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Thread: help with shadow exclude

  1. #1
    Newbie Member
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    help with shadow exclude

    can someone help me understand how you use shadow exclude? i want to get rid of a light hitting the ground but i want to keep the shadow it produces.
    any help will be great. thanks

  2. #2
    Registered User
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    I don't think you can exclude a object from a light and still have it receive shadows from that light. The workaround is to set the ground up as a shadow only alpha and comp the shadow in later.

  3. #3
    Newbie Member
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    Apr 2006
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    california
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    i am very new to lightwave so i dont quite understand everything but in the contents for light exclusion it says,

    "If for some reason you need the excluded lights to continue to cast shadows, deactivate the Shadow Exclusion option. When this global setting is not activated, all lights will cast shadows even if they are excluded."

    my scene is inside a sphere with an image mapped to it and a gradient on it in the luminosity settings to light the scene up like a hdri and it is working well,

    but my problem is i have a sun in the image and i want it to cast hard shadows on my objects with out it lighting up the ground anymore.

    i will try to make a shadow only alpha of the ground like you suggested. hopefully that is easier to try to figure out. thanks

  4. #4
    You could try Jeremy's script called Shadow Lights:
    http://jeremy.lwidof.net/lscript/

    But the reason you won't get sharp shadows from an HDR is that the part of the image that represents the sun is not far enough away from your scene. You get sharp shadows from the sun in real life because the sun is so far away that the only light rays that reach the earth are all parallel. In your HDR, every pixel is basically acting like a point light, casting lght in all directions, giving you soft shadows everywhere.

    All you need to do is add a Distant light and put it where you see the sun in the HDR, which will also cast a more accurate sunlight on your subjects.
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