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Thread: floating point texture storage requirements

  1. #1
    Member Contributor
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    floating point texture storage requirements

    I believe 8/16 bit RGB images are aligned on 32/64 bit boundries (ie you get an alpha if you want one or not).

    Does the same apply to floating point (RGB) textures? Do these occupy 96 or 128 bits of vidmem?

    Regards
    Mark

  2. #2
    Senior Member OpenGL Pro Zengar's Avatar
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    Re: floating point texture storage requirements

    I don't think you will ever find out... It will most probably depend on the card. But I guess that the alignment is 32-bit for Nvidia hardware (and probably for ATi too).

  3. #3
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    Re: floating point texture storage requirements

    128, almost certainly. GPUs supporting true 3-channel textures are mythical beasts.

  4. #4
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    Re: floating point texture storage requirements

    Thanks chaps... I also found this.

    http://http.download.nvidia.com/deve...re_formats.pdf

    I didn't really expect 96 bits, but it would have been nice!

  5. #5
    Senior Member Regular Contributor PaladinOfKaos's Avatar
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    Re: floating point texture storage requirements

    The vector hardware in the GPU (as well as the CPU if you do any real work there) is based around 4 components. Converting from a 3-component memory format to a 4-component register format is just too much work - it's easier and faster to just leave a dummy channel.

    The reason there is native support for 1- and 2-channel textures is that they can be packed into a 4-channel texture, that is

    Code :
    {r}{g}{b}{a} // RGBA
    {r}{r}{r}{r} // R
    {l}{a}{l}{a} // LA
    {r}{g}{b}{*} // RGB
    The unofficial community-lead OpenGL SDK is in development! http://glsdk.sourceforge.net

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