Using elapsed time for SlowMo in XNA
- by Dave Voyles
I'm trying to create a slow-mo effect in my pong game so that when a player is a button the paddles and ball will suddenly move at a far slower speed. I believe my understanding of the concepts of adjusting the timing in XNA are done, but I'm not sure of how to incorporate it into my design exactly.
The updates for my bats (paddles) are done in my Bat.cs class:
/// Controls the bat moving up the screen
/// </summary>
public void MoveUp()
{
SetPosition(Position + new Vector2(0, -moveSpeed));
}
/// <summary>
/// Controls the bat moving down the screen
/// </summary>
public void MoveDown()
{
SetPosition(Position + new Vector2(0, moveSpeed));
}
/// <summary>
/// Updates the position of the AI bat, in order to track the ball
/// </summary>
/// <param name="ball"></param>
public virtual void UpdatePosition(Ball ball)
{
size.X = (int)Position.X;
size.Y = (int)Position.Y;
}
While the rest of my game updates are done in my GameplayScreen.cs class (I'm using the XNA game state management sample)
Class GameplayScreen
{
...........
bool slow;
..........
public override void Update(GameTime gameTime, bool otherScreenHasFocus, bool coveredByOtherScreen)
base.Update(gameTime, otherScreenHasFocus, false);
if (IsActive)
{
// SlowMo Stuff
Elapsed = (float)gameTime.ElapsedGameTime.TotalSeconds;
if (Slowmo) Elapsed *= .8f;
MoveTimer += Elapsed;
double elapsedTime = gameTime.ElapsedGameTime.TotalMilliseconds;
if (Keyboard.GetState().IsKeyDown(Keys.Up))
slow = true;
else if (Keyboard.GetState().IsKeyDown(Keys.Down))
slow = false;
if (slow == true)
elapsedTime *= .1f;
// Updating bat position
leftBat.UpdatePosition(ball);
rightBat.UpdatePosition(ball);
// Updating the ball position
ball.UpdatePosition();
and finally my fixed time step is declared in the constructor of my Game1.cs Class:
/// <summary>
/// The main game constructor.
/// </summary>
public Game1()
{
IsFixedTimeStep = slow = false;
}
So my question is:
Where do I place the MoveTimer or elapsedTime, so that my bat will slow down accordingly?
