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copied!<p>Your FPS may (and usually will) vary, so counting frames is not a great idea.</p> <p>Assume this example to see how this could bite you:<br> Your application runs vsynced to 60 FPS, and your frame time is 16.58ms. That means to have the object on screen for 2 seconds, you will have to draw your object for 120 frames. Easy, let's go!<br> Drawing the object adds 0.1 ms, giving a total frame time of 16.68ms. Oh sh*t. Now you have 30 FPS, and your object shows for 4 seconds...</p> <p>Use <strong>proper time</strong> to decide whether or not to draw your object. When you've reached the conclusion that your object's time is up, just set a flag so you won't draw it (or, remove it from the scenegraph, if you have one, or delete it, or whatever).</p> <p>This can be done in a variety of ways:</p> <ul> <li>Under Windows <ul> <li>Use <code>SetTimer</code>, which will post a message to your window's message queue. When you receive the WM_TIMER notification, set the object's <code>do_draw</code> flag (or whatever you want to call it) to false.</li> <li>If you already use <code>WaitFor(Single|Multiple)Object</code> somewhere once every frame, do a <code>CreateWaitableTimer</code>, and wait on this as well. You can use <code>MsgWaitForMultipleObjectsEx</code> to do the message pumping and waiting in one go, and check APCs at the same time.</li> <li>Nothing prevents you from reading time manually once per frame. <code>GetTickCount</code> once, add 2000, and do an <code>if(new_count <= old_count + 2000) draw_object()</code>. While the accuracy of <code>GetTickCount</code> is abysmal (several dozens of milliseconds), this does not matter at all when waiting for 2 seconds.</li> </ul></li> <li>Under Linux <ul> <li>Use a <code>timerfd</code> and an <code>epoll</code> to check readiness, or set the <code>timerfd</code> it to nonblocking and see whether reading from it returns EAGAIN</li> <li>Use <code>clock_gettime</code> and do it manually (as with <code>GetTickCount</code>)</li> <li>Use <code>setitimer</code></li> </ul></li> </ul>

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