Simple framerate counter?

Question

I'm making a first person shooter, and I've seen questions like this before, but the answer is either overly complicated or they're using SDL, GLFW, GLUT, or something else. I'm not using any of that. OpenGL, C++, and GLEW for me.

I am just a little confused on how to do a framerate counter, so if I could get pseudo-code or some code-snippets that would point me in the right direction, that would help.

Answer 1

To measure framerate you need two counts:

• How many frames (not draw calls) have passed, and,
• How much time has passed.

Your framerate is therefore calculated as:

frames / time

There are a few subtle complexities to this.

First thing is that you need a good, accurate, high resolution timer. You don't say what platform you're on so I'm not going to make any assumptions beyond:

• You have such a timer available, and,
• You're not using Sleep calls to control framerate (if you are, stop it now).

Let's say that you're storing the time in a variable called "timepassed". It's a double and it starts at 0 and counts the time (in seconds) since the game started. Our framerate counter begins like this:

static int frames = 0;
static double starttime = 0;
static bool first = TRUE;
static float fps = 0.0f;

The first thing we do is check if this is the first time we've passed through the counter and set some stuff up:

if (first)
{
    frames = 0;
    starttime = timepassed;
    first = FALSE;
    return;
}

Next we increment the number of frames that have passed; I'm assuming here that you're updating the framerate counter once per frame only:

frames++;

And here we evaluate the actual FPS number.

if (timepassed - starttime > 0.25 && frames > 10)
{
    fps = (double) frames / (timepassed - starttime);
    starttime = timepassed;
    frames = 0;
}

Here we update the FPS count every 0.25 seconds. This isn't strictly speaking necessary but otherwise if you have a variable framerate you're going to be getting numbers wildly flashing on your screen and you won't be able to read them too good. (It's also important that timepassed - starttime is greater than 0.) After calculating the FPS we then update our static variables for the next pass through.

This is prety much my standard FPS counter (it's C heritage shows in some of the code) and I've cross-checked it with the values provided by FRAPS and found it highly accurate.

Answer 2

Since you are using SLD then the first thing to do is look up SDL_GetTicks();

Obviously it's very easy to figure out what to display on your counter from there but you need to actually display it, too.

Generally you want to use something like FreeType to allow you to load entire font sets. This gives you a great deal of information about each "glyph", which represents a single character; and additionally allowing you to create a texture or textures full of your glyphs.

http://www.learnopengl.com/#!In-Practice/Text-Rendering

This tutorial takes you through the basics.