RDTSC x86 instruction: starting with Pentium processor, it was possible to get the timestamp 64 bit value using a single instruction that returns the number of clock cycles since the CPU was powered up.Using the 8253 timer chip (PIT): Michael Abrash, in his masterpiece Graphics Programming Black Book, explained how he could get a 1μs precision, more than 20 years ago!.Game developers have faced this problem since the '80s: In this article, "measuring time" means interval timing we are focused mainly on measuring elapsed time between two events. Each solution has pros and cons, and in this article I will discuss the possible ways of measuring time on an Android device in an accurate and efficient way.
Hardware timers exist in every device (and are different from device to device), the Android operating system offers different timers, and finally Java itself offers more then one timer. It is confusing to choose the right tool for measuring time. to achieve constant game speed independent of variable FPS.to calculate FPSs of interactive software, in an accurate and possibly efficient way.It is to measure this kind of variation and the code should handle variable FPS in order to get a constant game speed, so that the user experience will be the same if the frame rate will drop down from 60FPS to 30FPS.Įvery game developer knows how it is important to measure time in applications, for example: In this world, the developer cannot make any assumption even the interval between two consecutive frames can vary at any moment - for example, scenes with more objects will slow down the rendering process and the time interval between two consecutive frames will be longer. Let's think about an OpenGL ES game running at 60 frames per second (quite common on an average Android smartphone) we have only 16 milliseconds between two frames, this means that all the magic behind the rendering of a frame happens in this time slice.īetween two frames exists a different world, where the concept of time has a totally different meaning in this world, the only acceptable units of measurement are micro or nanoseconds.
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