Why does my sprite animation sometimes runs faster? [closed]

Question

I don't know why each time I call the Update_Animation function, my sprite animation runs faster. Is it caused by gameTime? How to fix it?

Here's the relevant code:

class Character
{
    // <SNIP>

    public void Update_Animation(Point sheetSize, TimeSpan frameInterval, GameTime gameTime)
    {
        if (nextFrame >= frameInterval)
        {
            currentFrame.X++;

            if (currentFrame.X >= sheetSize.X)
            {
                currentFrame.X = 0;
                currentFrame.Y++;
            }

            if (currentFrame.Y >= sheetSize.Y)
                currentFrame.Y = 0;

            nextFrame = TimeSpan.Zero;
        }
        else
        {
            nextFrame += gameTime.ElapsedGameTime;
        }
    }  

    // <SNIP>

    private void UpdateMovement(KeyboardState aCurrentKeyboardState, GameTime gameTime)
    {
        if (mCurrentState == State.Walking)
        {
            action = "stand";
            Update_Animation(sheetSize_Stand, frameInterval_Stand, gameTime);

            mSpeed = Vector2.Zero;
            mDirection = Vector2.Zero;

            if (aCurrentKeyboardState.IsKeyDown(Keys.Left) && !aCurrentKeyboardState.IsKeyDown(Keys.Right))
            {
                action = "run";
                effect = SpriteEffects.None;

                mSpeed.X = CHARACTER_SPEED;
                mDirection.X = MOVE_LEFT;

                Update_Animation(sheetSize_Run, frameInterval_Run, gameTime);
            }
            else if (aCurrentKeyboardState.IsKeyDown(Keys.Right) && !aCurrentKeyboardState.IsKeyDown(Keys.Left))
            {
                action = "run";
                effect = SpriteEffects.FlipHorizontally;

                mSpeed.X = CHARACTER_SPEED;
                mDirection.X = MOVE_RIGHT;

                Update_Animation(sheetSize_Run, frameInterval_Run, gameTime);
            }

            if (aCurrentKeyboardState.IsKeyDown(Keys.Z) && mPreviousKeyboardState.IsKeyUp(Keys.Z))
            {
                mCurrentState = State.Hitting;
            }
        }

        if (mCurrentState == State.Hitting)
        {
            action = "hit";

            Update_Animation(sheetSize_Hit, frameInterval_Hit, gameTime);
            mCurrentState = State.Walking;
        }
    }

    // <SNIP>
}

Answer 1

Your description is a bit vague, and you pasted way too much code... but I think the problem lies in the Update_Animation method:

You increase the value of nextFrame multiple times in an update if your character is running or 'hitting'.

Either make sure you call the Update_Animation method only once in an update, or just don't use the same variable (nextFrame) for all calls.

Answer 2

It seems like your Update_Animation method is called every Update or Draw call. That means that your animation speed depends on your computer's speed. On slow computers, animation is slow; on fast computers, animation is slow.

What you probably want with XNA is the game (and as much as possible, the UI) to run independently of the actual speed the game is executed.

What this boils down to (and the way I solved this in the past -- for animation, velocity/physics, etc.) is to update on a certain interval, i.e.

if ((DateTime.Now - lastFrameUpdate).TotalSeconds <= updateInterval) {
  Update_Animation(...)
  lastFrameUpdate = DateTime.Now;
}

In my case, I used a configurable interval like TimeSpan.FromSeconds(0.1).TotalSeconds to indicate frames should be updated every tenth of a second.