* Initial commit of BulletSimN (BulletSNPlugin). Purely C# implementation of BulletSim. This is designed to be /as close as possible/ to the BulletSim plugin while still being entirely in the managed space to make keeping it up to date easy as possible (no thinking work). This implementation is /slower/ then the c++ version just because it's fully managed, so it's not appropriate for huge sims, but it will run small ones OK. At the moment, it supports all known features of BulletSim. Think of it like.. POS but everything works. To use this plugin, set the physics plugin to BulletSimN.

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diff --git a/OpenSim/Region/Physics/BulletSNPlugin/BSPhysObject.cs b/OpenSim/Region/Physics/BulletSNPlugin/BSPhysObject.cs
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+/*
+ * 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 copyrightD
+ *       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.
+ */
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+using OMV = OpenMetaverse;
+using OpenSim.Framework;
+using OpenSim.Region.Physics.Manager;
+
+namespace OpenSim.Region.Physics.BulletSNPlugin
+{
+/*
+ * Class to wrap all objects.
+ * The rest of BulletSim doesn't need to keep checking for avatars or prims
+ *        unless the difference is significant.
+ * 
+ *  Variables in the physicsl objects are in three forms:
+ *      VariableName: used by the simulator and performs taint operations, etc
+ *      RawVariableName: direct reference to the BulletSim storage for the variable value
+ *      ForceVariableName: direct reference (store and fetch) to the value in the physics engine.
+ *  The last two (and certainly the last one) should be referenced only in taint-time.
+ */
+
+/*
+ * As of 20121221, the following are the call sequences (going down) for different script physical functions:
+ * llApplyImpulse       llApplyRotImpulse           llSetTorque             llSetForce
+ * SOP.ApplyImpulse     SOP.ApplyAngularImpulse     SOP.SetAngularImpulse   SOP.SetForce
+ * SOG.ApplyImpulse     SOG.ApplyAngularImpulse     SOG.SetAngularImpulse
+ * PA.AddForce          PA.AddAngularForce          PA.Torque = v           PA.Force = v
+ * BS.ApplyCentralForce BS.ApplyTorque              
+ */
+
+public abstract class BSPhysObject : PhysicsActor
+{
+    protected BSPhysObject()
+    {
+    }
+    protected BSPhysObject(BSScene parentScene, uint localID, string name, string typeName)
+    {
+        PhysicsScene = parentScene;
+        LocalID = localID;
+        PhysObjectName = name;
+        TypeName = typeName;
+
+        Linkset = BSLinkset.Factory(PhysicsScene, this);
+        LastAssetBuildFailed = false;
+
+        // Default material type
+        Material = MaterialAttributes.Material.Wood;
+
+        CollisionCollection = new CollisionEventUpdate();
+        SubscribedEventsMs = 0;
+        CollidingStep = 0;
+        CollidingGroundStep = 0;
+    }
+
+    // Tell the object to clean up.
+    public virtual void Destroy()
+    {
+        UnRegisterAllPreStepActions();
+    }
+
+    public BSScene PhysicsScene { get; protected set; }
+    // public override uint LocalID { get; set; } // Use the LocalID definition in PhysicsActor
+    public string PhysObjectName { get; protected set; }
+    public string TypeName { get; protected set; }
+
+    public BSLinkset Linkset { get; set; }
+    public BSLinksetInfo LinksetInfo { get; set; }
+
+    // Return the object mass without calculating it or having side effects
+    public abstract float RawMass { get; }
+    // Set the raw mass but also update physical mass properties (inertia, ...)
+    public abstract void UpdatePhysicalMassProperties(float mass);
+
+    // The last value calculated for the prim's inertia
+    public OMV.Vector3 Inertia { get; set; }
+
+    // Reference to the physical body (btCollisionObject) of this object
+    public BulletBody PhysBody;
+    // Reference to the physical shape (btCollisionShape) of this object
+    public BulletShape PhysShape;
+
+    // 'true' if the mesh's underlying asset failed to build.
+    // This will keep us from looping after the first time the build failed.
+    public bool LastAssetBuildFailed { get; set; }
+
+    // The objects base shape information. Null if not a prim type shape.
+    public PrimitiveBaseShape BaseShape { get; protected set; }
+    // Some types of objects have preferred physical representations.
+    // Returns SHAPE_UNKNOWN if there is no preference.
+    public virtual BSPhysicsShapeType PreferredPhysicalShape
+    {
+        get { return BSPhysicsShapeType.SHAPE_UNKNOWN; }
+    }
+
+    // When the physical properties are updated, an EntityProperty holds the update values.
+    // Keep the current and last EntityProperties to enable computation of differences
+    //      between the current update and the previous values.
+    public EntityProperties CurrentEntityProperties { get; set; }
+    public EntityProperties LastEntityProperties { get; set; }
+
+    public virtual OMV.Vector3 Scale { get; set; }
+    public abstract bool IsSolid { get; }
+    public abstract bool IsStatic { get; }
+
+    // Materialness
+    public MaterialAttributes.Material Material { get; private set; }
+    public override void SetMaterial(int material)
+    {
+        Material = (MaterialAttributes.Material)material;
+    }
+
+    // Stop all physical motion.
+    public abstract void ZeroMotion(bool inTaintTime);
+    public abstract void ZeroAngularMotion(bool inTaintTime);
+
+    // Step the vehicle simulation for this object. A NOOP if the vehicle was not configured.
+    public virtual void StepVehicle(float timeStep) { }
+
+    // Update the physical location and motion of the object. Called with data from Bullet.
+    public abstract void UpdateProperties(EntityProperties entprop);
+
+    public abstract OMV.Vector3 RawPosition { get; set; }
+    public abstract OMV.Vector3 ForcePosition { get; set; }
+
+    public abstract OMV.Quaternion RawOrientation { get; set; }
+    public abstract OMV.Quaternion ForceOrientation { get; set; }
+
+    // The system is telling us the velocity it wants to move at.
+    // protected OMV.Vector3 m_targetVelocity;  // use the definition in PhysicsActor
+    public override OMV.Vector3 TargetVelocity
+    {
+        get { return m_targetVelocity; }
+        set
+        {
+            m_targetVelocity = value;
+            Velocity = value;
+        }
+    }
+    public abstract OMV.Vector3 ForceVelocity { get; set; }
+
+    public abstract OMV.Vector3 ForceRotationalVelocity { get; set; }
+
+    public abstract float ForceBuoyancy { get; set; }
+
+    public virtual bool ForceBodyShapeRebuild(bool inTaintTime) { return false; }
+
+    #region Collisions
+
+    // Requested number of milliseconds between collision events. Zero means disabled.
+    protected int SubscribedEventsMs { get; set; }
+    // Given subscription, the time that a collision may be passed up
+    protected int NextCollisionOkTime { get; set; }
+    // The simulation step that last had a collision
+    protected long CollidingStep { get; set; }
+    // The simulation step that last had a collision with the ground
+    protected long CollidingGroundStep { get; set; }
+    // The collision flags we think are set in Bullet
+    protected CollisionFlags CurrentCollisionFlags { get; set; }
+
+    // The collisions that have been collected this tick
+    protected CollisionEventUpdate CollisionCollection;
+
+    // The simulation step is telling this object about a collision.
+    // Return 'true' if a collision was processed and should be sent up.
+    // Called at taint time from within the Step() function
+    public virtual bool Collide(uint collidingWith, BSPhysObject collidee,
+                    OMV.Vector3 contactPoint, OMV.Vector3 contactNormal, float pentrationDepth)
+    {
+        bool ret = false;
+
+        // The following lines make IsColliding() and IsCollidingGround() work
+        CollidingStep = PhysicsScene.SimulationStep;
+        if (collidingWith <= PhysicsScene.TerrainManager.HighestTerrainID)
+        {
+            CollidingGroundStep = PhysicsScene.SimulationStep;
+        }
+
+        // prims in the same linkset cannot collide with each other
+        if (collidee != null && (this.Linkset.LinksetID == collidee.Linkset.LinksetID))
+        {
+            return ret;
+        }
+
+        // if someone has subscribed for collision events....
+        if (SubscribedEvents()) {
+            CollisionCollection.AddCollider(collidingWith, new ContactPoint(contactPoint, contactNormal, pentrationDepth));
+            DetailLog("{0},{1}.Collison.AddCollider,call,with={2},point={3},normal={4},depth={5}",
+                            LocalID, TypeName, collidingWith, contactPoint, contactNormal, pentrationDepth);
+
+            ret = true;
+        }
+        return ret;
+    }
+
+    // Send the collected collisions into the simulator.
+    // Called at taint time from within the Step() function thus no locking problems
+    //      with CollisionCollection and ObjectsWithNoMoreCollisions.
+    // Return 'true' if there were some actual collisions passed up
+    public virtual bool SendCollisions()
+    {
+        bool ret = true;
+        // If the 'no collision' call, force it to happen right now so quick collision_end
+        bool force = (CollisionCollection.Count == 0);
+
+        // throttle the collisions to the number of milliseconds specified in the subscription
+        if (force || (PhysicsScene.SimulationNowTime >= NextCollisionOkTime))
+        {
+            NextCollisionOkTime = PhysicsScene.SimulationNowTime + SubscribedEventsMs;
+
+            // We are called if we previously had collisions. If there are no collisions
+            //   this time, send up one last empty event so OpenSim can sense collision end.
+            if (CollisionCollection.Count == 0)
+            {
+                // If I have no collisions this time, remove me from the list of objects with collisions.
+                ret = false;
+            }
+
+            // DetailLog("{0},{1}.SendCollisionUpdate,call,numCollisions={2}", LocalID, TypeName, CollisionCollection.Count);
+            base.SendCollisionUpdate(CollisionCollection);
+
+            // The CollisionCollection instance is passed around in the simulator.
+            // Make sure we don't have a handle to that one and that a new one is used for next time.
+            //    This fixes an interesting 'gotcha'. If we call CollisionCollection.Clear() here, 
+            //    a race condition is created for the other users of this instance.
+            CollisionCollection = new CollisionEventUpdate();
+        }
+        return ret;
+    }
+
+    // Subscribe for collision events.
+    // Parameter is the millisecond rate the caller wishes collision events to occur.
+    public override void SubscribeEvents(int ms) {
+        // DetailLog("{0},{1}.SubscribeEvents,subscribing,ms={2}", LocalID, TypeName, ms);
+        SubscribedEventsMs = ms;
+        if (ms > 0)
+        {
+            // make sure first collision happens
+            NextCollisionOkTime = Util.EnvironmentTickCountSubtract(SubscribedEventsMs);
+
+            PhysicsScene.TaintedObject(TypeName+".SubscribeEvents", delegate()
+            {
+                if (PhysBody.HasPhysicalBody)
+                    CurrentCollisionFlags = BulletSimAPI.AddToCollisionFlags2(PhysBody.ptr, CollisionFlags.BS_SUBSCRIBE_COLLISION_EVENTS);
+            });
+        }
+        else
+        {
+            // Subscribing for zero or less is the same as unsubscribing
+            UnSubscribeEvents();
+        }
+    }
+    public override void UnSubscribeEvents() {
+        // DetailLog("{0},{1}.UnSubscribeEvents,unsubscribing", LocalID, TypeName);
+        SubscribedEventsMs = 0;
+        PhysicsScene.TaintedObject(TypeName+".UnSubscribeEvents", delegate()
+        {
+            // Make sure there is a body there because sometimes destruction happens in an un-ideal order.
+            if (PhysBody.HasPhysicalBody)
+                CurrentCollisionFlags = BulletSimAPI.RemoveFromCollisionFlags2(PhysBody.ptr, CollisionFlags.BS_SUBSCRIBE_COLLISION_EVENTS);
+        });
+    }
+    // Return 'true' if the simulator wants collision events
+    public override bool SubscribedEvents() {
+        return (SubscribedEventsMs > 0);
+    }
+
+    #endregion // Collisions
+
+    #region Per Simulation Step actions
+    // There are some actions that must be performed for a physical object before each simulation step.
+    // These actions are optional so, rather than scanning all the physical objects and asking them
+    //     if they have anything to do, a physical object registers for an event call before the step is performed.
+    // This bookkeeping makes it easy to add, remove and clean up after all these registrations.
+    private Dictionary<string, BSScene.PreStepAction> RegisteredActions = new Dictionary<string, BSScene.PreStepAction>();
+    protected void RegisterPreStepAction(string op, uint id, BSScene.PreStepAction actn)
+    {
+        string identifier = op + "-" + id.ToString();
+        RegisteredActions[identifier] = actn;
+        PhysicsScene.BeforeStep += actn;
+        DetailLog("{0},BSPhysObject.RegisterPreStepAction,id={1}", LocalID, identifier);
+    }
+
+    // Unregister a pre step action. Safe to call if the action has not been registered.
+    protected void UnRegisterPreStepAction(string op, uint id)
+    {
+        string identifier = op + "-" + id.ToString();
+        bool removed = false;
+        if (RegisteredActions.ContainsKey(identifier))
+        {
+            PhysicsScene.BeforeStep -= RegisteredActions[identifier];
+            RegisteredActions.Remove(identifier);
+            removed = true;
+        }
+        DetailLog("{0},BSPhysObject.UnRegisterPreStepAction,id={1},removed={2}", LocalID, identifier, removed);
+    }
+
+    protected void UnRegisterAllPreStepActions()
+    {
+        foreach (KeyValuePair<string, BSScene.PreStepAction> kvp in RegisteredActions)
+        {
+            PhysicsScene.BeforeStep -= kvp.Value;
+        }
+        RegisteredActions.Clear();
+        DetailLog("{0},BSPhysObject.UnRegisterAllPreStepActions,", LocalID);
+    }
+
+    
+    #endregion // Per Simulation Step actions
+
+    // High performance detailed logging routine used by the physical objects.
+    protected void DetailLog(string msg, params Object[] args)
+    {
+        if (PhysicsScene.PhysicsLogging.Enabled)
+            PhysicsScene.DetailLog(msg, args);
+    }
+
+}
+}