void IBeforeSolverUpdateable.Update(float dt)
        {
            //Someone may want to use the Body.CollisionInformation.Tag for their own purposes.
            //That could screw up the locking mechanism above and would be tricky to track down.
            //Consider using the making the custom tag implement ICharacterTag, modifying LockCharacterPairs to analyze the different Tag type, or using the Entity.Tag for the custom data instead.
            Debug.Assert(Body.CollisionInformation.Tag is ICharacterTag, "The character.Body.CollisionInformation.Tag must implement ICharacterTag to link the CharacterController and its body together for character-related locking to work in multithreaded simulations.");

            SupportData supportData;

            HorizontalMotionConstraint.UpdateMovementBasis(ref viewDirection);
            //We can't let multiple characters manage the same pairs simultaneously.  Lock it up!
            PairLocker.LockCharacterPairs();
            try
            {
                CorrectContacts();

                bool hadSupport = SupportFinder.HasSupport;

                SupportFinder.UpdateSupports(ref HorizontalMotionConstraint.movementDirection3d);
                supportData = SupportFinder.SupportData;


                //Compute the initial velocities relative to the support.
                Vector3 relativeVelocity;
                ComputeRelativeVelocity(ref supportData, out relativeVelocity);
                float verticalVelocity = Vector3.Dot(supportData.Normal, relativeVelocity);


                //Don't attempt to use an object as support if we are flying away from it (and we were never standing on it to begin with).
                if (SupportFinder.HasSupport && !hadSupport && verticalVelocity < 0)
                {
                    SupportFinder.ClearSupportData();
                    supportData = new SupportData();
                }


                //Attempt to jump.
                if (TryToJump)
                {
                    //In the following, note that the jumping velocity changes are computed such that the separating velocity is specifically achieved,
                    //rather than just adding some speed along an arbitrary direction.  This avoids some cases where the character could otherwise increase
                    //the jump speed, which may not be desired.
                    if (SupportFinder.HasTraction)
                    {
                        //The character has traction, so jump straight up.
                        float currentDownVelocity = Vector3.Dot(Down, relativeVelocity);
                        //Target velocity is JumpSpeed.
                        float velocityChange = Math.Max(jumpSpeed + currentDownVelocity, 0);
                        ApplyJumpVelocity(ref supportData, Down * -velocityChange, ref relativeVelocity);


                        //Prevent any old contacts from hanging around and coming back with a negative depth.
                        foreach (var pair in Body.CollisionInformation.Pairs)
                        {
                            pair.ClearContacts();
                        }
                        SupportFinder.ClearSupportData();
                        supportData = new SupportData();
                    }
                    else if (SupportFinder.HasSupport)
                    {
                        //The character does not have traction, so jump along the surface normal instead.
                        float currentNormalVelocity = Vector3.Dot(supportData.Normal, relativeVelocity);
                        //Target velocity is JumpSpeed.
                        float velocityChange = Math.Max(slidingJumpSpeed - currentNormalVelocity, 0);
                        ApplyJumpVelocity(ref supportData, supportData.Normal * -velocityChange, ref relativeVelocity);

                        //Prevent any old contacts from hanging around and coming back with a negative depth.
                        foreach (var pair in Body.CollisionInformation.Pairs)
                        {
                            pair.ClearContacts();
                        }
                        SupportFinder.ClearSupportData();
                        supportData = new SupportData();
                    }
                }
                TryToJump = false;


                //Try to step!
                Vector3 newPosition;
                //Note: downstepping is often not required.
                //It's only really there for games that expect to be able to run down stairs at 40 miles an hour without zipping off into the void.
                //Most of the time, you can just comment out downstepping, and so long as the character is running at a reasonable speed,
                //gravity will do the work.

                //If your game would work without teleportation-based downstepping, it's probably a good idea to comment it out.
                //Downstepping can be fairly expensive.

                //You can also avoid doing upstepping by fattening up the character's margin, turning it into more of a capsule.
                //Instead of teleporting up steps, it would slide up.
                //Without teleportation-based upstepping, steps usually need to be quite a bit smaller (i.e. fairly normal sized, instead of 2 feet tall).
                if (StepManager.TryToStepDown(out newPosition) ||
                    StepManager.TryToStepUp(out newPosition))
                {
                    supportData = TeleportToPosition(newPosition, dt);
                }

                if (StanceManager.UpdateStance(out newPosition))
                {
                    supportData = TeleportToPosition(newPosition, dt);
                }
            }
            finally
            {
                PairLocker.UnlockCharacterPairs();
            }

            //Tell the constraints to get ready to solve.
            HorizontalMotionConstraint.UpdateSupportData();
            VerticalMotionConstraint.UpdateSupportData();

            //Update the horizontal motion constraint's state.
            if (supportData.SupportObject != null)
            {
                float speed;
                switch (StanceManager.CurrentStance)
                {
                case Stance.Prone:
                    speed = proneSpeed;
                    break;

                case Stance.Crouching:
                    speed = crouchingSpeed;
                    break;

                default:
                    speed = standingSpeed;
                    break;
                }
                if (SupportFinder.HasTraction)
                {
                    HorizontalMotionConstraint.MovementMode = MovementMode.Traction;
                    HorizontalMotionConstraint.TargetSpeed  = speed;
                    HorizontalMotionConstraint.MaximumForce = tractionForce;
                }
                else
                {
                    HorizontalMotionConstraint.MovementMode = MovementMode.Sliding;
                    HorizontalMotionConstraint.TargetSpeed  = Math.Min(speed, slidingSpeed);
                    HorizontalMotionConstraint.MaximumForce = Math.Min(tractionForce, slidingForce);
                }
            }
            else
            {
                HorizontalMotionConstraint.MovementMode = MovementMode.Floating;
                HorizontalMotionConstraint.TargetSpeed  = airSpeed;
                HorizontalMotionConstraint.MaximumForce = airForce;
            }
            HorizontalMotionConstraint.TargetSpeed *= SpeedScale;
        }
        void IBeforeSolverUpdateable.Update(float dt)
        {
            //Someone may want to use the Body.CollisionInformation.Tag for their own purposes.
            //That could screw up the locking mechanism above and would be tricky to track down.
            //Consider using the making the custom tag implement ICharacterTag, modifying LockCharacterPairs to analyze the different Tag type, or using the Entity.Tag for the custom data instead.
            Debug.Assert(Body.CollisionInformation.Tag is ICharacterTag, "The character.Body.CollisionInformation.Tag must implement ICharacterTag to link the SphereCharacterController and its body together for character-related locking to work in multithreaded simulations.");

            SupportData supportData;

            HorizontalMotionConstraint.UpdateMovementBasis(ref viewDirection);
            //We can't let multiple characters manage the same pairs simultaneously.  Lock it up!
            PairLocker.LockCharacterPairs();
            try
            {
                bool hadSupport = SupportFinder.HasSupport;

                SupportFinder.UpdateSupports(ref HorizontalMotionConstraint.movementDirection3d);
                supportData = SupportFinder.SupportData;

                //Compute the initial velocities relative to the support.
                Vector3 relativeVelocity;
                ComputeRelativeVelocity(ref supportData, out relativeVelocity);
                float verticalVelocity = Vector3.Dot(supportData.Normal, relativeVelocity);



                //Don't attempt to use an object as support if we are flying away from it (and we were never standing on it to begin with).
                if (SupportFinder.HasSupport && !hadSupport && verticalVelocity < 0)
                {
                    SupportFinder.ClearSupportData();
                    supportData = new SupportData();
                }



                //Attempt to jump.
                if (tryToJump) //Jumping while crouching would be a bit silly.
                {
                    //In the following, note that the jumping velocity changes are computed such that the separating velocity is specifically achieved,
                    //rather than just adding some speed along an arbitrary direction.  This avoids some cases where the character could otherwise increase
                    //the jump speed, which may not be desired.
                    if (SupportFinder.HasTraction)
                    {
                        //The character has traction, so jump straight up.
                        float currentDownVelocity;
                        Vector3.Dot(ref down, ref relativeVelocity, out currentDownVelocity);
                        //Target velocity is JumpSpeed.
                        float velocityChange = Math.Max(jumpSpeed + currentDownVelocity, 0);
                        ApplyJumpVelocity(ref supportData, down * -velocityChange, ref relativeVelocity);


                        //Prevent any old contacts from hanging around and coming back with a negative depth.
                        foreach (var pair in Body.CollisionInformation.Pairs)
                        {
                            pair.ClearContacts();
                        }
                        SupportFinder.ClearSupportData();
                        supportData = new SupportData();
                    }
                    else if (SupportFinder.HasSupport)
                    {
                        //The character does not have traction, so jump along the surface normal instead.
                        float currentNormalVelocity = Vector3.Dot(supportData.Normal, relativeVelocity);
                        //Target velocity is JumpSpeed.
                        float velocityChange = Math.Max(slidingJumpSpeed - currentNormalVelocity, 0);
                        ApplyJumpVelocity(ref supportData, supportData.Normal * -velocityChange, ref relativeVelocity);

                        //Prevent any old contacts from hanging around and coming back with a negative depth.
                        foreach (var pair in Body.CollisionInformation.Pairs)
                        {
                            pair.ClearContacts();
                        }
                        SupportFinder.ClearSupportData();
                        supportData = new SupportData();
                    }
                }
                tryToJump = false;
            }
            finally
            {
                PairLocker.UnlockCharacterPairs();
            }


            //Tell the constraints to get ready to solve.
            HorizontalMotionConstraint.UpdateSupportData();
            VerticalMotionConstraint.UpdateSupportData();



            //Update the horizontal motion constraint's state.
            if (supportData.SupportObject != null)
            {
                if (SupportFinder.HasTraction)
                {
                    HorizontalMotionConstraint.MovementMode = MovementMode.Traction;
                    HorizontalMotionConstraint.TargetSpeed  = speed;
                    HorizontalMotionConstraint.MaximumForce = tractionForce;
                }
                else
                {
                    HorizontalMotionConstraint.MovementMode = MovementMode.Sliding;
                    HorizontalMotionConstraint.TargetSpeed  = slidingSpeed;
                    HorizontalMotionConstraint.MaximumForce = slidingForce;
                }
            }
            else
            {
                HorizontalMotionConstraint.MovementMode = MovementMode.Floating;
                HorizontalMotionConstraint.TargetSpeed  = airSpeed;
                HorizontalMotionConstraint.MaximumForce = airForce;
            }
            HorizontalMotionConstraint.TargetSpeed *= SpeedScale;
        }