Question

Playing Starcraft, I was just wondering how to achieve the same effect as they do when bringing their buttons on screen. (0:20 into this video - http://www.youtube.com/watch?v=r4ijwtGCaRg).

I tried doing position.x += 5, but how do I get it to move less towards the end like how the buttons slows down?

Answer 1

All you need to do is make 5 smaller the closer you get to your final position. This can be done several ways. I'm not sure on what may be the most efficient though. It also depends on what the rest of the code is doing.One way is this.

if( position.x < finalPos.x * 0.6f)

   position.x += 5;     // Move normal speed until 60% of way to final position

else if( position.x < finalPos.x)

   position.x += 2;     // Move slower to final position

This only works when moving in the positive direction and you start at 0, though. You could also try making the 5 a number that gets smaller the closer the position gets to the end.

position.x = (finalPos.x - position.x) * 0.6f; 
//Move 60% of the way to final position.

As long as you get the idea you can make it fit what you need. Hope I helped.

Answer 2

In pseudo code:

// Make the object fly out to the right
speed = 0;   
while(position.x < screen.width)
   position.x += speed;
   speed += 0.1;


// Or, make the object fly in from the right
speed = 5;
while(position.x > target.x)
    position.x -= speed;
    speed -= 0.1;

Something along those lines should give you the smoothness you're after.

Answer 3

This sounds like a perfect use for a sine wave to me!

Answer 4

What you have is called dampening. You stop giving a constant velocity to the object, let its current velocity take over, and apply friction.

Or just use flash.