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Thread: Shadows through glass

  1. #1
    Curmudgeon in Training Ma3rk's Avatar
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    Shadows through glass

    Need some direction on how to solve the rendering issue shown below. At first I simply couldn't tell what I was really seeing. So, I rotated the door away from the wall a few degrees & that showed that the problem is the "shadowing" on the wall & not the glass panes themselves as I first thought.

    Initially, the entire area of soft, bluish light, and just that area, was very grainy. That's coming from the windows on the landing, which is an HDR eviro light. I increased the lights samples which cleaned up the wall that the light is hitting directly, but didn't for what's going through the panes of glass to the wall; just made that more evident.

    The walls are PBSDF, but no textures, just simple white & 25% rough, raytrace only & glossy reflects off.


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    Suggestions?
    "Never be a cat in a cartoon. Never." Chief Wiggum

  2. #2
    Is "Opaque" checked on the surface panel? That determines if glass will create a shadow or not. Otherwise I think you should experiment with higher Reflection and Refraction Recursion Limits. Also try and maintain 2,4,6,8,12,16,24,32,48,64,92,128,256,512,1024 etc. etc. - you get the point - settings. Also Diffuse Bounces (almost) never need to be greater than 2 and certainly not in this scenario. Your interpolated settings are way out of wack and should follow the basic rule I've described above. Brute Force Rays have no effect as soon as you check Interpolated.
    Also the lights in 2018,19 are just amazing and I'm in the middle of a project where I think I'm relegating GI to the "do not use for interiors bin" - something that maybe you should consider too. My initial work on this is looking promising. Good luck!
    Tim Parsons
    Technical Designer
    Sauder Woodworking Co.

    http://www.sauder.com

  3. #3
    Curmudgeon in Training Ma3rk's Avatar
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    Hey Tim,

    I tested both with & w/o on the Opaque and it didn't help. I usually use a powers of two progression or pi.

    Forgot to post the Glass settings before:

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    I leave the Brute Force set to 2 only for when I toggle Interp On/Off as it still affects VPR.

    I'll have to dig back & find your recommends (unless you care to post the link), but these are largely based on RH's vids & incremental testing. GI of course is primarily FOR interiors, but I know what you mean.

    I like to lay in the "Practicals" first then go back & fill as needed later. I then toggle GI On/Off as a check. Eventually you get to a point where you don't/shouldn't need it.

    I'll have to review the Diffuse Bounces topic again. I'll make some tests with higher Reflection and Refraction Recursion Limits. I did look at the Shadow buffer btw & it's quite grainy in those areas.

    Oh, and thanks a ton for mentioning the ef Item Focus tool in another thread that I couldn't find again. Imagine trying to place door pivots & fixture lights in this model with basement, two floors and an attic w/o it? I have those as separate layers, but even so.

    Haven't even touched the basement yet.

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    "Never be a cat in a cartoon. Never." Chief Wiggum

  4. #4
    Looks like your on the right track and your workflow seems sound. Didn't want to sound condescending on the settings, but I see the weirdest stuff posted sometimes and I am glad to hear you typically use those. One last thing - isn't the IOR of glass 1.52?
    Tim Parsons
    Technical Designer
    Sauder Woodworking Co.

    http://www.sauder.com

  5. #5
    Curmudgeon in Training Ma3rk's Avatar
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    Nah, you didn't come off that way at all. I've watched some of the RH vid's multiple times but the key points are scattered about, so is awkward trying to recheck some things. He should put out a "Key Points to Start With" synopsis.

    I just had the IOR turned down to test.

    There's a chandelier in one of the rooms with leaded glass crystals that I'm avoiding for the moment.
    "Never be a cat in a cartoon. Never." Chief Wiggum

  6. #6
    Curmudgeon in Training Ma3rk's Avatar
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    I didn't feel like doing battle with the Dielectric material so made those door panes Standard with typical glass settings. Need to work on corners now.

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    "Never be a cat in a cartoon. Never." Chief Wiggum

  7. #7
    Yep the glass looks much better. Good luck with the splotchies.
    Tim Parsons
    Technical Designer
    Sauder Woodworking Co.

    http://www.sauder.com

  8. #8
    Not so newbie member lardbros's Avatar
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    Hi there,

    The graininess through the glass is your refraction samples. Probably need them up to 32 or higher I imagine, that'll smooth them out!
    LairdSquared | 3D Design & Animation

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  9. #9
    Curmudgeon in Training Ma3rk's Avatar
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    Quote Originally Posted by lardbros View Post
    Hi there,

    The graininess through the glass is your refraction samples. Probably need them up to 32 or higher I imagine, that'll smooth them out!
    I'll experiment with that.
    "Never be a cat in a cartoon. Never." Chief Wiggum

  10. #10
    Not so newbie member lardbros's Avatar
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    Quote Originally Posted by Ma3rk View Post
    I'll experiment with that.
    Ooh, and before I forget... if your roughness is at 0% with the Dielectric (or Standard shader... although I wouldn't recommend the Standard one really) you wouldn't need to up your refraction samples.

    Just tested this now:

    Turns out, it's only the Dielectric that causes your issue, which isn't what I expected. You can also use the PBSDF material and put your transparency up to 100% and you get nice glass too.
    It may actually be a bug or something with the dielectric shader, because it seems to require that you up your refraction samples to get the clean render behind the glass, even with 0% roughness.
    Last edited by lardbros; 09-16-2019 at 09:55 AM.
    LairdSquared | 3D Design & Animation

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  11. #11
    Member jgutwin's Avatar
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    I have had similar looking splotches which I finally traced down to a small intersection between each light and their lamp. Try a rendering with the lamp geometry hidden as a quick test.
    John Gutwin
    Pepperchrome

  12. #12
    Curmudgeon in Training Ma3rk's Avatar
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    Quote Originally Posted by lardbros View Post
    Ooh, and before I forget... if your roughness is at 0% with the Dielectric (or Standard shader... although I wouldn't recommend the Standard one really) you wouldn't need to up your refraction samples.

    Just tested this now:

    Turns out, it's only the Dielectric that causes your issue, which isn't what I expected. You can also use the PBSDF material and put your transparency up to 100% and you get nice glass too.
    It may actually be a bug or something with the dielectric shader, because it seems to require that you up your refraction samples to get the clean render behind the glass, even with 0% roughness.
    Hey, thanks for testing that. I was seeing this before the 2019.13 update so it's not new. I ended up doing essentially what you suggested. I set the roughness below 1 but not zero.
    Last edited by Ma3rk; 09-16-2019 at 11:00 AM.
    "Never be a cat in a cartoon. Never." Chief Wiggum

  13. #13
    Curmudgeon in Training Ma3rk's Avatar
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    Quote Originally Posted by jgutwin View Post
    I have had similar looking splotches which I finally traced down to a small intersection between each light and their lamp. Try a rendering with the lamp geometry hidden as a quick test.

    I'll look but suspect it's a GI thing.

    I started with point lights but didn't like the look so went with spheres instead. I haven't surfaced anything yet; the model had some basic stuff initially, but I set most of the large expanse surfs like walls & ceilings to a very plain white surface until I've the lighting in. Glass & such I start with one of the presets usually. So all the Overheads & Sconces have actual geometry. I'm not using Caustics & some spots could be from refraction but not all.
    "Never be a cat in a cartoon. Never." Chief Wiggum

  14. #14
    Member jgutwin's Avatar
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    Yes, In my case it was a GI thing also but it greatly improved when the lights did not intersect geometry.
    John Gutwin
    Pepperchrome

  15. #15
    Not so newbie member lardbros's Avatar
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    I've reported it as a bug, not sure it's right... so we'll see i guess
    LairdSquared | 3D Design & Animation

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