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Thread: Fill Rate will kill me

  1. #1

    Fill Rate will kill me

    Hello there,

    I'm rendering a textured quad with a simple
    32*32 tex with alpha channel on.
    When this quad covers half the screen, my
    framerate drops to 1 !!!!

    Surely the problem lies wihtin the fillrate,
    but I'd like to know if you don't have a trick to help me with this.

    quadro 4,
    Filtering on GL_NEAREST,
    Blend function GL_SRC_ALPHA, GL_ONE

    Many thanks for any help !!!!


  2. #2
    Senior Member Regular Contributor
    Join Date
    Sep 2002

    Re: Fill Rate will kill me

    Could you post some code first?

  3. #3

    Re: Fill Rate will kill me

    Ok, here's some code.

    // enable blending
    glEnable( GL_BLEND );
    glBlendFunc( GL_SRC_ALPHA, GL_ONE );

    // I use a float pbuffer as a texture

    glBindTexture(GL_TEXTURE_RECTANGLE_NV, m_pbuffer_tex);

    // asimple pass through prog to render the float texture


    // the quad

    // note m_w and m_h are the size of my tex
    // here 32*32

    // x, y , z the pos of the first corner,
    // and w and h the dimension of the tex

    glTexCoord2f(0.0f, 0.0f);
    glVertex3f(_x, _y , _z);
    glTexCoord2f(m_w, 0.0f);
    glTexCoord2f(0.0f, m_h);


    glDisable( GL_BLEND );

    I can post any other info other thing if needed....


  4. #4
    Senior Member Regular Contributor
    Join Date
    Oct 2002
    San Diego, CA, USA

    Re: Fill Rate will kill me

    I see you're using CG. There is a chance that your fragment program is eating up all your fill. Have you tried just simply returning a color value in the fragment program (and doing nothing else) just to make sure your fragment program isnt eating all that fillrate.

    After that, uh, I guess you can try killing the blending but I don't think that's whats hurting your FPS... I honestly think that its the fragment program.

  5. #5

    Re: Fill Rate will kill me

    Ok maybe this is something I should
    have written before....

    I'm using float pbuffer, and as far as the
    quadro 4 I'm using doesn't support this,
    I'm using NV30emulation....

    The fragment program I'm using is nothing
    but a fetch on the texture.

    I was thinking that maybe It could be the problem,
    but when I resize my window the FPS goes better (for a very small window, the fps
    is about 20 fps). That why I suppose
    fillrate has smthg to do with it.

    But on the other hand, maybe the pixel
    shader is called for all the pixels,
    and not only for all the texels (i.e.
    not only 32*32 times, but number_of_pixels
    _in_the_viewport_involved_in_the_tex times)
    Maybe someone knows about this ?

    Thx for all the contributions !


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