How can I get a 30 or 60 frame rate when using QGLWidget? QTimer is not acurate

[ricardo]

What you're running into is a limitation of the (type of) operating system. OSes made for people aren't too strict on timing because there is no need for it.

Also remember two things:

1. Debug mode generally makes your app slower
2. Outputting stuff to console makes your app slower

Thanks for reply.

I did that, relese mode and not writing anything on console. I wrote this test code:

void CEditor::TimerFired() {
	static int rendered_frames=0;
	// draw here whatever
	m_current_level->Update(0);
	m_gl_drawer->updateGL();
	rendered_frames++;
 
	// after 10 seconds
	int total_time=10000;
	if (m_time.elapsed()>total_time) {
		float fps=rendered_frames/(0.001*total_time);
		QString m=QString("FPS: %1. rendered frames: %2. Timer interval (ms): %3. Total time (ms): %4").arg(fps).arg(rendered_frames).arg(SIMULATION_UPDATE_INTERVAL_IN_MS).arg(total_time);
		QMessageBox::warning(this, "Warning", m);
		m_timer->stop();
	}
}

void CEditor::TimerFired() {
	static int rendered_frames=0;
	// draw here whatever
	m_current_level->Update(0);
	m_gl_drawer->updateGL();
	rendered_frames++;

	// after 10 seconds
	int total_time=10000;
	if (m_time.elapsed()>total_time) {
		float fps=rendered_frames/(0.001*total_time);
		QString m=QString("FPS: %1. rendered frames: %2. Timer interval (ms): %3. Total time (ms): %4").arg(fps).arg(rendered_frames).arg(SIMULATION_UPDATE_INTERVAL_IN_MS).arg(total_time);
		QMessageBox::warning(this, "Warning", m);
		m_timer->stop();
	}
}

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That code will simulate my game for just 10 seconds. 20 ms interval (SIMULATION_UPDATE_INTERVAL_IN_MS) should be 50 frames per sencod. As you can see in this picture, something is wrong.



So, what do you recommend me? Does anyone know why this happens?

Thanks a lot.