Author Topic: Wrong smoothing with displacement  (Read 989 times)

2020-05-07, 09:20:24

rdm

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Hello, I have an annoying problem with displacement. I'm not really sure if it's bug or my unawareness.

When I try to use displacement map on my low poly model exported from Zbrush, I can see poligon edges. It looks like wrong smoothing groups. Even when I use pure black map, it gives me the same results. Checkout screenshots.

I tried resmoothing everything, before and after displacement. I tried different subdividing methods. Nothing works.

I might be missing some magic button, but can't figure it out.
3DS Max 2020, Corona 5 hotfix 2

Thank you,
Bartek

2020-05-07, 09:45:08
Reply #1

romullus

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I had very similar issue with displacement from Zbrush some years ago. It turned out that low-poly model came out from Zbrush with inverted UVs. Add Unwrap modifier on the head object and check its UVs, you may see that every edge is split, check individual vertices and see if every single polygon UV is flipped. I can't remember how i solved this issue, but i had to google for solution. I think the model needs to be re-exported from ZB with different settings.
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2020-05-07, 11:24:52
Reply #2

rdm

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I'm not really sure if it's UV related. In attachment you can see that everything looks fine. Even when with simple box mapping, the issue is in the same places. In exporting options from zbrush I believe i tried everything. For me it looks like Corona doesn't smooth model with displacement map properly. Using standard 3DS Max displace modifier works fine with this model and map (but with need to very high model subdivide which is impractical).

In old displacement method (not 2.5D) it looks much worser. I mean, the smoothing is even more wrong, and can't achieve good shading direction at all.

2020-05-07, 15:35:36
Reply #3

romullus

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Hmm, UVs seems fine. I'm a bit puzzled why you're applying displacement on a model with various levels of subdivision? I'm sure you know that displacement should be applied at the same subdivision level at which displacement map was baked. But of course that still shouldn't lead to such extreme artifacts. Although displacement works fine in Corona, it could be that there's unnoticed isue with 32bit maps. What Corona version you are using? It's also would be very useful if you could upload troublesome assets to private Corona's uploader for support team to investigate the issue.

https://corona-renderer.com/upload
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2020-05-07, 17:09:59
Reply #4

rdm

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Okay, there was no popup at the end of upload, but I hope it uplouded fine. Model was exported at SubDiv 2 from zbrush, Displacement was baked from SubDiv 2 in Zbrush. Full SubDiv in Zbrush is 8. In Corona, rendering without OpenSubDiv looks like in attachment, subdividing it once helps a lot (it's still not perfect), but subdividing it more, destroys displacement light direction.

2020-05-07, 17:19:44
Reply #5

maru

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Hmm, I can't see the upload. Which method did you use? Can you try the Dropbox one? Or you can PM me with a link from some other uploader of your choice.
Meanwhile, you can try this:
- Reset xform
- Convert the model to editable poly, select all faces, go to Edit polygons > Retriangulate
- Try toggling the new 2.5D displacement on an off in the Render Setup > Performance tab

2020-05-07, 17:52:07
Reply #6

rdm

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- Reset Xform did nothing
- Retriangulate did something. It's better, but still have visable artifacts
- Toggling disp. method did nothing


I used your web uploader. Now I used dropbox, could you check if files are there? Displacement.zip

2020-05-07, 18:41:05
Reply #7

maru

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