xna - How to create simple acceleration in a 2D sprite?

So here's what I thought might work but half the time I press the 'Right' key, it results in a crash and the rest of the time seems to produce no acceleration at all.

if (KeyboardState.IsKeyDown(Keys.Right))

            while (motion.X < 1)
                motion.X += 0.001f + motion.X;

I want to know why exactly it won't work, and any possible alternate algorithms.

Answer

To implement basic acceleration you need to know a little physics. The basics you need to know about are the relationships between:

• Position - Where your object is


• Velocity - The direction and rate your object is changing its position


• Acceleration - The direction and rate your object is changing its velocity

So, to add acceleration, you need to have Position and Velocity already implemented. I'll assume you're doing that already, since you're asking about Acceleration.

Since you have velocity already implemented, I'll assume you have something like:

player.x += player.velocity.x * dt;
player.y += player.velocity.y * dt;

Where dt is the time since the last update. Now if we want to change the velocity with respect to time, we just need to add a line like this:

player.velocity.x += player.acceleration.x * dt;
player.velocity.y += player.acceleration.y * dt;

Now, if we want to modify that acceleration with the keyboard, we can do something simple like:

if (KeyboardState.IsKeyDown(Keys.Right))

    player.acceleration.x += .01f;