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Thread: Pipeline Newsletter Volume 4

  1. #141
    Junior Member Regular Contributor
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    Re: Pipeline Newsletter Volume 4

    Vertex texturing is also slow on the 7xxx cards, the latency of the texture fetch isn't hidden and it's pretty difficult to find enough work to do after the texture fetch to hide it yourself...G80 cards texture at full speed in all geometry stages, I believe.

  2. #142
    Member Regular Contributor
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    Re: Pipeline Newsletter Volume 4

    Any insights on these vertex texturing issues on AMD GPU's ?

  3. #143
    Senior Member OpenGL Guru
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    Mar 2001
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    3,576

    Re: Pipeline Newsletter Volume 4

    Any insights on these vertex texturing issues on AMD GPU's ?
    As I recall, ATi cards didn't support vertex texturing before the R600. And the R600, like the G80, uses a unified shader architecture, so the same texture units are used in all stages. As such, I imagine they perform reasonably well.

    Of course, part of the NV40 problem is that you can only vertex texture from floating-point textures, which hurts performance-wise.

  4. #144
    Member Regular Contributor
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    Re: Pipeline Newsletter Volume 4

    Just to confirm; no ATI card before the R600 can do Vertex texture fetches.

    As I recall the reasoning was it would be too slow to be useful/worth while doing for the transistor cost as such they didn't impliment it. (This became the stuff of many flame wars in certain quaters over the lack of VTF vs SM3.0 spec...)

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