Tile based movement jerky with fixed time step.

I would like to redo my old method to work smoothly with the default fixed time step and am looking for ideas on how to accomplish this. The tile based movement I'm talking about is the same used in many old console rpg's (FF4/FF5/FF6) where the player moves a complete tile before accepting movement input again, yet still smoothly moves to it's destination (as opposed to jumping directly to each tile).

Here's my old method converted to XNA.

//
Vector2 position = new Vector2(32, 32);
Vector2 destination = position;
float speed = 128;

public void Update(KeyboardState keyState, float elapsed)
{
switch (state)
{
case State.Idle:
if (keyState.IsKeyDown(Keys.Up))
{
destination.Y -= 32;
state = State.MoveUp;
direction = Direction.Up;
}

else if (keyState.IsKeyDown(Keys.Down))
{
destination.Y += 32;
state = State.MoveDown;
direction = Direction.Down;
}

else if (keyState.IsKeyDown(Keys.Left))
{
destination.X -= 32;
state = State.MoveLeft;
direction = Direction.Left;
}

else if (keyState.IsKeyDown(Keys.Right))
{
destination.X += 32;
state = State.MoveRight;
direction = Direction.Right;
}
break;

case State.MoveUp:
moveUp(elapsed);
break;

case State.MoveDown:
moveDown(elapsed);
break;

case State.MoveLeft:
moveLeft(elapsed);
break;

case State.MoveRight:
moveRight(elapsed);
break;
}
}

void moveUp(float elapsed)
{
if (position.Y - speed * elapsed < destination.Y)
{
position.Y = destination.Y;
state = State.Idle;
}
else
position.Y -= speed * elapsed;
}

void moveDown(float elapsed)
{
if (position.Y + speed * elapsed > destination.Y)
{
position.Y = destination.Y;
state = State.Idle;
}
else
position.Y += speed * elapsed;
}

void moveLeft(float elapsed)
{
if (position.X - speed * elapsed < destination.X)
{
position.X = destination.X;
state = State.Idle;
}
else
position.X -= speed * elapsed;
}

void moveRight(float elapsed)
{
if (position.X + speed * elapsed > destination.X)
{
position.X = destination.X;
state = State.Idle;
}
else
position.X += speed * elapsed;
}
//

With XNA's default 16.6666 timestep, moving produces a slight pause each time the player transitions between tiles. I'm looking for a more effecient way to handle tile based movement while keeping this default timestep.

Any ideas are welcome.

[14093 byte] By [Apathy] at [2007-12-24]