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Iray render: white shirt too bright

tshaq80_752a50b069tshaq80_752a50b069 Posts: 35
in Daz Studio Discussion

Whenever I render outfits with solid white material, the white parts are rendered way too bright, so it becomes unrealistic. Is there  a way to lower how much light is reflected?

Comments

  • BeeMKayBeeMKay Posts: 7,019
    edited October 2017

    Iray or 3Delight?

    Also, if Iray, are the surfaces converted to Iray, or Iray, or are they 3Delight?

    Post edited by BeeMKay on
  • Richard HaseltineRichard Haseltine Posts: 102,436

    Pure white is unrealistic, so lower the tone a bit. Similarly pure reflections are unrealistic, though that presumably isn't an issue here.

  • MelanieLMelanieL Posts: 7,468

    Also are you rendering through a camera with the headlamp switched off? If not then that might be causing the lighting to blow out whites.

  • PadonePadone Posts: 3,786
    edited October 2017

    Or just go to the Tone Mapping tab and adjust the Exposure Value to your needs. In my opinion having 14 instead of the default 13 gives a more natural exposure in most cases.

    tone-mapping.jpg
    485 x 381 - 59K
    Post edited by Padone on
  • RafmerRafmer Posts: 564
    As stated above, pure white is unrealistic. Never go below (30, 30, 30) RGB when using solid white color.
  • murgatroyd314murgatroyd314 Posts: 1,542

    In the real world, white cotton reflects only about 65% of the light that hits it. Fresh snow reflects around 75%. Polished silver is around 90%.

    In a computer, pure white reflects 100%. Of course this looks unnaturally bright.

  • PadonePadone Posts: 3,786
    edited October 2017

    While it is true that in the real word a 100% "pure" white may not fit the material attributes, it is not true that the burn-out of shining spots is necessarily due to the "pure" white. That is, you can have burn-outs even with "real" whites, the same as  you may not have them with "pure" whites, depending on how the scene is lighted.

    Also, "pure" whites may often be in textures so you may not always be able to change them as you wish. Also, for a Photoshop artist designing textures, the srgb white color is a completely normal color to use. It is just the iray engine that associates it to the real "pure" white color.

    So, using "real" whites certainly helps, but it's not the solution. The solution is to use the exposure parameters to fit the lighting conditions.

    An even better solution is to use a custom transform function from linear colors (used to compute renderings) to srgb colors (used to display the rendering on the monitor).

    That is, PBR engines are using by default the SRGB EOTF function to traslate from linear to srgb. And this is easily prone to burn-outs since this kind of transformation has a limited exposure range to work with. So you have to fit the exposure to the scene choosing your middle grey and having "clipping" in blacks and whites.

    But SRGB EOTF is not obligatory to use. For example in Blender it can be optionally replaced by a "filmic view trasform" function that simulates better the human eyes perception of linear colors in the srgb space. This function expands the exposure range that is translated to srgb and in most cases eliminates the "clipping" of too bright or too dark areas.

    http://colour-science.org/posts/the-importance-of-terminology-and-srgb-uncertainty/

    https://sobotka.github.io/filmic-blender/

     

    EDIT: In iRay you can use the Burn Highlights and Crush Blacks options in the tone mapping panel to customize the transform curve. This gets a similar result of the filmic transform in Blender.

    Post edited by Padone on
  • ben98120000ben98120000 Posts: 469

    tshaq80_752a50b069 said:

    Whenever I render outfits with solid white material, the white parts are rendered way too bright, so it becomes unrealistic. Is there  a way to lower how much light is reflected?

    Render settings tab, under Filtering menu, set nominal luminance between 200 - 400. Luminance is amount of reflected light and 400 is luminance of white paper outside on a bright sunny day. Setting it manually helps with fireflys and render speed since IRay doesnt have to guess anymore.

  • PadonePadone Posts: 3,786
    edited October 2017

    @ben98

    You only need to specify the nominal luminance if you don't use tone mapping. If you use tone mapping this is better left to zero so it is computed from the tone mapping parameters. If you turn off tone mapping then you can set this parameter to give iray a hint. Basically you have two way of working.

    1) Use tone mapping and the iray preview to get the scene lighting you need. When the preview is good enough then render in final quality.

    2) Turn off tone mapping. Set a nominal luminance and use canvases to export to hdr image. Then work in post on the exported image.

     

    https://daz3d.com/forums/discussion/89821/iray-light-source-parameters-vs-tone-mapping-camera-parameters

    Post edited by Padone on
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