The delusional world of PBR

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  3 Weeks Ago
Originally Posted by kgs7165: PBR gives you some shortcuts, and productivity boost and these are nice things to have. My point is, you don't have to caught up on this too much. Utilize it's function, but if you want to break it, I don't think there's anything wrong about it.

Totally agree with this, despite seemingly to appear pro-PBR.

It shits me when we can't make artistic changes. I don't want to just excute realism, I want to make things awesome.
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  3 Weeks Ago
One more reason why current PBR workflow is not actually "physically based".

Textures.

Think about how major vfx / animation / game studios make their diffuse textures. Take whatever on google. cgtextures.com, even you took photos with your DSLR in ambient lighting, these pictures have specular on the images. Not polarized(you get this sometimes for digi double work). and how you usually make spec / gloss map? Starting with making diffuse into grey scale. Sounds familiar right? So in rendering, you're adding spec on top of spec. of course you can CC the source images look more diffussy- but on that point, not really physically accurate.

I didn't want to bring biased, unbiased renderer battle here but here's something interesting to read from Chaosgroup

https://labs.chaosgroup.com/index.p...ased-rendering/
and I totally agree on this one.

I also agree PBR is more of keeping consistency through out the process rather than what's physically accurate and what's not.

Thank you for sharing your insightful opinions guys.

Last edited by kgs7165 : 3 Weeks Ago at 07:41 AM.
 
  3 Weeks Ago
Originally Posted by kgs7165: One more reason why current PBR workflow is not actually "physically based".

Textures.

Think about how major vfx / animation / game studios make their diffuse
textures. Take whatever on google. cgtextures.com, even you took photos
with your DSLR in ambient lighting, these pictures have specular on the
images. Not polarized(you get this sometimes for digi double work). and
how you usually make spec / gloss map? Starting with making diffuse into
grey scale. Sounds familiar right? So in rendering, you're adding spec
on top of spec. of course you can CC the source images look more
diffussy- but on that point, not really physically accurate.

I didn't want to bring biased, unbiased renderer battle here but here's something interesting to read from Chaosgroup

https://labs.chaosgroup.com/index.p...ased-rendering/
and I totally agree on this one.


Yes that's why the B stands for 'based'. Its based on realistic behavior but does not exactly replicate it.
Things like diffuse/albedo maps are a good example. They aren't how it works in real life at all. What CG artist knows as a diffuse map is a rough approximation of what in the real world is a combination of very rough reflections and SSS.
Also, the BRDF's we generally use (phong, blinn, ward, cook-Torrance, ggx, etc...) are all just average approximations that give you control to make things look 'close enough'.
If you really want to simulate light and matter interactions realistically it gets quite a lot more complex.

And yes, the unbiased vs biased thing is totally irrelevant, misunderstood and overrated (again, thanks to marketing).

Last edited by ACiD80 : 3 Weeks Ago at 10:16 AM.
 
  3 Weeks Ago
edit: Comment deleted. I don't think the discussion will be productive.
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  3 Weeks Ago
Why not?...
Please don't edit yourself.
Tell us what you think
-R
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  3 Weeks Ago
It is not perfect but it is a lot better that what we were working with before. 10 years ago, access to a PBR capable render engine was expensive. Now you can use Cycles and a few othersto get some really impressive results. Of course you can poke holes in the model that are used to simulate light interactions and find edge cases where what is happening is not accurate, but for most cases PBR is a very good approximation of what is going on.

Is 3D modelling delusional because things in the real world are not made of polygons? Cheating is part of the fun.
 
  3 Weeks Ago
Originally Posted by RobertoOrtiz: Why not?...
Please don't edit yourself.
Tell us what you think
-R

I think this is just a case of different opinions about what PBR means to the industry, and the semantics of it's definition.

To me it's about the mindset of persuing physical accuracy so that we have the most accurate analog between the physical and the digital that is currently, computationally, viable. People who embrace PBR are people who want to place an Arri SkyPanel S120 where that same light was located on-set. When you look at a render and see the creature doesn't have little highlights on the left you don't tweak it in comp, you go back and throw a black matte below the face and change the rim light to something tighter and further back. It's using ACES, mapping camera response curves, always working to scene scale and using physically accurate force values in your simulation, it's researching the micro-surface details of skin and making them stretch and squash, it's using blood vessle simulation driven by the pre-fire muscle simulation and driving that into you SSS.

And it means that, if render times are within acceptable limits, you use an unbiased renderer. It doesn't matter if the images could come out the same from a biased renderer, in the factory production methodology of VFX you are building a pipeline now around this realism, adopting a mindset, and you want everything to be mathematically pure so that you have predictable results and clear guidelines for asset development.

I agree with ACiD80 that the difference between unbiased/biased is almost meaningless in most contexts but I view VFX as a large collaborative pipeline structure. And here we are, with unbiased renderers completely and utterly dominating the industry. I have friends with technical Oscars they won for their contributions to lighting who are absolutely PBR focused and have strongly embraced Unbiased rendering (just a part of what they embrace actually) and it's adoption in the industry. I don't think they use these terms as hype. I don't think they like unbiased just because it's cool. I think they see it as necessary to control the realism of lighting - they want to say "Stop cheating and do it right. When you see the flaws this way you'll know they come from your asset or lights."

Unbiased vs. biased isn't the important thing. Understanding the mindset of understanding why one is being embraced over the other, by very smart and technical people, is absolutely important.

I feel that objectively you can say there's been a change in the industry where we realise we don't need to fake so much of everything now. We don't want to. We want repeatable, accurate, we want a solid realistic base (as good as we can get anyway) from which to tweak creatively. We've taken the ideas of PBR, of keeping the maths accurate, and we've started to apply it to other areas of the pipeline.

I also think this has driven complex changes we don't usually talk about. Like the different way we review assets now. Or the number of AOVs we render. And the colour pipeline all the way from on-set through to final DI.

Just because we still use diffuse textures doesn't mean we should just give up an admit we're fucked and PBR is a lie. Look at the way we make textures now even - everything is 16bit float linear, we photo (yes, with polariser) when we can and we use complex maths to try to remove surface reflective contributions from the diffuse reflection contributions - look at megascans for example. We now use SSS on almost everything, even hair can have it now. We microfacet, we add irradescent thin films to things, microhairs.

And the thing is I totally agree that all this shit can be fakes with enough time and effort. But the goal is to bring it together into a pipeline which makes those things all normal. It frustrates me immensly to hear some people here acting as if this is just marketing BS. In gaming, sure, whatever. In VFX we don't necessarily use the term all the time but if you're not someone who embraces this philosophy you're out of the loop. Sure, we still don't do all this stuff all the time but many people want to, and that's enough for me.

And I self edited because I am sure these opinions will just lead to another shot but dismissive response as if I don't understand the technical nature of PBR. I find that annoying and frustrating but am willing to admit I may be arguing off topic of what ACiD80 and others think are reasonable interpretations.
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  3 Weeks Ago
It has made a useful difference to those of us in Archviz. By having a calibrated scene (Grey cards matching the HDRI & Realworld camera) you know your swatches will be 100% in the lit area of the scene. Clients can be fussy down to a hue/brightness difference of 2% for individual tiles/floor boards etc - taking this out of the equation is a breath of fresh air, not to mention you know that your models will appear the same scene to scene without having to retweak your materials (unless its for a specific purpose).

Dubcat goes into a good explanation on how to set this up here (Its a Corona setup but you can apply the same principals to any renderer):
https://corona-renderer.com/forum/i...p?topic=17712.0
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  3 Weeks Ago
I didn't read through the entire thread and I'm certainly not the expert to turn to but I feel it's a step to unifying offline rendering and realtime material.
 
  3 Weeks Ago
Originally Posted by axiomatic: I think this is just a case of different opinions about what PBR means to the industry, and the semantics of it's definition.

Yes that's exactly the OP's point (i think?).

For those who are quite experienced in off-line rendering it looks like 'PBR' is about physical based rendering in general which we've been calling physical *correct* rendering before in the off-line renderer world, which has been there for quite some time already.
To be honest though, calling it "physically based" is more accurate than calling it "physical correct" for reasons mentioned before (it all being still being approximations).

But when we look at what the new hype (which is started by the game engines) is about it's all about the shaders/materials and the workflow surrounding their creation. Thats why we see so many *new* PBR shaders/materials pop up in software but nothing about the lighting/gi, etc...
Probably because thats still not quite possible to do in realtime (remember, it comes from realtime engines).

So yeah, that's causing quite a lot of confusion and that's what I thought the OP was refering to?

The nice thing is that we now have kind of an unified workflow between game engines and off-lines renderers when it comes to shaders/materials/textures. Which is/was an important part of the PBR-workflow.
 
  3 Weeks Ago
Originally Posted by Octop: I didn't read through the entire thread and I'm certainly not the expert to turn to but I feel it's a step to unifying offline rendering and realtime material.

Exactly!

*filler*
 
  3 Weeks Ago
Originally Posted by axiomatic: I agree with ACiD80 that the difference between unbiased/biased is almost meaningless in most contexts but I view VFX as a large collaborative pipeline structure. And here we are, with unbiased renderers completely and utterly dominating the industry.

Could you name those renderers? Because most renderers used (and the way they are used) that I know of aren't unbiased.
 
  3 Weeks Ago
Originally Posted by ACiD80: Could you name those renderers? Because most renderers used (and the way they are used) that I know of aren't unbiased.

Arnold, Manuka and Mantra.
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Critcal feedback example #62: "Well instead of the Stalinist purges and the divorce and the investigation ... it could be about losing a balloon."
 
  3 Weeks Ago
I personally can't think of Unity and Unreal being without PBR anymore. The whole PBR thing gave the new games a big quality boost. So for me it's definitely no buzzword.
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  3 Weeks Ago
Originally Posted by axiomatic: Arnold, Manuka and Mantra.

I'd suggest you read the link "kgs7165" posted.
I'll repost the link for you: https://www.chaosgroup.com/blog/the...iased-rendering

You'll find that pretty much all renderer used in production (need to be fast) are biased.
Even maxwell render isn't unbiased (it clamps over bright secondary rays to reduce 'fireflies' and I'm sure it does use other similar biased trickery).

That doesn't mean you can't run any of them in an unbiased mode, but no-one ever does that because it makes it much slower for unnecessary reasons (no one will notice the difference) except maybe for some scientific reason(?).
We're still not at some point where render time isn't important (especially in animation and VFX)... maybe some day.

Last edited by ACiD80 : 3 Weeks Ago at 03:18 PM.
 
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