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Thread: shininess

  1. #1
    Junior Member
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    shininess

    Hi all,

    I wonder what is the range of shininess in COLLADA document?
    I'm a bit confused about why there is no certain value in the spec on that..

    Thanks in advance.
    --
    Arman

  2. #2
    Senior Member
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    I tried to get an answer from the guy who currently does most of the work on the Collada material system, but I never heard back from him. I think the range of shininess isn't currently specified in Collada. OpenGL's max shininess is 128 IIRC, so [0, 128] might be a good range to use.

  3. #3
    Senior Member
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    The lighting model equations for the common shaders (e.g <phong> and <blinn>) have been under discussion in the work group and the issue is being tracked in the Khronos Bugzilla.

    I can confirm that prior to COLLADA 1.4 the value was a GL style exponent as Steven said. With the introduction of effects and GLES and GLSL profiles, there has been some movement away from them for the <profile_common> shaders.

  4. #4
    Junior Member
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    Sep 2006
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    Yes there appear to be misunderstanding of blinn between the realtime 3D guys and the DCC guys.
    DCC assumed Blinn-Torrance-Sparrow
    while RT guys assumed Blinn-Phong.

    FXComposer2 attempts to compensate for this by detecting the usage pattern and switching to the appropriate function.

    If shininess 0 to 1 do Blinn-Torrance-Sparrow
    else if shininess >1 do Blinn-Phong

    Blinn-Phong is the typical phong equations using the half vector.
    Blinn-Torrance-Sparrow is quite a bit more complicated.

    I'd suggest installing FXComposer2 and using the effects wizard to generate a Blinn CgFX file then utilizing that code as the Blinn-Torrance-Sparrow portion of your shader.

    Daniel Horowitz
    NVIDIA

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