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Thread: Multisampling Problem

  1. #1
    Junior Member Newbie
    Join Date
    Sep 2004

    Multisampling Problem

    Hi everybody,

    I'm fairly new to OpenGL and I've been working through the redbook and trying out all of the sample code. I've gotten up to using multisampling to get full-scene antialiasing, but I'm having some problems.

    I'm working with the multisamp.c example file which uses GLUT, and I'm compiling it with VS.NET so I've had to include glext.h as well. It queries GL_SAMPLE_BUFFERS_ARB and GL_SAMPLES_ARB first and spits out those values and then displays two pinwheel patterns, one with multisampling and one without. The problem is that it says that both values are 0 and there is no visible difference between the two patterns. I've got a GeForce3 card which I'm pretty sure supports multisampling. I've been able to turn FSAA on through the display control panel, and then it reports the buffers as 1 and the samples as 4 and there is a visible difference, but if I leave the driver setting on Application Controlled, it doesn't work.

    I'm using GLUT to request a window with the GLUT_MULTISAMPLE bit in there, and I'm taking the example file exactly as it is and just including glext.h at the top.

    Can anyone tell me what I'm doing wrong? I know the there is a multisampling tutorial on NeHe's site, but it doesn't use GLUT and I don't think I should have to make it windows-specific.

    Please let me know if anyone can help me out or point me in the right direction.



  2. #2
    Senior Member Frequent Contributor
    Join Date
    May 2001

    Re: Multisampling Problem

    I've not tried with GLUT, but the first thing I'd do is creating the framebuffer with the GLUT_MULTISAMPLE bit. Do you use it ?

  3. #3
    Super Moderator OpenGL Guru imported_dorbie's Avatar
    Join Date
    Jul 2000
    Bay Area, CA, USA

    Re: Multisampling Problem

    It could be your display settings, you can override the software there.

    Check the Display Properties->Settings->Advanced->....
    Now in there you may see your graphics card name, you may then see performance & Quality. It depends on your card/drivers I think.

    You might just see OpenGL in there as a section, but poke around you're in the right place.

    Once you find the Anti-Aliasing control you'll see that it lets you set a few basic settings, either application-controlled (which you should have for your testing), or anything from no samples to 8 samples with and without quincunx.

    Again this depends on your hardware.

  4. #4
    Junior Member Newbie
    Join Date
    Sep 2004

    Re: Multisampling Problem

    Hey Guys,

    Thanks for your responses.

    I am passing GLUT_MULTISAMPLE into the glutInitDisplayMode function, so I think the window should support it. I also have blending, depth testing, and multisampling turned on with glEnable.

    I'm able to get multisampling to work if I turn on antialiasing in the display properties, but if I just leave it on application controlled, it doesn't seem to work. I'm sure if it's set to "Application Controlled" that I should be able to control it somehow without having to mess with display properties.


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