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// limits the FPS
void LimitFPS( int max_fps )
{
	// from http://www.geisswerks.com/ryan/FAQS/timing.html

	// timer must be at a resolution of 1ms at the start of this code

	// the time since the last frame
	static LARGE_INTEGER m_prev_end_of_frame = {0};

	// the timer frequency and counter
	LARGE_INTEGER m_high_perf_timer_freq,t;

	// get the frequency
	if( !QueryPerformanceFrequency( &m_high_perf_timer_freq ) )
		m_high_perf_timer_freq.QuadPart = 0;

	// get the counter
	QueryPerformanceCounter(&t);

	// make sure the frame has been initialized
	if (m_prev_end_of_frame.QuadPart != 0)
	{
		// how many ticks do we need to wait for?
		int ticks_to_wait = (int)m_high_perf_timer_freq.QuadPart / max_fps;

		// done yet
		int done = 0;

		// main wait loop
		do
		{
			// get the time
			QueryPerformanceCounter(&t);

			// how many ticks have passed?
			int ticks_passed = (int)((__int64)t.QuadPart - (__int64)m_prev_end_of_frame.QuadPart);

			// how many ticks left?
			int ticks_left = ticks_to_wait - ticks_passed;

			// check if time has wrapped
			if (t.QuadPart < m_prev_end_of_frame.QuadPart)    // time wrap
				done = 1;

			// same as above
			if (ticks_passed >= ticks_to_wait)
				done = 1;

			// if not done, give up the timeslice
			if (!done)
			{
				// > 0.002 seconds left, sleep for some time
				// saves CPU time and hence laptop battery power
				if (ticks_left > (int)m_high_perf_timer_freq.QuadPart*2/1000)
					Sleep(1);
				else                        
					for ( int i=0; i < 10; i++ ) 
						Sleep(0);
			}
		}
		while (!done);
	}

	// either way, the end of the frame has to be NOW
	m_prev_end_of_frame = t;
}