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Thread: Clueless with nodes... Issues with shadows?

  1. #1
    Uber Noob IgnusFast's Avatar
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    Clueless with nodes... Issues with shadows?

    I'm using this lovely nodal surface for ice (I'd give credit, but this was an old internet find and I can't locate it any more), but it *barely* casts shadows, which is extremely unrealistic. Any ideas how to fix/enhance the shadows?
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  2. #2
    Super Member XswampyX's Avatar
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    Copy your ice object into a new layer in modeler. Give it a new Ice_Shadow surface and then in layout make it unseen by camera etc. Then adjust the Ice_Shadow surface to give you a good shadow.



    Not brilliant I know, but it's late.

  3. #3
    it's a manhole cover ↓ JoePoe's Avatar
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    Good idea swampy.

    Can you post an image of what you are seeing?
    This type of transparent/reflective surface relies so heavily on everything else in the scene.

    Simple stuff first (sorry):
    Ray trace shadows, reflections, retractions all on?
    Is there something in the environment to make this type of surface "sing"?

    Try turning on caustics.
    Below:
    1) out of the box srf one area light (hdri environment).
    2) same but with Caustics on.
    3) Caustics with a little radiosity to cut it back some.
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  4. #4
    Uber Noob IgnusFast's Avatar
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    Holy crap! Whoda thunk that caustics could make that dramatic a change? I thought they just caused light focal points, not the reverse... More of a general volumetric effect? I had actually played around with caustics, but I have 28 lights in the scene, and it just took FOREVER (several hours for a single render, almost like being back on my A4000!), so I never let one complete.

    I'll play around with these ideas - Swampy's use of the shadow form looks decent in VPR - trying out a full render now. Will take a while.

    Here's a render of the original scene...
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  5. #5
    it's a manhole cover ↓ JoePoe's Avatar
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    Certainly Swampy's will get you there!!

    And I'm sure you realize that caustics can be utilized on a per light basis . You may only need one. But I DOES still take time.

    But the scene (which is pretty cool btw ) seems pretty well light all around with a lot of cross shadows from different lights (Yes?). Not sure where you are expecting the heavier shadow from the ice block. Right side? Again you might only need one. Swampy's will give you ALL the cross shadows, if that's what you want, unless you start "excluding".
    Last edited by JoePoe; 07-08-2013 at 08:40 PM.
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  6. #6
    Uber Noob IgnusFast's Avatar
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    The shadow object does work, but it has the additional side-effect of really darkening up the inside of the ice block. So actually did the use of caustics, so I think I'm either going to have to go a different direction, or do something really creative with it. I'll post shots of both.

    I even did one crazy render where I flipped all the shadow blocks' polys; that came out interesting, in that the ice block was awesome looking, but the minion and stuff embedded looks goofy.

    I wish there was a way to exclude objects from shadows - that would really be handy! So instead of shadow *catcher*, there would be a shadow *caster* node that could exclude objects. Or maybe that's just silly.

  7. #7
    Super Member XswampyX's Avatar
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    You did tick unseen by rays, unseen by radiosity, self shadow and receive shadow on the shadow object properties as in the screen shot I posted?

    Just checking.

  8. #8
    Uber Noob IgnusFast's Avatar
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    I did indeed. I've attached a test scene... well, basically the same scene but jury-rigged. It's set up to render a frame each for the nodal surface, the nodal with shadow object, then a non-nodal version just for kicks.
    Attached Files Attached Files

  9. #9
    Uber Noob IgnusFast's Avatar
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    Wow, that is strange. I just started re-rendering this exact scene, and the difference between the first two shots is much more in-line with what I expected to see... Odd!!

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