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Thread: NV_explicit_multisample specification

  1. #1
    Junior Member Newbie
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    NV_explicit_multisample specification

    Does anyone know where I can find this specification?

    It is part of the 180.10 leaked drivers...

    From EXT_direct_state_access:

    <NV_explicit_multisample: New texture renderbuffer object command
    replaces "Tex" in name with "Texture" and add initial "uint texture"
    parameter>

    void TextureRenderbufferEXT(uint texture, enum target,
    uint renderbuffer);

    <NV_explicit_multisample: New multitexture texture renderbuffer command
    prefixes "Multi" before "Tex" and add an initial "enum texunit"
    parameter (to identify the texture unit)>

    void MultiTexRenderbufferEXT(enum texunit, enum target,
    uint renderbuffer);
    thanks,

    Cub

  2. #2
    Senior Member OpenGL Pro
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    Re: NV_explicit_multisample specification

    Intriguing!

  3. #3
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    Re: NV_explicit_multisample specification


  4. #4
    Senior Member OpenGL Guru
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    Re: NV_explicit_multisample specification

    Well, I can't say that I like that extension. The entire point of a RenderBuffer was that the driver knew that you could not use it as a texture. NV_explicit_multisample allows that.

    It would have made far more sense to allow multisample as part of the internal format of a texture.

  5. #5
    Member Regular Contributor
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    Re: NV_explicit_multisample specification

    Eeek, this looks ugly. It does not support 2D multisample texture arrays,as DX10.0 does. But it contains access to the sample position, which is a DX10.1 feature. Strange blend.

  6. #6
    Senior Member OpenGL Guru
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    Re: NV_explicit_multisample specification

    It does not support 2D multisample texture arrays
    That's because it doesn't support multisample textures. It merely allows you to bind a buffer object to a sampler.

  7. #7
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    Re: NV_explicit_multisample specification

    Don't have the 180 drivers to tinker with it, but the basic usage pattern seems to be something like...

    // Create texture for sampling
    uint rt;
    GenTextures(1, &rt);

    // Create MSAA renderbuffer with desired size, format, samples, etc ...
    uint rb;
    GenRenderbuffers(1, &rb);

    // Render to rb normally ...

    // Now just attach texture to renderbuffer for sampling
    ActiveTexture(...);
    BindTexture(TEXTURE_RENDERBUFFER_NV, rt);
    TexRenderbufferNV(TEXTURE_RENDERBUFFER_NV, rb);

    // Sample in GLSL using texelFetchRenderbuffer((i|u)samplerRenderbuffer sampler, ivec2 coord, int sample)
    // GetActiveUniform returns type of (INT_|UNSIGNED_INT_)SAMPLER_RENDERBUFFER_NV

    Seems to me it's just a temporary binding of a texture and a renderbuffer - temporary mapping of the buffer object
    for the purpose of sampling only (as Korval pointed out).

    For arrays it looks like we'd need something like samplerRenderbufferArray... (I smell an extension here)

  8. #8
    Senior Member OpenGL Guru
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    Re: NV_explicit_multisample specification

    I smell an extension here
    I hope not. This is a crappy way to expose this functionality, and I would hope that the ARB abandons it in favor of something more reasonable.

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