CODEWITHSUNDEEP
javamathtimedelta
WEDEBE
WEDEBE

Reputation: 148

Calculating elapsed time using delta

I must be making some silly mistake in my code, In my head this should work but the timer works a bit too fast ( I want to get time left in seconds).

My code:

timeElapsed = 0;
timeLeft = 60;
//delta = time it took to get through one frame (60 fps). 

timeElapsed += delta/getFramesPerSecond(); //FPS = 60f
timeLeft -= timeElapsed; //timeLeft starts at 60 (seconds)
timeDisplay = "Time left: " + timeLeft;

I have checked that FPS is always 60, what am I missing here?

Delta sample prints: 

0.016969847
0.017038532
0.017123796
0.017026689
0.016969848
0.017059453
0.01697774
0.016987609
0.017073665
0.017035767
0.01708432

Upvotes: 1

Views: 717

Answers (1)

Lutz Lehmann
Lutz Lehmann

Reputation: 25972

timeElapsed+timeLeft should be a constant (thus both should change by the same amount in opposite directions), however, you are repeatedly reducing timeLeft by timeElapsed

In a demonstrative example with steps 1 in timeElapsed, your code gives

timeElapsed   timeLeft
    0            60
    1            59
    2            57
    3            54
    4            50
    5            45
    6            39
    7            32

Change the code to

timeDelta    = delta/getFramesPerSecond(); 
timeElapsed += timeDelta; 
timeLeft    -= timeDelta; 
timeDisplay  = "Time left: " + timeLeft;

Upvotes: 1

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