a few more changes on avatar collider

1 files changed, 274 insertions, 73 deletions

diff --git a/OpenSim/Region/Physics/UbitOdePlugin/ODECharacter.cs b/OpenSim/Region/Physics/UbitOdePlugin/ODECharacter.cs
index 15bdc57..1b25faf 100644
--- a/OpenSim/Region/Physics/UbitOdePlugin/ODECharacter.cs
+++ b/OpenSim/Region/Physics/UbitOdePlugin/ODECharacter.cs
@@ -74,7 +74,6 @@ namespace OpenSim.Region.Physics.OdePlugin
 
         private Vector3 _position;
         private Vector3 _zeroPosition;
-        private bool _zeroFlag = false;
         private Vector3 _velocity;
         private Vector3 _target_velocity;
         private Vector3 _acceleration;
@@ -90,11 +89,15 @@ namespace OpenSim.Region.Physics.OdePlugin
         public float PID_D;
         public float PID_P;
 
+        private float timeStep;
+        private float invtimeStep;
+
         private float m_feetOffset = 0;
         private float feetOff = 0;
         private float feetSZ = 0.5f;
         const float feetScale = 0.8f;
         private float boneOff = 0;
+        private float m_lastVelocitySqr = 0;
 
         public float walkDivisor = 1.3f;
         public float runDivisor = 0.8f;
@@ -103,6 +106,9 @@ namespace OpenSim.Region.Physics.OdePlugin
         private bool m_iscollidingGround = false;
         private bool m_iscollidingObj = false;
         private bool m_alwaysRun = false;
+
+        private bool _zeroFlag = false;
+
         private int m_requestedUpdateFrequency = 0;
         private uint m_localID = 0;
         public bool m_returnCollisions = false;
@@ -120,6 +126,7 @@ namespace OpenSim.Region.Physics.OdePlugin
         int m_colliderfilter = 0;
         int m_colliderGroundfilter = 0;
         int m_colliderObjectfilter = 0;
+        bool m_collisionException = false;
 
         // Default we're a Character
         private CollisionCategories m_collisionCategories = (CollisionCategories.Character);
@@ -132,10 +139,11 @@ namespace OpenSim.Region.Physics.OdePlugin
         // we do land collisions not ode                | CollisionCategories.Land);
         public IntPtr Body = IntPtr.Zero;
         private OdeScene _parent_scene;
-        public IntPtr topbox = IntPtr.Zero;
-        public IntPtr midbox = IntPtr.Zero;
-        public IntPtr feetbox = IntPtr.Zero;
-        public IntPtr bonebox = IntPtr.Zero;
+        private IntPtr topbox = IntPtr.Zero;
+        private IntPtr midbox = IntPtr.Zero;
+        private IntPtr feetbox = IntPtr.Zero;
+        private IntPtr bbox = IntPtr.Zero;
+        public IntPtr collider = IntPtr.Zero;
 
         public IntPtr Amotor = IntPtr.Zero;
 
@@ -143,6 +151,7 @@ namespace OpenSim.Region.Physics.OdePlugin
 
 
 
+
         public int m_eventsubscription = 0;
         private int m_cureventsubscription = 0;
         private CollisionEventUpdate CollisionEventsThisFrame = null;
@@ -160,6 +169,9 @@ namespace OpenSim.Region.Physics.OdePlugin
         {
             m_uuid = UUID.Random();
 
+            timeStep = parent_scene.ODE_STEPSIZE;
+            invtimeStep = 1 / timeStep;
+
             if (pos.IsFinite())
             {
                 if (pos.Z > 99999f)
@@ -208,8 +220,8 @@ namespace OpenSim.Region.Physics.OdePlugin
 
             m_mass = m_density * m_size.X * m_size.Y * m_size.Z; ; // sure we have a default           
 
-            PID_D = basePID_D * m_mass / parent_scene.ODE_STEPSIZE;
-            PID_P = basePID_P * m_mass / parent_scene.ODE_STEPSIZE;
+            PID_D = basePID_D * m_mass * invtimeStep;
+            PID_P = basePID_P * m_mass * invtimeStep;
 
             m_isPhysical = false; // current status: no ODE information exists
 
@@ -292,7 +304,7 @@ namespace OpenSim.Region.Physics.OdePlugin
             set
             {
                 flying = value;
-                //                m_log.DebugFormat("[PHYSICS]: Set OdeCharacter Flying to {0}", flying);
+//                m_log.DebugFormat("[PHYSICS]: Set OdeCharacter Flying to {0}", flying);
             }
         }
 
@@ -336,25 +348,25 @@ namespace OpenSim.Region.Physics.OdePlugin
             get { return m_iscollidingGround; }
             set
             {
-                /*  we now control this
-                                if (value)
-                                    {
-                                    m_colliderGroundfilter += 2;
-                                    if (m_colliderGroundfilter > 2)
-                                        m_colliderGroundfilter = 2;
-                                    }
-                                else
-                                    {
-                                    m_colliderGroundfilter--;
-                                    if (m_colliderGroundfilter < 0)
-                                        m_colliderGroundfilter = 0;
-                                    }
-
-                                if (m_colliderGroundfilter == 0)
-                                    m_iscollidingGround = false;
-                                else
-                                    m_iscollidingGround = true;
-                 */
+/*  we now control this
+                if (value)
+                    {
+                    m_colliderGroundfilter += 2;
+                    if (m_colliderGroundfilter > 2)
+                        m_colliderGroundfilter = 2;
+                    }
+                else
+                    {
+                    m_colliderGroundfilter--;
+                    if (m_colliderGroundfilter < 0)
+                        m_colliderGroundfilter = 0;
+                    }
+
+                if (m_colliderGroundfilter == 0)
+                    m_iscollidingGround = false;
+                else
+                    m_iscollidingGround = true;
+ */
             }
 
         }
@@ -386,7 +398,7 @@ namespace OpenSim.Region.Physics.OdePlugin
                 else
                     m_iscollidingObj = true;
 
-                //            m_iscollidingObj = value;
+//            m_iscollidingObj = value;
 
                 if (m_iscollidingObj)
                     m_pidControllerActive = false;
@@ -634,8 +646,8 @@ namespace OpenSim.Region.Physics.OdePlugin
             get { return m_orientation; }
             set
             {
-                //                fakeori = value;
-                //                givefakeori++;
+//                fakeori = value;
+//                givefakeori++;
 
                 value.Normalize();
                 AddChange(changes.Orientation, value);
@@ -690,6 +702,46 @@ namespace OpenSim.Region.Physics.OdePlugin
                 AddChange(changes.Momentum, momentum);
         }
 
+        private void ajustCollider()
+        {
+            float vq = _velocity.LengthSquared();
+            if (m_lastVelocitySqr != vq)
+            {
+                m_lastVelocitySqr = vq;
+                if (vq > 100.0f)
+                {
+                    Vector3 off = _velocity;
+                    float t = 0.5f * timeStep;
+                    off = off * t;
+                    d.GeomSetOffsetPosition(bbox, off.X, off.Y, off.Z);
+                    off.X = 2.0f * (m_size.X + Math.Abs(off.X));
+                    off.Y = 2.0f * (m_size.Y + Math.Abs(off.Y));
+                    off.Z = m_size.Z + 2.0f * Math.Abs(off.Z);
+                    d.GeomBoxSetLengths(bbox, off.X, off.Y, off.Z);
+
+                    d.GeomSetCategoryBits(bbox, (uint)m_collisionCategories);
+                    d.GeomSetCollideBits(bbox, (uint)m_collisionFlags);
+                    d.GeomSetCategoryBits(topbox, 0);
+                    d.GeomSetCollideBits(topbox, 0);
+                    d.GeomSetCategoryBits(midbox, 0);
+                    d.GeomSetCollideBits(midbox, 0);
+                    d.GeomSetCategoryBits(feetbox, 0);
+                    d.GeomSetCollideBits(feetbox, 0);
+                }
+                else
+                {
+                    d.GeomSetCategoryBits(bbox, 0);
+                    d.GeomSetCollideBits(bbox, 0);
+                    d.GeomSetCategoryBits(topbox, (uint)m_collisionCategories);
+                    d.GeomSetCollideBits(topbox, (uint)m_collisionFlags);
+                    d.GeomSetCategoryBits(midbox, (uint)m_collisionCategories);
+                    d.GeomSetCollideBits(midbox, (uint)m_collisionFlags);
+                    d.GeomSetCategoryBits(feetbox, (uint)m_collisionCategories);
+                    d.GeomSetCollideBits(feetbox, (uint)m_collisionFlags);
+                }
+            }
+        }
+
         private void AvatarGeomAndBodyCreation(float npositionX, float npositionY, float npositionZ)
         {
             // sizes  one day should came from visual parameters
@@ -697,7 +749,6 @@ namespace OpenSim.Region.Physics.OdePlugin
             float sy = m_size.Y;
             float sz = m_size.Z;
 
-
             float topsx = sx * 0.9f;
             float midsx = sx;
             float feetsx = sx * feetScale;
@@ -732,21 +783,17 @@ namespace OpenSim.Region.Physics.OdePlugin
 
             _parent_scene.waitForSpaceUnlock(_parent_scene.CharsSpace);
 
-            feetbox = d.CreateBox(_parent_scene.CharsSpace, feetsx, feetsy, feetsz);
-            d.GeomSetCategoryBits(feetbox, (uint)m_collisionCategories);
-            d.GeomSetCollideBits(feetbox, (uint)m_collisionFlags);
-
-            midbox = d.CreateBox(_parent_scene.CharsSpace, midsx, midsy, midsz);
-            d.GeomSetCategoryBits(midbox, (uint)m_collisionCategories);
-            d.GeomSetCollideBits(midbox, (uint)m_collisionFlags);
+            collider = d.HashSpaceCreate(_parent_scene.CharsSpace);
+            d.HashSpaceSetLevels(collider, -4, 3);
+            d.SpaceSetSublevel(collider, 3);
+            d.SpaceSetCleanup(collider, false);
+            d.GeomSetCategoryBits(collider, (uint)m_collisionCategories);
+            d.GeomSetCollideBits(collider, (uint)m_collisionFlags);
 
-            topbox = d.CreateBox(_parent_scene.CharsSpace, topsx, topsy, topsz);
-            d.GeomSetCategoryBits(topbox, (uint)m_collisionCategories);
-            d.GeomSetCollideBits(topbox, (uint)m_collisionFlags);
-
-            bonebox = d.CreateBox(_parent_scene.CharsSpace, bonesx, bonesy, bonesz);
-            d.GeomSetCategoryBits(bonebox, (uint)m_collisionCategories);
-            d.GeomSetCollideBits(bonebox, (uint)m_collisionFlags);
+            feetbox = d.CreateBox(collider, feetsx, feetsy, feetsz);
+            midbox = d.CreateBox(collider, midsx, midsy, midsz);
+            topbox = d.CreateBox(collider, topsx, topsy, topsz);
+            bbox = d.CreateBox(collider, m_size.X, m_size.Y, m_size.Z);
 
             m_mass = m_density * m_size.X * m_size.Y * m_size.Z;  // update mass
 
@@ -758,9 +805,13 @@ namespace OpenSim.Region.Physics.OdePlugin
             Body = d.BodyCreate(_parent_scene.world);
 
             _zeroFlag = false;
+            m_collisionException = false;
             m_pidControllerActive = true;
             m_freemove = false;
 
+            _velocity = Vector3.Zero;
+            m_lastVelocitySqr = 0;
+
             d.BodySetAutoDisableFlag(Body, false);
             d.BodySetPosition(Body, npositionX, npositionY, npositionZ);
 
@@ -772,12 +823,14 @@ namespace OpenSim.Region.Physics.OdePlugin
             d.GeomSetBody(feetbox, Body);
             d.GeomSetBody(midbox, Body);
             d.GeomSetBody(topbox, Body);
-            d.GeomSetBody(bonebox, Body);
+            d.GeomSetBody(bbox, Body);
 
             d.GeomSetOffsetPosition(feetbox, 0, 0, feetz);
             d.GeomSetOffsetPosition(midbox, 0, 0, midz);
             d.GeomSetOffsetPosition(topbox, 0, 0, topz);
-            d.GeomSetOffsetPosition(bonebox, 0, 0, m_feetOffset);
+
+            ajustCollider();
+
 
             // The purpose of the AMotor here is to keep the avatar's physical
             // surrogate from rotating while moving
@@ -841,44 +894,109 @@ namespace OpenSim.Region.Physics.OdePlugin
             if (topbox != IntPtr.Zero)
             {
                 _parent_scene.actor_name_map.Remove(topbox);
-                _parent_scene.waitForSpaceUnlock(_parent_scene.CharsSpace);
+                _parent_scene.waitForSpaceUnlock(collider);
                 d.GeomDestroy(topbox);
                 topbox = IntPtr.Zero;
             }
             if (midbox != IntPtr.Zero)
             {
                 _parent_scene.actor_name_map.Remove(midbox);
-                _parent_scene.waitForSpaceUnlock(_parent_scene.CharsSpace);
+                _parent_scene.waitForSpaceUnlock(collider);
                 d.GeomDestroy(midbox);
                 midbox = IntPtr.Zero;
             }
             if (feetbox != IntPtr.Zero)
             {
                 _parent_scene.actor_name_map.Remove(feetbox);
-                _parent_scene.waitForSpaceUnlock(_parent_scene.CharsSpace);
+                _parent_scene.waitForSpaceUnlock(collider);
                 d.GeomDestroy(feetbox);
                 feetbox = IntPtr.Zero;
             }
 
-            if (bonebox != IntPtr.Zero)
+            if (bbox != IntPtr.Zero)
+            {
+                _parent_scene.actor_name_map.Remove(bbox);
+                _parent_scene.waitForSpaceUnlock(collider);
+                d.GeomDestroy(bbox);
+                bbox = IntPtr.Zero;
+            }
+
+            if (collider != IntPtr.Zero)
             {
-                _parent_scene.actor_name_map.Remove(bonebox);
-                _parent_scene.waitForSpaceUnlock(_parent_scene.CharsSpace);
-                d.GeomDestroy(bonebox);
-                bonebox = IntPtr.Zero;
+                d.SpaceDestroy(collider);
+                collider = IntPtr.Zero;
             }
 
         }
 
+        //in place 2D rotation around Z assuming rot is normalised and is a rotation around Z
+        public void RotateXYonZ(ref float x, ref float y, ref Quaternion rot)
+        {
+            float sin = 2.0f * rot.Z * rot.W;
+            float cos = rot.W * rot.W - rot.Z * rot.Z;
+            float tx = x;
+
+            x = tx * cos - y * sin;
+            y = tx * sin + y * cos;
+        }
+        public void RotateXYonZ(ref float x, ref float y, ref float sin, ref float cos)
+        {
+            float tx = x;
+            x = tx * cos - y * sin;
+            y = tx * sin + y * cos;
+        }
+        public void invRotateXYonZ(ref float x, ref float y, ref float sin, ref float cos)
+        {
+            float tx = x;
+            x = tx * cos + y * sin;
+            y = -tx * sin + y * cos;
+        }
+
+        public void invRotateXYonZ(ref float x, ref float y, ref Quaternion rot)
+        {
+            float sin = - 2.0f * rot.Z * rot.W;
+            float cos = rot.W * rot.W - rot.Z * rot.Z;
+            float tx = x;
+
+            x = tx * cos - y * sin;
+            y = tx * sin + y * cos;
+        }
+
+
         public bool Collide(IntPtr me, bool reverse, ref d.ContactGeom contact, ref bool feetcollision)
         {
             feetcollision = false;
+            if (m_collisionException)
+                return false;
 
-            if (me == bonebox) // inner bone
+            if (me == bbox) // if moving fast
             {
-                if (contact.pos.Z - _position.Z < boneOff)
-                    IsColliding = true;
-                return true;
+                // force a full inelastic collision
+                m_collisionException = true;
+
+                Vector3 off = m_size * 0.5f;
+                off.X += contact.depth;
+                off.Y += contact.depth;
+                off.Z += contact.depth;
+                if (reverse)
+                {
+                    off.X *= -contact.normal.X;
+                    off.Y *= -contact.normal.Y;
+                    off.Z *= -contact.normal.Z;
+                }
+                else
+                {
+                    off.X *= contact.normal.X;
+                    off.Y *= contact.normal.Y;
+                    off.Z *= contact.normal.Z;
+                }
+
+                off.X += contact.pos.X;
+                off.Y += contact.pos.Y;
+                off.Z += contact.pos.Z;
+
+                _position = off;
+                return false;
             }
 
             if (me == topbox) // keep a box head
@@ -890,6 +1008,21 @@ namespace OpenSim.Region.Physics.OdePlugin
 
             if (me == midbox)
             {
+                if (Math.Abs(contact.normal.Z) > 0.95f)
+                {
+                    float nz = contact.normal.Z;
+                    if (!reverse)
+                        nz = -nz;
+
+                    if (nz > 0)
+                        return true; // missed head TODO
+
+                    // missed feet collision?
+
+
+                    return true;
+                }
+
                 t = offx * offx + offy * offy;
                 t = (float)Math.Sqrt(t);
                 t = 1 / t;
@@ -917,12 +1050,19 @@ namespace OpenSim.Region.Physics.OdePlugin
 
                 if (Math.Abs(contact.normal.Z) > 0.95f)
                 {
+                    if (contact.normal.Z > 0)
+                        contact.normal.Z = 1.0f;
+                    else
+                        contact.normal.Z = -1.0f;
+                    contact.normal.X = 0.0f;
+                    contact.normal.Y = 0.0f;
                     feetcollision = true;
                     if (h < boneOff)
                         IsColliding = true;
                     return true;
                 }
 
+
                 float offz = h - feetOff; // distance from top of feetbox
 
                 if (offz > 0)
@@ -971,11 +1111,28 @@ namespace OpenSim.Region.Physics.OdePlugin
         /// This is the avatar's movement control + PID Controller
         /// </summary>
         /// <param name="timeStep"></param>
-        public void Move(float timeStep, List<OdeCharacter> defects)
+        public void Move(List<OdeCharacter> defects)
         {
             if (Body == IntPtr.Zero)
                 return;
 
+            if (m_collisionException)
+            {
+                d.BodySetPosition(Body,_position.X, _position.Y, _position.Z);
+                d.BodySetLinearVel(Body, 0, 0, 0);
+
+                float v = _velocity.Length();
+                if (v != 0)
+                {
+                    v = 6.0f / v;
+                    _velocity = _velocity * v;
+                    d.BodySetLinearVel(Body, _velocity.X, _velocity.Y, _velocity.Z);
+                }
+                ajustCollider();
+                m_collisionException = false;
+                return;
+            }
+
             d.Vector3 dtmp = d.BodyGetPosition(Body);
             Vector3 localpos = new Vector3(dtmp.X, dtmp.Y, dtmp.Z);
 
@@ -1049,6 +1206,7 @@ namespace OpenSim.Region.Physics.OdePlugin
 
             //******************************************
             // colide with land
+
             d.AABB aabb;
             d.GeomGetAABB(feetbox, out aabb);
             float chrminZ = aabb.MinZ - 0.02f; // move up a bit
@@ -1095,8 +1253,8 @@ namespace OpenSim.Region.Physics.OdePlugin
                         contact.Position.X = localpos.X;
                         contact.Position.Y = localpos.Y;
                         contact.Position.Z = chrminZ;
-                        contact.SurfaceNormal.X = 0f;
-                        contact.SurfaceNormal.Y = 0f;
+                        contact.SurfaceNormal.X = 0.0f;
+                        contact.SurfaceNormal.Y = 0.0f;
                         contact.SurfaceNormal.Z = -1f;
                         contact.RelativeSpeed = -vel.Z;
                         contact.CharacterFeet = true;
@@ -1118,6 +1276,7 @@ namespace OpenSim.Region.Physics.OdePlugin
                 m_iscollidingGround = false;
             }
 
+            
             //******************************************
 
             bool tviszero = (_target_velocity.X == 0.0f && _target_velocity.Y == 0.0f && _target_velocity.Z == 0.0f);
@@ -1253,21 +1412,58 @@ namespace OpenSim.Region.Physics.OdePlugin
             }
 
             // update our local ideia of position velocity and aceleration
+            //            _position = localpos;
             _position = localpos;
+
             if (_zeroFlag)
             {
                 _velocity = Vector3.Zero;
                 _acceleration = Vector3.Zero;
+                m_rotationalVelocity = Vector3.Zero;
             }
             else
             {
-                _acceleration = _velocity; // previus velocity
-                _velocity = vel;
-                _acceleration = (vel - _acceleration) / timeStep;
+                Vector3 a =_velocity; // previus velocity
+                SetSmooth(ref _velocity, ref vel, 2);
+                a = (_velocity - a) * invtimeStep;
+                SetSmooth(ref _acceleration, ref a, 2);
+
+                dtmp = d.BodyGetAngularVel(Body);
+                m_rotationalVelocity.X = 0f;
+                m_rotationalVelocity.Y = 0f;
+                m_rotationalVelocity.Z = dtmp.Z;
+                Math.Round(m_rotationalVelocity.Z,3);
             }
-          
+            ajustCollider();
         }
 
+        public void round(ref Vector3 v, int digits)
+        {
+            v.X = (float)Math.Round(v.X, digits);
+            v.Y = (float)Math.Round(v.Y, digits);
+            v.Z = (float)Math.Round(v.Z, digits);
+         }
+
+        public void SetSmooth(ref Vector3 dst, ref Vector3 value)
+        {
+            dst.X = 0.1f * dst.X + 0.9f * value.X;
+            dst.Y = 0.1f * dst.Y + 0.9f * value.Y;
+            dst.Z = 0.1f * dst.Z + 0.9f * value.Z;
+        }
+
+        public void SetSmooth(ref Vector3 dst, ref Vector3 value, int rounddigits)
+        {
+            dst.X = 0.4f * dst.X + 0.6f * value.X;
+            dst.X = (float)Math.Round(dst.X, rounddigits);
+
+            dst.Y = 0.4f * dst.Y + 0.6f * value.Y;
+            dst.Y = (float)Math.Round(dst.Y, rounddigits);
+
+            dst.Z = 0.4f * dst.Z + 0.6f * value.Z;
+            dst.Z = (float)Math.Round(dst.Z, rounddigits);
+        }
+
+
         /// <summary>
         /// Updates the reported position and velocity.
         /// Used to copy variables from unmanaged space at heartbeat rate and also trigger scene updates acording
@@ -1394,10 +1590,11 @@ namespace OpenSim.Region.Physics.OdePlugin
 
                     AvatarGeomAndBodyCreation(_position.X, _position.Y, _position.Z);
 
-                    _parent_scene.actor_name_map[topbox] = (PhysicsActor)this;
-                    _parent_scene.actor_name_map[midbox] = (PhysicsActor)this;
+                    _parent_scene.actor_name_map[collider] = (PhysicsActor)this;
                     _parent_scene.actor_name_map[feetbox] = (PhysicsActor)this;
-                    _parent_scene.actor_name_map[bonebox] = (PhysicsActor)this;
+                    _parent_scene.actor_name_map[midbox] = (PhysicsActor)this;
+                    _parent_scene.actor_name_map[topbox] = (PhysicsActor)this;
+                    _parent_scene.actor_name_map[bbox] = (PhysicsActor)this;
                     _parent_scene.AddCharacter(this);
                 }
                 else
@@ -1450,13 +1647,16 @@ namespace OpenSim.Region.Physics.OdePlugin
                                       _position.Z + (m_size.Z - oldsz) * 0.5f);
 
                     Velocity = Vector3.Zero;
+                    
 
-                    _parent_scene.actor_name_map[topbox] = (PhysicsActor)this;
-                    _parent_scene.actor_name_map[midbox] = (PhysicsActor)this;
+                    _parent_scene.actor_name_map[collider] = (PhysicsActor)this;
                     _parent_scene.actor_name_map[feetbox] = (PhysicsActor)this;
-                    _parent_scene.actor_name_map[bonebox] = (PhysicsActor)this;
+                    _parent_scene.actor_name_map[midbox] = (PhysicsActor)this;
+                    _parent_scene.actor_name_map[topbox] = (PhysicsActor)this;
+                    _parent_scene.actor_name_map[bbox] = (PhysicsActor)this;
                 }
                 m_freemove = false;
+                m_collisionException = false;
                 m_pidControllerActive = true;
             }
             else
@@ -1565,6 +1765,7 @@ namespace OpenSim.Region.Physics.OdePlugin
 
             if (Body != IntPtr.Zero)
                 d.BodySetLinearVel(Body, newmomentum.X, newmomentum.Y, newmomentum.Z);
+            ajustCollider();
         }
 
         private void donullchange()
@@ -1573,7 +1774,7 @@ namespace OpenSim.Region.Physics.OdePlugin
 
         public bool DoAChange(changes what, object arg)
         {
-            if (topbox == IntPtr.Zero && what != changes.Add && what != changes.Remove)
+            if (collider == IntPtr.Zero && what != changes.Add && what != changes.Remove)
             {
                 return false;
             }