Fullscreen decreases performance

FumarMata · Post by **FumarMata** » Wed Mar 21, 2007 11:10 am

Hello

Do you know why fullscreen decreases my application performance?

My laptop screen is 1280*768 and the app runs perfectly when I play it at that size (showing all the frame, the windows toolbar, etc.), but if I play exactly the same movie fullscreen, it goes much slower

thanks in advance

marc

hybrid · Post by **hybrid** » Wed Mar 21, 2007 1:00 pm

Maybe you don't get the same screen depth/stencil buffers etc. on your desktop as you get in fullscreen.

FumarMata · Post by **FumarMata** » Wed Mar 21, 2007 8:25 pm

and is there a way to solve it?

JonLT · Post by **JonLT** » Wed Mar 21, 2007 10:23 pm

I dont really know, but the problem might be vsync.
This can be set when you create an IrrlichtDevice.

hybrid · Post by **hybrid** » Wed Mar 21, 2007 11:00 pm

That might be even a better guess than mine, is your FPS drop always to 60 or 75 FPS?

George · Post by **George** » Thu Mar 22, 2007 3:35 am

If you are running in full screen mode and you have vsync enabled then the maximum frame rate will be the frame rate of your monitor.

To test it, simply change your monitor refresh rate and re-run the application.

CuteAlien · Post by **CuteAlien** » Thu Mar 22, 2007 12:57 pm

With the current implementation the frame rate will actually not be the rate of your monitor but 60 FPS. At least on OpenGL/Windows. Which means that changing the monitor frequency will also make no difference - that value is not used in fullscreen. Not sure if it's different in DirectX.

But disabling vsync should already be enough to find out if this is the problem.

hybrid · Post by **hybrid** » Thu Mar 22, 2007 2:13 pm

This should be correct to fix the vsync to monitor refresh

Code: Select all

        if (wglSwapIntervalEXT)
                wglSwapIntervalEXT(vsync ? 1 : 0);

The one means wait for 1 refresh interval before redrawing.

CuteAlien · Post by **CuteAlien** » Thu Mar 22, 2007 2:24 pm

@hybrid: This is correct (thought there is no reason to restrict vsync to a bool as 2 is also a legal value here). The problem is simply that the monitor refresh rate in fullscreen has nothing to do with the refresh rate which you set in windows. That's something which would have to be changed in CIrrDeviceWin32::switchToFullScreen. To set another frequence one would have to add somthing like that:

Code: Select all

dm.dmDisplayFrequency = frequency;
dm.dmFields |= DM_DISPLAYFREQUENCY;

I don't know why the default is that you get 60Hz, this is just the experience i made.

hybrid · Post by **hybrid** » Thu Mar 22, 2007 3:05 pm

Ok, so that means Irrlicht's OpenGL fullscreen under Windows flickers on CRTs?

CuteAlien · Post by **CuteAlien** » Tue Mar 27, 2007 9:40 pm

I wouldn't say 60HZ is already flickering. It's just not the rate of the monitor which is set in windows. Which i my experience can be somewhat puzzling when you're profiling your game ;-)

vitek · Post by **vitek** » Tue Mar 27, 2007 10:31 pm

The refresh rate value set in the Windows display settings will have no effect on the refresh rate seen in a full screen d3d app. The refresh rate for a full-screen exclusive d3d app is set in the FullScreen_RefreshRateInHz field of the present params. Right now it is getting set to D3DPRESENT_RATE_DEFAULT which allows the runtime to select an appropriate value. I don't believe that setting the dmDisplayFrequency member of the device mode is enough to do it. Maybe I'm wrong...

Travis

CuteAlien · Post by **CuteAlien** » Tue Mar 27, 2007 10:49 pm

Sorry, i can't tell about d3d. I only tested my solution with OpenGL. So i guess that Travis is right and it has do be done somewhat different for d3d.