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Thread: GL_POINT_SMOOTH (circles vs squares)

  1. #1
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    GL_POINT_SMOOTH (circles vs squares)

    well, i see glEnable(GL_POINT_SMOOTH) is implementation-dependent... is there a way to force the 'rounding' of a point even if it's not supported by the hardware?

  2. #2
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    Re: GL_POINT_SMOOTH (circles vs squares)

    hey! I suppose everybody but me knows the answer...

  3. #3
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    Re: GL_POINT_SMOOTH (circles vs squares)

    I dont quite understand. glEnable(GL_POINT_SMOOTH) rounds points.

  4. #4
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    Re: GL_POINT_SMOOTH (circles vs squares)

    well, not on an ATI-rage equipped i-mac, not on a windows PC with a matrox G400, G450, G 550, not on an ATIradeon7500 powered mac G4 ...
    on such machines the point won't be antialiased. and will be rendered just as a square (you'll notice it better if you set glPointSize(n) with n bigger than 1, i.e. 5)... i tested my app on a PC with an ATIradeon7500 and the 'rounded'points could even grow screen-wide. just a matter of drivers?
    thanx for answering

  5. #5
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    Re: GL_POINT_SMOOTH (circles vs squares)

    It's been awhile since I tried to enable GL_POINT_SMOOTH in an app, but if I remember correctly, you also had to enable blending.

    Edit: Just put together a quick test app and I guess I didn't have to enable blending for it to work. I'm on my work computer, which just uses the default software implementation from Microsoft.

    [This message has been edited by Deiussum (edited 07-17-2002).]
    Deiussum
    Software Engineer and OpenGL enthusiast

  6. #6
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    Re: GL_POINT_SMOOTH (circles vs squares)

    for what i know, you ALWAYS HAVE to glEnable(GL_BLEND) to obtain antialiasing... the software renderers (SGI's for Windows, Microsoft's and Apple's) correctly implement point antialiasing.
    the trouble starts when using hardware-acceleration. it seems to me that not all hw-accelerated renderers support GL_POINT_SMOOTH. in fact, the only one i found out to be correctly implementing GL_POINT_SMOOTH is ATI's RADEON VE SDR x86/SSE2 win release. of course, there may be others...
    isn't it is curious that a sw-renderer does a better job than a hw-renderer?
    maybe we got to use some proprietary extensions instead of GL_POINT_SMOOTH (like in example GL_VENDOR_POINT_SMOOTH that of course doesn't exist)? and if yes, which one? anyone got some useful hints?

  7. #7
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    Re: GL_POINT_SMOOTH (circles vs squares)

    Have you tried the POINT_PARAMETER extension?
    Worked for me, but then again it was on a ATIradeon7500 which you say worked anyway.

  8. #8
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    Re: GL_POINT_SMOOTH (circles vs squares)

    no, i didn't try this extension.
    but unless i misunderstood the extension's techspec i think it has nothing to do with antialiasing the point primitive. for what i know it affects just the point size and in certain cases the point opacity according to the eye distance... lemme know if i'm wrong
    thanx

    [This message has been edited by zobel (edited 07-19-2002).]

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