How do you measure fps?

[brollysan]

How do you guys display FPS to the screen?

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int fps = 60; t0 = system.nanoTime(); //...lots of rendering //.. //.. t1 = system.nanoTime(); long delta = ((1E+9)*1.0/fps) - (t1-t0); g.drawString("FPS:"+ (1E+9)*1.0/delta, 0,0); buffer.show(); //Sleep Thread.sleep(delta)

This is how I currently do it and there are so many problems with it:

• Delta may be negative due to bad resolution
• Delta does NOT take into account time spent calling g.drawstring and buffer.show
• The sleep may be accurate within margins of error by calling system.nanoTime() inside sleep() but this makes for inaccurate display
• If t1 is too long delta becomes negative. Do you play catchup with the framerate by sleeping a shorter time next iteration?

I see no way of circumventing the second point, display to console would be much easier, you could wrap all of it in a method, measure time between each method-calls and print it to console. But any displayed FPS must take the delta THEN display it.

[kramin42]

For your second point you can do this (making sure to initialise t0 to something):

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int fps = 60; //...lots of rendering //.. //.. t1 = system.nanoTime(); long delta = ((1E+9)*1.0/fps) - (t1-t0); t0 = system.nanoTime(); g.drawString("FPS:"+ (1E+9)*1.0/delta, 0,0); buffer.show(); //Sleep Thread.sleep(delta)

I usually just literally count the number of frames it displays in a second (the fps gets updated every second).

[ags1]

I just count the number of times per second the GLEventListener.display() method is called. And I use System.currentTimeMillis() - with each frame 16 - 40 ms to render I don't think precision is that much of an issue.