Author Topic: Corona Bump is so broken  (Read 7956 times)

2022-12-19, 11:55:40
Reply #30

piotrus3333

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Yes, agreed. For better or for worse my assumption often is that the software is right and I am wrong.  Plus I am busy, so I can’t report a hypothetical issue.

For what it’s worth we always tell junior staff to be careful with Bump in Corona because it’s unpredictable and not that great.  Don’t get me wrong, we LOVE corona and all its features and it’s our primary engine.  But bump is not its highlight in our experience.  When I reduce blur it is better but sometimes kind of ‘rough.’  Anyway, would be cool to see this revisited by the dev team…maybe an alternate filtering method?

How about explaining clearly how texture filtering works? I bet this would be much more beneficial to junior staff than „it’s unpredictable and not that great”.
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2022-12-19, 12:28:07
Reply #31

philipbonum

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I've also noticed this, and it was very apparent when I compared a metal ball with scratches in "identical" scenes with F-storm, Corona, and Octane. I don't remember how Octane fared, but I do remember how well F-Storm did bump mapping, and even renders it faster because of a seemingly superior adaptive sampler(?)

I would also like this to be better in Corona if possible. I'm not sure if I tested this with low filtering, so it might be that this fixes everything, but maybe

On the other hand, I've had a lot more luck when using normal maps instead of bump maps.

PS: I'm not saying FStorm is faster at rendering, but it was faster on this very specific high contrast scenario(dark interior box, 1 strong light coming from a "window") And as far as I know, FStorm is still missing a denoiser...

« Last Edit: 2022-12-19, 12:38:12 by philipbonum »

2022-12-19, 13:09:49
Reply #32

dj_buckley

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+1 for not agreeing with the “if people aren’t complaining then it must be ok”.

Yes, agreed. For better or for worse my assumption often is that the software is right and I am wrong.  Plus I am busy, so I can’t report a hypothetical issue.

Guys, can you please explain who and where exactly said "if people aren't complaining then it must be ok"?

Can you please carefully read my whole post here https://forum.corona-renderer.com/index.php?topic=38682.msg207109#msg207109
and here (especially the bold points at the end) https://forum.corona-renderer.com/index.php?topic=38682.msg207147#msg207147

I literally said that we are aware of this issue and would love to fix it. The only thing I do not agree with is calling bump mapping technique in Corona "so broken".

In post #10 on this thread, the very one you just linked to, you said "On the other hand, we are not getting many reports like this, so it can't be that bad. ;) " - appreciate the winky face at the end suggests it's said tongue in cheek, but still ...

I assume people are saying Corona bump is broken is purely because that's how it's presented in the initial video.  In which case, it does indeed look broken wehn compared to FStorm and even Scanline, where it works consistently and exactly as I'd expect it to work.

To reiterate, a shader shouldn't look like a completely different finish (gloss or matt) depending on how close to it you are or what your filtering settings are.  This is what is happening in Corona, in the FStorm and Scanline examples, the finish looks the same regardless which is how it should be.  Gloss is gloss and matt is matt.

2022-12-19, 13:50:18
Reply #33

philipbonum

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Recreated my scratched chromeball scene again, and:
Fstorm:
A lot better looking bump, much more fine details, only creates bugs when bump is way beyond any normal use case
It does not seem like there's any filtering/blur on textures by default. Turning this up creates similar bump as in Corona, but without disappearing from far away.
Adaptive sampling is very aggressive on the scratches, making them show up almost immediately, but slower at removing the fine noise all over the image

Corona:
Filtering on by default, turning it "off" (0,01) produces much better results, and keeps it looking correct from far away
Not as good bump, trying to match the amount of bump/scratches in FStorm produces a "ring" effect
Adaptive sampling not really focusing on the scratches(?), so it needs a lot more samples, but at the same time the entire image becomes progressively better.

So in short:
Turning "off" filtering on textures is as always a good thing to do, maybe get in the habit of always doing this on bump? Increased rendertimes?
Room for improvement on bump in Corona in general. Take a look at the competition, always good to have something to work towards.
Maybe improve on the Adaptive sampler, it's very handy if it focuses on texture details like the scratches, aka quick feedback when editing materials

PS: Not sure if it's the Adaptive sampler that is deciding what to focus on when rendering, but that is my understanding of the feature.

2022-12-19, 15:34:45
Reply #34

Basshunter

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To reiterate, a shader shouldn't look like a completely different finish (gloss or matt) depending on how close to it you are or what your filtering settings are.  This is what is happening in Corona, in the FStorm and Scanline examples, the finish looks the same regardless which is how it should be.  Gloss is gloss and matt is matt.

This. I could not agree more.

2022-12-19, 17:14:31
Reply #35

danio1011

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Yes, agreed. For better or for worse my assumption often is that the software is right and I am wrong.  Plus I am busy, so I can’t report a hypothetical issue.

For what it’s worth we always tell junior staff to be careful with Bump in Corona because it’s unpredictable and not that great.  Don’t get me wrong, we LOVE corona and all its features and it’s our primary engine.  But bump is not its highlight in our experience.  When I reduce blur it is better but sometimes kind of ‘rough.’  Anyway, would be cool to see this revisited by the dev team…maybe an alternate filtering method?

How about explaining clearly how texture filtering works? I bet this would be much more beneficial to junior staff than „it’s unpredictable and not that great”.

We do explain filtering, too, of course.  That's kind of the point of this whole thread and also my comment:  even with a basic understanding of filtering, bump at glancing angles still acts in such a way as to deserve special treatment\explanation\occasional avoidance.  I'm thinking specifically about tree leaves.  We often leave bump off altogether for distant trees because we can get a natural look without it and find it to be more predictable when it comes to specularity (not to mention faster).  Again, YMMV but that's our experience and it seems I'm not the only one.

2022-12-20, 12:34:42
Reply #36

l.croxton

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Coming from FStorm and moving over to Corona (various reasons) I complete agree that the texture filtering/blurring as its currently defaulted too is more of hinderance than a net positive in my experience. Simply put I couldn't figure out why my renders were just looking better/sharper and then I just happened to try removing the blur and viola it was all good again. Not to say I don't use the blur in any of my renders in Corona, I tend to use it to help smooth out displacement/bump if I need them to be smoother but outside of that, I pretty much just remove filtering on anything.

Maybe a request could be made in the Corona converter that there is a "remove blur value" or "set blur to 1 or 0.1 or 0.01" ? which could also be tied to, all of scene or just selected.

2022-12-20, 13:56:19
Reply #37

romullus

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Maybe a request could be made in the Corona converter that there is a "remove blur value" or "set blur to 1 or 0.1 or 0.01" ? which could also be tied to, all of scene or just selected.

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2023-01-21, 22:27:13
Reply #38

mrsacan

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I was planning to create a thread about this but I learned the reason when I see this thread, as I see it was mentioned before.
I was wondering why one of my materials look different when distance (so, resolution) changes.



But in my case, this is not default value, it's the opposite way, I changed blur value to 20 (to smooth a sharper bump image), but I think it shouldn't depend on resolution/distance.
This is a serious issue imho.

2023-01-21, 23:46:56
Reply #39

romullus

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But in my case, this is not default value, it's the opposite way, I changed blur value to 20 (to smooth a sharper bump image), but I think it shouldn't depend on resolution/distance.
This is a serious issue imho.

I think you simply are using wrong feature. If you want blur that won't change its strength depending on resolution, then you need to set blur to the minimum and use blur offset instead. You will need to use Max bitmap though, since Corona bitmap doesn't have this feature.
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2023-01-22, 11:26:00
Reply #40

mrsacan

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I think you simply are using wrong feature. If you want blur that won't change its strength depending on resolution, then you need to set blur to the minimum and use blur offset instead. You will need to use Max bitmap though, since Corona bitmap doesn't have this feature.

I'm not sure what you mean, blur option works as I expected. Getting different results from different distances/resolutions is a completely different issue.


2023-01-22, 16:01:58
Reply #41

romullus

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Did you even read my message above? It has attached screenshot too. I will repeat it again - you're using the wrong tool for your task. Despite the name, blur in 3ds Max bitmap (and Corona bitmap) is not the same as blur in Photoshop. It acts more like an antialiasing - the smaller your texture is in the rendered image, the more it gets blurred. As i already said, if you need blur in traditional sense, you should use blur offset, or simply use photoshop and blur the texture permanently.

You can read about blur and blur offset in 3ds Max documentation: https://help.autodesk.com/view/3DSMAX/2023/ENU/?guid=GUID-8AE3643F-BDB4-498B-B220-92646FC8A562
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2023-02-03, 18:28:28
Reply #42

Juraj

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Can fully second what Romullus says, the names are weird and not what is commonly used as terminology elsewhere. Offset is very finicky though but I use it for displacement maps.
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2023-05-20, 17:42:34
Reply #43

Mr.Max

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I'm not sure if this was mentioned before but Renderman fixed it using a "Bump to Roughness" map that makes sure you will get good result from any distance.

also the recent update for VRay For Maya seems to introduce similar solution and according to Vlado when I've asked if it is the same and when we will see it in Max her replied
 " It is the same concept, yes - although the implementation is different. It is still experimental; if it works well, we will add it to other integrations."
https://docs.chaos.com/display/VMAYA/VRayBump2Glossiness

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2023-05-22, 12:27:49
Reply #44

romullus

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+1 for Bump to Roughness. Seems very nice idea to me.
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