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Thread: Technical reason why polygon stipple is slow on ATI?

  1. #1
    Junior Member Newbie
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    May 2002
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    Technical reason why polygon stipple is slow on ATI?

    Is there a technical reason why GL_POLYGON_STIPPLE doesn't slow down rendering at all on my geforceFX at home, but at school on my ATI FireGL X1 it makes rendering very very slow?

    I want polygon dithering

  2. #2
    Guest

    Re: Technical reason why polygon stipple is slow on ATI?

    do you want dithering or stippling? two different things.

    i any case, it could be any number of things. it could be some combination of states thats forcing a software path, and so on.

    try to be more specific about the conditions, post code, etc.

  3. #3
    Junior Member Newbie
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    Re: Technical reason why polygon stipple is slow on ATI?

    Ok, I thought that dithering was when a polygon is displayed like this:

    http://pages.cpsc.ucalgary.ca/~cherlin/glboard.png

    But either way that is the effect I want. Perhaps you could give me the correct name of this as well?

    As for code, well, It is just like:

    glEnable(GL_POLYGON_STIPPLE);
    (render some models via GL_TRIANGLE_STRIP)
    glDisable(GL_POLYGON_STIPPLE)
    (render some models via GL_TRIANGLE_STRIP)
    glEnable(GL_POLYGON_STIPPLE);
    (render some models via GL_TRIANGLE_STRIP)
    etc

    However, I have vertex and fragment shaders running using during all of this

  4. #4
    Guest

    Re: Technical reason why polygon stipple is slow on ATI?

    Joseph, i dont know what to tell you about the speed hit. probably a software path on that fire gl, dunno, not familiar with that card.

    dithering is briefly discussed in the redbook (chapter 5, skip down a bit):
    http://www.parallab.uib.no/SGI_books...html/ch05.html

    basically it allows for an increase in percieved color resolution.

  5. #5
    Guest

    Re: Technical reason why polygon stipple is slow on ATI?

    oh, as for the name thing, im thinking "contour", but im not sure what youre after.

  6. #6
    Junior Member Newbie
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    Re: Technical reason why polygon stipple is slow on ATI?

    Doubt it is a software path since the shader still works and it is not possible that the shader is being done in software.

    --Joseph

  7. #7
    Guest

    Re: Technical reason why polygon stipple is slow on ATI?

    vp/fp can be emulated in software. just try disabling dithering -- see what happens. try diabling stenciling -- see what happens. compare card specs. how many instructions do your shaders have? what's the maximum number on that card? glGet* is your friend. experiment!

    heres a site that gives all kinds of info on various cards: www.delphi3d.com

    hope this helps!


  8. #8
    Guest

    Re: Technical reason why polygon stipple is slow on ATI?

    oooooops! its www.delphi3d.net

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