From: stormreaver
Written: 2010-04-02 13:33:10.50897
Subject: Calculating Frames Per Second

Calculating the frames per second for display purposes is very simple. The basic idea is that you want to calculate the fraction of a second that was required to render the frame, then invert it to a whole number.

In your main game loop:

1) Get the starting time (I use microseconds) before processing your frame.

2) Process your frame.

3) Get the ending time (again, I use microseconds) after processing your frame.

4) Calculate the elapsed time (ending time minus starting time).

5) The fraction of a second that it took to render the frame is 1 / elapsed time. This is a decimal number like 0.25.

6) Now the decimal needs to be converted to a whole number. This is 1/decimal number. For example: if your frame rendered in 0.25 seconds, then your loop runs at 4 frames per second (1/0.25 equals 4).

Steps 5 and 6 can be combined into a single calculation:

fps = 1 / (1 / elapsed time)
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