You using delta timing.
Getting it right is quite hard. So this is expected when you use delta.
Either learn really about gameloops and delta timesteps, or dont use delta - it depends on what you target
am kinda having the same problem, my game looks a little bit flickering even in 60FPS and am using Delta (same code i found in the LWJGL wiki ) so i want to ask you, what do you mean by it depends on what you target ? and is it possible to use a different game loop ?
Yes absolutely. You can just do your game frame-based.
Time/Delta vs Frame based game loops are, at least in the indie area a holy war...
The frame based approach is simply: Make sure your game runs a rock solid framerate, eg 60fps and dont use delta. Or have too modes 30 and 60.
Many many games are like this, since you dont have to use delta if you are sure that your framerate is constant, which is a good thing anyway.
However it kinda depends what platform you target and what your game is like.
If you are using a platform like say a console, you can easily use frame-based, since it will run the same anywhere.
And it also depends on what is going on in your game... If there are really busy sections and really idle sections you may have to use some delta.
Of our 4 games, 3 use frame-based and one uses some delta by applying a low pass filter over the delta values and stuff... Its really hard to get it right.
But if your game has like a minimum system requirement and you cap the fps, the game will only run slower on hardware that is simply too slow anyway.
So yeah I'm kinda frame-based.
To me, the problems you encounter with using delta far exceed the benefits in most cases.