Inaccurate time intervals for a Metronome

Processing
10

Using TimerTask or another Thread for this is a daft idea that’s just going to tie the OP in knots trying to get things to synchronize. Please note the “I’m new to Processing” - consider half the seasoned developers on here can’t do multi-threaded programming right! :wink:

There are a few things wrong with the initial code, but not that can’t easily be fixed. Try -

int c = 0;

float bpm = 120;
long interval = (long) (1e9 / (bpm / 60));
long nextTime;

void setup() {
  size(600, 600);
  nextTime = System.nanoTime() + interval;
}

void draw()  {
  background(0);
  if(System.nanoTime() >= nextTime)  {
    nextTime = nextTime + interval;
    c = 255;
  }
  if (c > 0) {
    fill(c);
    ellipse(width/2, height/2, height/2 + 0.016*height, height/2 + 0.016*height);
    c -= 30;
  }
}

Note

  • Don’t use floats for time - keep it in longs
  • Make sure you follow @MxFxM advice about time >= nextTime, but you don’t need temp, because …
  • To get fixed rate you need to add the interval to your previous nextTime, not the current time, otherwise you accumulate errors.
  • I needed to add the if (c > 0) section to animate down the fill colour, or sometimes the default renderer output doesn’t show for me - seems some calls to draw() don’t make it on screen! (I repurposed your count variable for this :smile: )
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