, 0f);
            }
        }

        // One step of the vehicle properties for the next 'pTimestep' seconds.
        internal void Step(float pTimestep)
        {
            if (!IsActive) return;

            // DEBUG
            // Because Bullet does apply forces to the vehicle, our last computed
            //     linear and angular velocities are not what is happening now.
            // Vector3 externalAngularVelocity = Prim.ForceRotationalVelocity - m_lastAngularVelocity;
            // m_lastAngularVelocity += (externalAngularVelocity * 0.5f) * pTimestep;
            // m_lastAngularVelocity = Prim.ForceRotationalVelocity;   // DEBUG: account for what Bullet did last time
            // m_lastLinearVelocityVector = Prim.ForceVelocity * Quaternion.Inverse(Prim.ForceOrientation);        // DEBUG:
            // END DEBUG

            MoveLinear(pTimestep);
            MoveAngular(pTimestep);
            LimitRotation(pTimestep);

            // DEBUG: Trying to figure out why Bullet goes crazy when the root prim is moved.
            // BulletSimAPI.SetInterpolationVelocity2(Prim.BSBody.ptr, m_newVelocity, m_lastAngularVelocity); // DEBUG DEBUG DEBUG

            // remember the position so next step we can limit absolute movement effects
            m_lastPositionVector = Prim.ForcePosition;

            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

        // Apply the effect of the linear motor.
        // Also does hover and float.
        private void MoveLinear(float pTimestep)
        {
            // m_linearMotorDirection is the target direction we are moving relative to the vehicle coordinates
            // m_lastLinearVelocityVector is the current speed we are moving in that direction
            if (m_linearMotorDirection.LengthSquared() > 0.001f)
            {
                Vector3 origDir = m_linearMotorDirection;
                Vector3 origVel = m_lastLinearVelocityVector;
                Vector3 vehicleVelocity = Prim.ForceVelocity * Quaternion.Inverse(Prim.ForceOrientation);   // DEBUG

                // add drive to body
                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}",
                                Prim.LocalID, origDir, origVel, vehicleVelocity, addAmount, decayFactor, frictionFactor, 
                                m_linearMotorDirection, m_lastLinearVelocityVector, m_newVelocity);
            }
            else
            {
                // if what remains of direction is very small, zero it.
                m_linearMotorDirection = Vector3.Zero;
                m_lastLinearVelocityVector = Vector3.Zero;
                m_newVelocity = Vector3.Zero;

                VDetailLog("{0},MoveLinear,zeroed", Prim.LocalID);
            }

            // m_newVelocity is velocity computed from linear motor in world coordinates

            // Gravity and Buoyancy
            // There is some gravity, make a gravity force vector that is applied after object velocity.
            // m_VehicleBuoyancy: -1=2g; 0=1g; 1=0g;
            Vector3 grav = Prim.PhysicsScene.DefaultGravity * (1f - m_VehicleBuoyancy);

            /*
             * RA: Not sure why one would do this unless we are hoping external forces are doing gravity, ...
            // Preserve the current Z velocity
            Vector3 vel_now = m_prim.Velocity;
            m_dir.Z = vel_now.Z;        // Preserve the accumulated falling velocity
             */

            Vector3 pos = Prim.ForcePosition;
//            Vector3 accel = new Vector3(-(m_dir.X - m_lastLinearVelocityVector.X / 0.1f), -(m_dir.Y - m_lastLinearVelocityVector.Y / 0.1f), m_dir.Z - m_lastLinearVelocityVector.Z / 0.1f);

            // 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.
            // Vector3 rotatedSize = m_prim.Size * m_prim.ForceOrientation;
            // if (rotatedSize.Z < terrainHeight)
            if (pos.Z < terrainHeight)
            {
                pos.Z = terrainHeight + 2;
                Prim.ForcePosition = pos;
                VDetailLog("{0},MoveLinear,terrainHeight,terrainHeight={1},pos={2}", Prim.LocalID, terrainHeight, pos);
            }

            // Check if hovering
            // m_VhoverEfficiency: 0=bouncy, 1=totally damped
            // m_VhoverTimescale: time to achieve height
            if ((m_flags & (VehicleFlag.HOVER_WATER_ONLY | VehicleFlag.HOVER_TERRAIN_ONLY | VehicleFlag.HOVER_GLOBAL_HEIGHT)) != 0)
            {
                // We should hover, get the target height
                if ((m_flags & VehicleFlag.HOVER_WATER_ONLY) != 0)
                {
                    m_VhoverTargetHeight = Prim.PhysicsScene.GetWaterLevelAtXYZ(pos) + m_VhoverHeight;
                }
                if ((m_flags & VehicleFlag.HOVER_TERRAIN_ONLY) != 0)
                {
                    m_VhoverTargetHeight = terrainHeight + m_VhoverHeight;
                }
                if ((m_flags & VehicleFlag.HOVER_GLOBAL_HEIGHT) != 0)
                {
                    m_VhoverTargetHeight = m_VhoverHeight;
                }

                if ((m_flags & VehicleFlag.HOVER_UP_ONLY) != 0)
                {
                    // If body is aready heigher, use its height as target height
                    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)
                    {
                        Prim.ForcePosition = pos;
                    }
                }
                else
                {
                    float verticalError = pos.Z - m_VhoverTargetHeight;
                    // RA: where does the 50 come from?
                    float verticalCorrectionVelocity = pTimestep * ((verticalError * 50.0f) / m_VhoverTimescale);
                    // Replace Vertical speed with correction figure if significant
                    if (Math.Abs(verticalError) > 0.01f)
                    {
                        m_newVelocity.Z += verticalCorrectionVelocity;
                        //KF: m_VhoverEfficiency is not yet implemented
                    }
                    else if (verticalError < -0.01)
                    {
                        m_newVelocity.Z -= verticalCorrectionVelocity;
                    }
                    else
                    {
                        m_newVelocity.Z = 0f;
                    }
                }

                VDetailLog("{0},MoveLinear,hover,pos={1},dir={2},height={3},target={4}", Prim.LocalID, pos, m_newVelocity, m_VhoverHeight, m_VhoverTargetHeight);
            }

            Vector3 posChange = pos - m_lastPositionVector;
            if (m_BlockingEndPoint != Vector3.Zero)
            {
                bool changed = false;
                if (pos.X >= (m_BlockingEndPoint.X - (float)1))
                {
                    pos.X -= posChange.X + 1;
                    changed = true;
                }
                if (pos.Y >= (m_BlockingEndPoint.Y - (float)1))
                {
                    pos.Y -= posChange.Y + 1;
                    changed = true;
                }
                if (pos.Z >= (m_BlockingEndPoint.Z - (float)1))
                {
                    pos.Z -= posChange.Z + 1;
                    changed = true;
                }
                if (pos.X <= 0)
                {
                    pos.X += posChange.X + 1;
                    changed = true;
                }
                if (pos.Y <= 0)
                {
                    pos.Y += posChange.Y + 1;
                    changed = true;
                }
                if (changed)
                {
                    Prim.ForcePosition = pos;
                    VDetailLog("{0},MoveLinear,blockingEndPoint,block={1},origPos={2},pos={3}",
                                Prim.LocalID, m_BlockingEndPoint, posChange, pos);
                }
            }

            // Limit absolute vertical change
            float Zchange = Math.Abs(posChange.Z);
            if ((m_flags & (VehicleFlag.LIMIT_MOTOR_UP)) != 0)
            {
                if (Zchange > .3)
                    grav.Z = (float)(grav.Z * 3);
                if (Zchange > .15)
                    grav.Z = (float)(grav.Z * 2);
                if (Zchange > .75)
                    grav.Z = (float)(grav.Z * 1.5);
                if (Zchange > .05)
                    grav.Z = (float)(grav.Z * 1.25);
                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);
            }

            // If not changing some axis, reduce out velocity
            if ((m_flags & (VehicleFlag.NO_X)) != 0)
                m_newVelocity.X = 0;
            if ((m_flags & (VehicleFlag.NO_Y)) != 0)
                m_newVelocity.Y = 0;
            if ((m_flags & (VehicleFlag.NO_Z)) != 0)
                m_newVelocity.Z = 0;

            // Apply velocity
            Prim.ForceVelocity = m_newVelocity;
            // Prim.AddForce(m_newVelocity * Prim.Linkset.LinksetMass, false);
            Prim.AddForce(grav * Prim.Linkset.LinksetMass, false);

            VDetailLog("{0},MoveLinear,done,lmDir={1},lmVel={2},newVel={3},grav={4}",
                    Prim.LocalID, m_linearMotorDirection, m_lastLinearVelocityVector, m_newVelocity, grav);

        } // end MoveLinear()

        // =======================================================================
        // Apply the effect of the angular motor.
        private void MoveAngular(float pTimestep)
        {
            // m_angularMotorDirection         // angular velocity requested by LSL motor
            // m_angularMotorApply             // application frame counter
            // m_angularMotorVelocity          // current angular motor velocity (ramps up and down)
            // m_angularMotorTimescale         // motor angular velocity ramp up rate
            // m_angularMotorDecayTimescale    // motor angular velocity decay rate
            // m_angularFrictionTimescale      // body angular velocity  decay rate
            // m_lastAngularVelocity           // what was last applied to body

            if (m_angularMotorDirection.LengthSquared() > 0.0001)
            {
                Vector3 origVel = m_angularMotorVelocity;
                Vector3 origDir = m_angularMotorDirection;

                //       new velocity    +=                      error                       /  (  time to get there   / step interval)
                //                             requested speed     -    last motor speed
                m_angularMotorVelocity += (m_angularMotorDirection - m_angularMotorVelocity) /  (m_angularMotorTimescale / pTimestep);
                // decay requested direction
                m_angularMotorDirection *= (1.0f - (pTimestep * 1.0f/m_angularMotorDecayTimescale));

                VDetailLog("{0},MoveAngular,angularMotorApply,angTScale={1},timeStep={2},origvel={3},origDir={4},vel={5}",
                        Prim.LocalID, m_angularMotorTimescale, pTimestep, origVel, origDir, m_angularMotorVelocity);
            }
            else
            {
                m_angularMotorVelocity = Vector3.Zero;
            }

            #region Vertical attactor

            Vector3 vertattr = Vector3.Zero;
            Vector3 deflection = Vector3.Zero;
            Vector3 banking = Vector3.Zero;

            if (m_verticalAttractionTimescale < 300 && m_lastAngularVelocity != Vector3.Zero)
            {
                float VAservo = pTimestep * 0.2f / m_verticalAttractionTimescale;
                if (Prim.Linkset.LinksetIsColliding)
                    VAservo = pTimestep * 0.05f / (m_verticalAttractionTimescale);

                VAservo *= (m_verticalAttractionEfficiency * m_verticalAttractionEfficiency);

                // Create a vector of the vehicle "up" in world coordinates
                Vector3 verticalError = Vector3.UnitZ * Prim.ForceOrientation;
                // verticalError.X and .Y are the World error amounts. They are 0 when there is no
                //      error (Vehicle Body is 'vertical'), and .Z will be 1. As the body leans to its
                //      side |.X| will increase to 1 and .Z fall to 0. As body inverts |.X| will fall
                //      and .Z will go // negative. Similar for tilt and |.Y|. .X and .Y must be
                //      modulated to prevent a stable inverted body.

                // Error is 0 (no error) to +/- 2 (max error)
                if (verticalError.Z < 0.0f)
                {
                    verticalError.X = 2.0f - verticalError.X;
                    verticalError.Y = 2.0f - verticalError.Y;
                }
                // scale it by VAservo
                verticalError = verticalError * VAservo;

                // As the body rotates around the X axis, then verticalError.Y increases; Rotated around Y
                //     then .X increases, so change  Body angular velocity  X based on Y, and Y based on X.
                //     Z is not changed.
                vertattr.X =    verticalError.Y;
                vertattr.Y =  - verticalError.X;
                vertattr.Z = 0f;

                // scaling appears better usingsquare-law
                Vector3 angularVelocity = Prim.ForceRotationalVelocity;
                float bounce = 1.0f - (m_verticalAttractionEfficiency * m_verticalAttractionEfficiency);
                vertattr.X += bounce * angularVelocity.X;
                vertattr.Y += bounce * angularVelocity.Y;

                VDetailLog("{0},MoveAngular,verticalAttraction,verticalError={1},bounce={2},vertattr={3}",
                            Prim.LocalID, 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 =
                    new Vector3((pTimestep * 10 * (m_angularDeflectionEfficiency / m_angularDeflectionTimescale)), 0, 0);
                preferredAxisOfMotion *= Quaternion.Add(Prim.ForceOrientation, m_referenceFrame);

                deflection = (preferredAxisOfMotion * (m_angularDeflectionEfficiency) / m_angularDeflectionTimescale) * pTimestep;

                VDetailLog("{0},MoveAngular,Deflection,perfAxis={1},deflection={2}", 
                                        Prim.LocalID, preferredAxisOfMotion, deflection);
            }

            #endregion

            #region Banking

            if (m_bankingEfficiency != 0)
            {
                Vector3 dir = Vector3.One * Prim.ForceOrientation;
                float mult = (m_bankingMix*m_bankingMix)*-1*(m_bankingMix < 0 ? -1 : 1);
                    //Changes which way it banks in and out of turns

                //Use the square of the efficiency, as it looks much more how SL banking works
                float effSquared = (m_bankingEfficiency*m_bankingEfficiency);
                if (m_bankingEfficiency < 0)
                    effSquared *= -1; //Keep the negative!

                float mix = Math.Abs(m_bankingMix);
                if (m_angularMotorVelocity.X == 0)
                {
                    /*if (!parent.Orientation.ApproxEquals(this.m_referenceFrame, 0.25f))
                    {
                        Vector3 axisAngle;
                        float angle;
                        parent.Orientation.GetAxisAngle(out axisAngle, out angle);
                        Vector3 rotatedVel = parent.Velocity * parent.Orientation;
                        if ((rotatedVel.X < 0 && axisAngle.Y > 0) || (rotatedVel.X > 0 && axisAngle.Y < 0))
                            m_angularMotorVelocity.X += (effSquared * (mult * mix)) * (1f) * 10;
                        else
                            m_angularMotorVelocity.X += (effSquared * (mult * mix)) * (-1f) * 10;
                    }*/
                }
                else
                    banking.Z += (effSquared*(mult*mix))*(m_angularMotorVelocity.X) * 4;
                if (!Prim.Linkset.LinksetIsColliding && 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;
                    /*if(angVelZ > mix)
                        angVelZ = mix;
                    else if(angVelZ < -mix)
                        angVelZ = -mix;*/
                    //This controls how fast and how far the banking occurs
                    Vector3 bankingRot = new Vector3(angVelZ*(effSquared*mult), 0, 0);
                    if (bankingRot.X > 3)
                        bankingRot.X = 3;
                    else if (bankingRot.X < -3)
                        bankingRot.X = -3;
                    bankingRot *= Prim.ForceOrientation;
                    banking += bankingRot;
                }
                m_angularMotorVelocity.X *= m_bankingEfficiency == 1 ? 0.0f : 1 - m_bankingEfficiency;
                VDetailLog("{0},MoveAngular,Banking,bEff={1},angMotVel={2},banking={3}", 
                                Prim.LocalID, m_bankingEfficiency, m_angularMotorVelocity, banking);
            }

            #endregion

            m_lastVertAttractor = vertattr;

            // Sum velocities
            m_lastAngularVelocity = m_angularMotorVelocity + vertattr + banking + deflection;

            if ((m_flags & (VehicleFlag.NO_DEFLECTION_UP)) != 0)
            {
                m_lastAngularVelocity.X = 0;
                m_lastAngularVelocity.Y = 0;
                VDetailLog("{0},MoveAngular,noDeflectionUp,lastAngular={1}", Prim.LocalID, m_lastAngularVelocity);
            }

            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);
            }

            // Apply to the body
            // 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}", 
                                Prim.LocalID, applyAngularForce, decayamount, m_lastAngularVelocity);
        } //end MoveAngular

        internal void LimitRotation(float timestep)
        {
            Quaternion rotq = Prim.ForceOrientation;
            Quaternion m_rot = rotq;
            if (m_RollreferenceFrame != Quaternion.Identity)
            {
                if (rotq.X >= m_RollreferenceFrame.X)
                {
                    m_rot.X = rotq.X - (m_RollreferenceFrame.X / 2);
                }
                if (rotq.Y >= m_RollreferenceFrame.Y)
                {
                    m_rot.Y = rotq.Y - (m_RollreferenceFrame.Y / 2);
                }
                if (rotq.X <= -m_RollreferenceFrame.X)
                {
                    m_rot.X = rotq.X + (m_RollreferenceFrame.X / 2);
                }
                if (rotq.Y <= -m_RollreferenceFrame.Y)
                {
                    m_rot.Y = rotq.Y + (m_RollreferenceFrame.Y / 2);
                }
            }
            if ((m_flags & VehicleFlag.LOCK_ROTATION) != 0)
            {
                m_rot.X = 0;
                m_rot.Y = 0;
            }
            if (rotq != m_rot)
            {
                Prim.ForceOrientation = m_rot;
                VDetailLog("{0},LimitRotation,done,orig={1},new={2}", Prim.LocalID, rotq, m_rot);
            }

        }

        // Invoke the detailed logger and output something if it's enabled.
        private void VDetailLog(string msg, params Object[] args)
        {
            if (Prim.PhysicsScene.VehicleLoggingEnabled)
                Prim.PhysicsScene.DetailLog(msg, args);
        }
    }
}