Glut Game Mode?

OpenGL OpenGL: Basic Coding
1

So what is Glut Game Mode? I just downloaded the Glut 3 spec and I dont see it in the index. No idea what it is and how to use it. Any ideas?

Thanks in advance!

2

everything you need to know is here:
http://www.fatech.com/tech/opengl/glut/index.php3?1

BTW: it IS in my spec

3

Hey thanks! I got a 30% increase in framerate using it.

4

Wow, another benefit. I have had a texture tearing problem on WinNT4 for several months that I could not explain. It didn’t show up on Win9x or Win2k and NVidia couldn’t tell me what the problem was.

IN GAME MODE THE PROBLEM GOES AWAY … HURRAY!!!

… wish I knew what the problem was tho …

5

vsync is prolly enabled when you’re in fullscreen mode

6

vsync? could you explain that one to me please?

7

Hi,

I don’t actually use glut but reasons for texture tearing that I can think of are… If your desktop bit depth is say 16 bit, GL will use 16bit display in windowed mode. glut game mode will use 32 bit (if requested) and this can sometimes solve texture tearing. If you are running a 16 (or maybe even 24) bit display, put it up to 32 and see what happens.

VSync on the other hand means that GL will not swap buffers until the monitor is ready to refresh. Enabling this will usually slow down frame rates. If you had this enabled and your desktop resolution was high, this would often yield a low refresh rate, hence slower frame rate. Switching to glut game mode (say 800*600) may allow the refresh rate to be higher and thereby give you an effctive frame rate increase.

Hope that makes sense.

8

Hey thanks! My monitor was in 16 bit mode … I switched it and VOILA! No tearing! I just assumed that since I called glutInitDisplayMode(GLUT_RGBA|GLUT_DOUBLE|GLUT_MULTISAMPLE) that a 32 bit display would be used.

BTW: How do you enable/disable VSynch? Any URLS to info on using it? I doubt that I need it but I am a little curious.

Thanks again,
Paul Leopard

9

Oh, and BTW …

Let me see if I understand all of this correctly. Glut default will use the monitor settings I currently have set (size, refresh rate)? Game mode allows me to manually set these parameters?

I have noticed one thing recently that leads me to believe this … When using Glut default my framerate stayed exactly at 60.0 FPS (my monitor was set to 1920x1444:32@60). When I started using game mode (1024x768:32@100) my framerate went up substantially (70-98 FPS).

10

OK,

When you start OpenGL in windowed mode, it will use whatever bit depth you have. glutGameMode sets both resolution and bit depth. Therefore if you to set it to 32 bits, it will use it. Your vertical refresh rate is set by the resolution you are running at. Again, by changing this with glutGameMode you are changing the VSync and therefore your maximum frame rate. Basically all of your assumptions are correct.

I don’t know how to enable/disable VSync in code but it is usually a driver option. This will depend upon your card.

Matt.

11

Thanks for your help Matt.