Blocky Shadows from HDRI
MelissaGT
Posts: 2,611
Hello all! I was hoping I could get some help on why shadows are showing up blocky (mostly on her sleeves) from this particular HDRI. If I change the HDRI, I don't have a problem...and this specific one has given me issues ever since I moved to 4.15. I've used it on a ton of my scenes and I never had this issue til recently. I don't get it. It's from Skies of Gaia 2, so it's high-end, and like I said, all the other HDRI seem fine. It's driving me crazy because THIS specific one is perfect for the scene I'm doing and I really don't want to have to find something else. I've upped the SubD on the shirt to 2, so that's not it. The environment lighting is set to 8192px. Burn highlights/shadows doesn't help. Any thoughts?
I didn't let the render run all the way through in my example, but the blocky shadows won't clear even with time.
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Comments
Did you try turning the gloss down on the shirt?
I tried a completely different shader and it's still giving the same blocky shadows, so it's not the shirt. If I swap the HDRI out to a different one in the same pack, it's also fixed.
Turn the brightness down on the HDRI?
That would make the scene too dark. It's set at default 1. And even so, with changing it, the problem still persists.
Try reducing Burn Highlights in Tone Mapping. See if turning on or off burn per component makes a difference.
No difference :(
Is there a normal map on the shirt? If so, you could try messing with the settings or disable it completely to see if that helps.
Boy this is an anoying issue with some clothes. It's due to both lighting and your texture set-up. I see it mostly with HDRIs.
One the left is the default tectures/shaders, on the right is with the changes I had to make to get rid of the effect. I think I needed to apply the UberSurface base and work from there but it was a long time ago so I'm not sure.
Yes, but the problem persisted when I tried a different shader that overwrote the normal that comes with the shirt.
You did all the usual stuff. To be honest, I've not had great success with the Skies of Gaia generally. Cake'n'Bob, Orestes, Dreamlight and MEC4D all seem to work fine. I don't know what it is.
The blockiness goes away when I turn on spectral rendering...which now screws with all the skin settings. And the best part is this is a promo so I can't/shouldn't really mess with the character's skin and it looks ooofta under spectral rendering.
Here's where your problems would disappear if you started using canvases! One pass for everything that works with one setting, and another pass for everything that works with the other setting. Minor adjustments in Ps or whatever, and you move on.
Seriously, you'll love the flexibility, and wonder why you waited so long. Render files get way bigger, but you can ditch them after you've exported your final image.
The render I did above showing the affect was with Cake'n'Bob's beach HDRI, so lighting could be seen as coming secondary to material set-up, althought it oviously plays a part in the overall issue.
The quickest fix for me was to strip out the cloth material settings and compile another in Iray preview mode until the undesired affect goes away. Don't mess with your render setting as you'll just be adding a whole new set of problems onto your current one.... Occam's razor.
Long shot, only if you're desperate... I haven't had this particular shadow issue, but others related to HDRIs from hdrihaven. I noticed that extreme (realistic?) dynamic range can cause trouble. You can't see it on your monitor, but on some HDRIs the core of the sun is MUCH brighter than the whole "sun disc". This means that most of the light comes from a very small area, and that seems to not play well with iRay.
I've fixed a few maps by making the sun core darker, and the whole sun disc brighter to compensate. No idea if this would help with your cloth shadows.
Finally someone has the same issue, and it's only for exactly one HDRI from this pack, right. I think you refer to this one? https://www.daz3d.com/skies-of-gaia-volume-2--40-8k-hdris-for-iray ;
Here, I get this for the very first HDRI image in this pack, all others work perfectly fine, so I am pretty sure that this is a product-related issue. If you look below, the PA has used the same lighting with mountains in the scenery, this one doesn't have the effect for me and if I can, I normally switch to this one. I agree, the first one has a beautiful lighting, but I can hardly use it and I might submit a ticket here.
I can confirm this. I have the same issue with really high dynamic range images in 4.15 (not sure about older versions).
Spectral rendering is a more accurate rendering mode, you need to fine-tune the skin shaders in order to fit it, really, spectral rendering mode should be the default setting as it's much more realistic and less waxy!
This isn't an issue with any DS version. I've seen it well before the current version. What surprises me is that some people try to fix it by the most convoluted and, forgive me, stupid means possible.
The problem is with the cloth mat set-up and can be fixed with that alone. The HDRI is just a side-issue of no real revivance. Start up your scene in Iray prevew mode and work with the nodes on the cloth until the problem goes away.
Leave the damn lighting alone, it's not the real problem. Just because you have a hammer not everthing has to look like a nail. I fixed the issue in 5 minutes with a minumum of nous. Don't overblow a simple problem that is easily fixed with a modicum of effort and comon sense.
Turn down the environment lighting resolution. If the HDRI has a fine, sharp, light source you'll just exacerbate the issue with a very high ELR. There's generally not a lot of reasons to deviate from the default - it doesn't affect the resolution of the HDRI as a backdrop, just the resolution used in the lighting calculation.
Other things to try:
Yes! This is exactly it! I tried swapping to the one with the mountains, but that unfortunately changed the lighting just enough for me to not want to use that one. All the other HDRI in that pack are fine. There's something about this specific one that is just odd.
Here is an example with "sunny_vondelpark_16k.hdr" from hdrihaven. With this one I can reproduce the issue every time. And it seems nothing on the ubershader side can solve it (only setting backscattering to a high value helps but that of course is not suitable in most cases). The same scene with a less intense hdr is ok. The waveforms show the range difference.
Is there a way to fix the HDRI by resaving in Photoshop?
Now this IS interesting.
I came across the same problem in 2019 with this rendo image: https://www.renderosity.com/rr/mod/gallery/not-a-ruin-yet-/2877548/ and put it down to both my inexperience & the lack of a displacement map on the OOT Megawardrobe camisole top. Maybe I had the wrong cause identified.
I may go & re-visit that image sometime.
Regards,
Richard
I have finished the image, however I need to wait for the promo album to be released and then I will post my finished piece along with what I did to fix! (Well, it wasn't exactly a fix...more like a workaround...)
You have posed many questions. Many people have tried to help. And now you withhold information on how you "fixed" it.
I can understand holding off on posting a future promo image, but not holding off on posting the problem solution.
It's not a solution. I literally had to render the image twice...once with spectral rendering and once without just to get the correct skin. I was holding off because that explanation makes more sense when there's an image to reference.
It seems as though my original attachment has been removed (not sure why). In my case, I upped the SubD to 2 on the clothing in question and it made no difference. And even with turning spectral rendering on, I still ended up with some jaggies in the final image that needed to be cleaned up in post.
Sorry, trying out several ways to edit hdrs at the moment - this opened another can of worms. So far no real luck.
What I can say already is that any hdr with high contrast triggeres the issue. E.g. as soon as there is a bright sun included and it was not severly clipped by the creator iray shows the shadow terminator issue.
I am trying to find a way to tune down the super whites. But so far it always ends that either the contrast of the hdr gets to low (render does not look like harsh sun anymore) or the blocky shadows appear.
Do you happen to have the Skies of Gaia 2 pack by DimensionTheory? https://www.daz3d.com/skies-of-gaia-volume-2--40-8k-hdris-for-iray
These are more "artistic" rather than real-word lighting and I'd love if your or anybody else could take a look at them specifically. The only HDRI in the pack that has given me grief is the first one. And if I use the version that has the mountains in the background (the sky is the same), then the issue goes away.