Author Topic: Tonemapping - Plz Halp  (Read 115765 times)

2020-04-30, 11:55:54
Reply #75

cjwidd

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[...] best example being flesh flash light.

*edited for general audiences 😄

👀
« Last Edit: 2020-04-30, 12:42:04 by cjwidd »

2020-04-30, 12:03:14
Reply #76

romullus

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LOL
I'm not Corona Team member. Everything i say, is my personal opinion only.
My Models | My Videos | My Pictures

2020-04-30, 12:05:01
Reply #77

cjwidd

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@JurajTalcik Are you referring to this article about the uncanny valley?
« Last Edit: 2020-04-30, 12:10:35 by cjwidd »

2020-04-30, 12:37:53
Reply #78

Juraj

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False security of grammar checker 😀
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2020-04-30, 17:12:07
Reply #79

Fluss

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Also, what's make Fstorm appealing on the first sight, to me at least, is that the tone mapping curve is not driven by the LUT so you can use the LUT slot for other purposes. If you look at Johaness workflow, he is using LUTs to stylize his renders (desaturate colors, shifting black etc etc..)

Just wanna add that I know curves are there but I find them uber-sensitive and it's impossible to fine-tune, I never use them.

2020-04-30, 17:40:52
Reply #80

lupaz

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Guys, I really think that the evidence is clear: Renderings done with Corona are more easily recognizable as CGI than those made with Fstorm.

Really, tonemapping is not IT. Even if the Corona team re-works the tonemapping area, it may get better, but it's not it.

I was just at the Facebook pages of Fstorm and Corona.

It took me a while to find images in the Fstorm group, even by what it seemed the most inexperienced memebers, that didn't look like a photo.
Then I went to the Corona Facebook page. The fist image I found was obviously a rendering done by a not-so-experienced user and there was no way to tell my brain that it may be a photo.

See images below. I tried to take the worst images in the Facebook pages. I think the evidence is obvious: It's easier to make photorealism with Fstorm than with Corona. And I cannot believe that the discussion is about improving tonemapping to get the photorealism that you get with Fstorm by default. (Very clear to me with the image of the laundry room, made with Fstorm. It looks like a toy, but there's a realistic quality to it, with seemingly no effort)

It's like when we were having this conversation in the Vray forum just when Corona was released back in 2013 or so. The issue is not tonemapping.
IMO the issue has to do with the level of bias-ness: Both Fstorm and Corona are biased render engines. But the way Corona does the bias by default is not as good as what Fstorm does.








Even in this image, obviously with a lot of detail, I can tell that boat is fake.



« Last Edit: 2020-04-30, 17:47:26 by lupaz »

2020-04-30, 17:46:14
Reply #81

Fluss

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I don't know if image compression ruin all of these but to be honest, the last render looks the best of all of those to my eye

2020-04-30, 17:48:28
Reply #82

lupaz

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I don't know if image compression ruin all of these but to be honest, the last render looks the best of all of those to my eye

Yes, I added that render there to show that even an excellent work with a lot of detail, in Corona, still doesn't look like a photo.

2020-04-30, 17:54:01
Reply #83

lupaz

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Even on this image: Very simple scene by what it seems to be a not very experienced artist:
Except for the window, my brain may believe this is a photo.


2020-04-30, 18:04:20
Reply #84

Juraj

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Since I never tested fstorm I cant tell what causes this but I noriced this on Bertrands scene he sell. The Fstorm has much stronger direct light. Why is it? Clamped GI? Is it accidental or intentional. It gives the space more readable light in way that I doubt is due to tonemapping.

Someone would have to do a deep dive becayse the features have odd parity in behavior. Fstorm HDRI has two modes (weird option to cut off direct light?), their portal light effectively becomes new area light (like one option in Vray).

Very hard to pick out what exactly is the cause with so many variables.

With Dubcat, we suspected the shader. I wonder if something lije OrenNayar wouldnt cause more highlights from durect light?
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2020-04-30, 19:04:54
Reply #85

Fluss

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There you are, the effect on this one is more what we are referring to when talking about Fstorm TM. I wouldn't even call this image realistic, there is a bunch of stuff that are off but there is something in it that feels natural indeed.

2020-04-30, 19:25:32
Reply #86

romullus

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Those comparisons are meaningless when viewer is even more biased than renderer...
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2020-04-30, 19:39:01
Reply #87

agentdark45

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There you are, the effect on this one is more what we are referring to when talking about Fstorm TM. I wouldn't even call this image realistic, there is a bunch of stuff that are off but there is something in it that feels natural indeed.

The Fstorm TM tonemapping magic imo is mostly to do with the way it handles highlights/burnouts, the falloff to extreme blacks (and colour behaviour in general) and the ability to produce a nicely contrasted image without sacrificing the previously mentioned elements. The Corona VFB crushes the hell out highlights/blacks when trying to achieve a contrasty photographic image, either via a combo of stock HC/contrast/LUTs (see the previous comparison examples by lolec and my detailed observation notes). The way Fstorm clamps highlights and the gentle roll off to true black is beautiful, it isn't in Corona, period.

Again, I cannot stress enough that the handling of highlights and blacks cannot simply be fixed by arbitrary curves/LUTs inside of Corona's VFB - sure we might be able to get close (read: 90% as close) by rendering out a linear 32bit image and fooling around in photoshop - but goddamn, what a painful workaround.

I'm also starting to think part of the Fstorm magic is the internal colourspace, take a look at the examples on Chris Brejon's ACES page (at the very bottom and click left and right): https://chrisbrejon.com/cg-cinematography/chapter-1-5-academy-color-encoding-system-aces/ - notice that even GI gets affected along with colour bounce, most apparent in the red ball.

Again I should stress that I am nitpicking here, Corona has decent tonemapping options but when compared to FStorm it simply isn't on the same level after using both engines extensively. Sure, I can produce nice images in Corona (and I do for all interior work), but if I wasn't as limited with Fstorms materials + VRAM I would use Fstorm everytime. For high end product shots I use Fstorm exclusively - I have tried to match a lot of my scenes 1:1 in Corona and something is always off in comparison (overly clamped highlights/highlights too burned/colours being weird unless manual silly tweaking/blacks being crushed when trying to achieve more contrast...the list goes on).

« Last Edit: 2020-04-30, 19:45:10 by agentdark45 »
Vray who?

2020-04-30, 19:49:14
Reply #88

lupaz

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Those comparisons are meaningless when viewer is even more biased than renderer...

Not sure what that means.


For further comparison some images below.

Could DOF have something to do with it?
The hotspots in Fstorm are very good. ACES?

This is the what Vlado says about biased and unbiased rendering https://www.chaosgroup.com/blog/the-truth-about-unbiased-rendering
I believe that how Corona and Fstorm choose to be unbiased is what ultimately makes the difference in realism.

CORONA:







FSTORM:















2020-04-30, 21:06:02
Reply #89

cjwidd

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I really did not create this thread with the intention of comparing FStorm and Corona Renderer...