Interpolation between numbers - Libgdx

Newbie & Debugging Questions
#1

I’m trying to implement a simple “counting numbers” animation in my game. I want that whenever the score is changed, the numbers will start to count up/down until they have reached the desired number.

I tried to implement this by doing this:

points = new Label(""+ScoreManager.getPlayerScore(), skin, "default-nice") {
			private float target, rendered;
			public void act(float delta) {
				super.act(delta);
				target = ScoreManager.getPlayerScore();
                rendered = rendered < target ? Interpolation.linear.apply(rendered, target, 0.05f) : Interpolation.linear.apply(target, rendered, 0.05f);
                setText("" + MathUtils.ceil(target));
			}
		};

But it has no affect. The numbers are still changed suddently.

P.S I have one more question, not related to this topic - How can I define a fixed position to a table? I set a position for a table in my game but it can changed according to its children’s width and height.

#2

You can only set the absolute positions of tables of they are added to the parent without a cell.

So rather than add(), use addActor(). For nice little animations, check out scene2d actions and the Interpolation class.

#3

The Interpolation alpha parameter is from 0 to 1. For your situation, use x/y where x is the amount of time since the score changed and y is how long the you want the visual score change to take.

#4

I’m sorry but I didn’t quite understand what you said. Could you please elaborate about that?

#5 

float time = 0;
float duration = 3;
int lastScore = 123;
int actualScore = 456;
while (time < duration) {
	float alpha = Math.min(1, time / duration);
	int visualScore = (int)Interpolation.pow2Out.apply(lastScore, actualScore, alpha);
	System.out.println(visualScore);
	time += 0.032;
}

Once you understand that, apply it to your game. Set time=0 when the score changes, increment time each frame. Pro tip: when score changes, clear actions, then add a TemporalAction that adjusts the visual score.

#6

Thanks for your help. I tried what you said but I keep failing to get it to work properly. Here is my code:

points = new Label("0", skin, "default-nice") {
			private final float duration = 3;
			private float time = 0, alpha;
			private int lastScore, actualScore, visualScore;
			public void act(float delta) {
				super.act(delta);
				lastScore = Integer.parseInt(points.getText().toString());
				actualScore = hudManager.getListener().getPlayerScore();
				if(time<duration) {
					alpha = Math.min(1, time / duration);
					visualScore = (int)Interpolation.pow2Out.apply(lastScore, actualScore, alpha);
					setText(""+visualScore);
					time += 0.010;
				} else {
					lastScore = actualScore;
				}
			}
		};

Right now whenever the player score changes, the visual score remains “0”.

Edit: Nevermind, I got it! Thanks for your help, Nate! Here is my new-working code:

points = new Label("0", skin, "default-nice") {
			private final float duration = 0.5f;
			private float time = 0, alpha;
			private int lastScore = 0, actualScore, visualScore;
			public void act(float delta) {
				super.act(delta);
				actualScore = hudManager.getListener().getPlayerScore();
				if(actualScore != lastScore) {
					if(time<duration) {
						alpha = Math.min(1, time / duration);
						visualScore = (int)Interpolation.pow2Out.apply(lastScore, actualScore, alpha);
						setText(""+visualScore);
						time += 0.010;
					} else {
						lastScore = actualScore;
						time = 0;
					}
				}
			}
		};
#7

Great! Though “time += 0.010;” should be “time += delta;”.