When scaling the camera with the player, how can I make it more noticeable?

Question

I am making a game where you play as fish. When you eat food you become larger. I am counting the camera scale as follows:

camera.scale = (player.originalWidth / player.width)

Then I apply it as a transform to the whole world. Now when the fish grows up you don't see any change on your sprite, only on the surrounding world. I want to achieve that you will see the growing a little bit. How should I modify this equation?

Answer 1

Because making the fish actually occupy more screen space would eventually cause problems, you could instantly grow the fish, but then zoom the camera out over a couple seconds from the old zoom to the new zoom level. To zoom gradually you could use linear interpolation (often abbreviated 'lerp'), or you could use a logistic function to make the zoom smoother.

To do this, you would first store the current zoom level when a growth event happens:

oldScale = camera.scale;
newScale = player.originalWidth / player.width
zoomDuration = 500 // time it will take to zoom out in ticks
zoomElapsed = 0;

Then you would run a short function every tick to animate the zoom (here's how to do it with linear interpolation):

if(zoomElapsed < zoomDuration) {
  camera.scale = (zoomElapsed/zoomDuration)*(newScale-oldScale)+oldScale;
  zoomElapsed++;
} else {
  camera.scale = newScale;
}

And that would be it. Note that the linear interpolation above is going to 'jerk' into movement then instantly stop when it hits the new scale; to avoid that, the logistic curve would do nicely because it has tapered ends.