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Thread: Hdri noise

  1. #1

    Hdri noise

    Hi there!

    I'm doing some animations with HDR lighting, and I can't get ride of noise in reflections in these scene ::

    First picture with HDR lightning, second with default gradient backdrop, otherwise, same settings.

    Click image for larger version. 

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    HDR is giving some nice reflections, but in some areas, it's really grainy (very annoying in animations)

    Red Spot > The noise appears on the dark metal, there is glass in front of it, and noise disappear if I use 100% transparency on glass, that may be a clue? (distance between metal and glass is 13mm)
    Green Spot > Mystery to me ... just a glass (6 quad polys) with 20% reflection and 40% transparency, no node or shader

    I have also join a screen of my setings if it can help? (I have tried 20 antialiasing, but result is the same)

    Click image for larger version. 

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  2. #2
    Super Member Snosrap's Avatar
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    Aug 2004
    Ohio, USA
    Does gaussian HDR filtering correct it?

  3. #3
    usually you exclude the glass from the GI in the object properties render settings tab for this sort of thing (at least I do), also the at least as far as SIBL's version of this as stated above the GI HDR is usually very blurred to help counter this and a separate sharp HDR is used for reflection. also I usually have a higher light sample than one, I find every thing is specked if I don't

  4. #4
    Snosrap, no it doesn't, but I usually go to that directly (despite that sometimes, it's giving me some funky alpha layer)

    Gerry, thankx for the exclude from GI tips! Never do that. It doesn't fix the issue here, but it's good to know.

    Indeed, I had this central glass door, and behind the camera, facing the central door, another glass surface + the windows in background. I had to delete reflections on background windows + "behind the camera glass" to avoid noise ...

    Click image for larger version. 

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    So I guess, it's kind of fixed, but I didn't get the problem :/

  5. #5
    Could ray recursion be the issue? I doubt it but you seemed to have everything else covered. I like the rug, what was the surface type for the fibers? Also are you adding more IES light for the double lamps by the door?

  6. #6
    I tried to push ray recursion to 20 but no results ... I think I would have to create a simple scene with multiple glass and hdri to find the issue. The rug is geometry (I think it's a model from 3Dsky, they have pretty awesome models once you convert them). About IES I just have two light by lamps (up and down) ... but 4 but lamps would be more logical your right

  7. #7
    is it not the case that radiosity does not like too much specular on a given surface (if any at all), this is why glass is such a problem as it usually has a default specular value of 100%, why not try unchecking affect specular on all your lights in the lights property pane see if it helpsl, also gradient set to incident angle to limit reflections on glass might help.

  8. #8
    Thank you gerry! Well I never use specular in my render for architecture. I always try to have a coherent environment so that reflections replace specularity. This is changing actually, as I just realize that most of people I made images for doesn't see the difference (and well, setuping realistic reflections or just cheked 100% specular are two very different paths, regarding the time it take ^^). But I'm glad Lightwave have that reflection+specularity option. So no specularity in that scene anyway. And I always use gradient set to incident angle (or sometimes fast fresnel shader, it's fast and give nice resulats). I wanted to have nice reflection on surfaces parallel at the camera (don't know if my english is good here ^^' ) ... so for me here, it's a rendering issue I could solve with setuping render (I spend hours on it) but, well, it's Lightwave, so a few tips and tricks could always been found to fake the results :P


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