Author Topic: why aren't renderers realistic?  (Read 1267 times)

2021-10-10, 01:23:37

Feodor

  • Active Users
  • **
  • Posts: 116
    • View Profile
I've always been tormented by one question, why do renderers end up being unrealistic? Yes, there are renders that look similar to a photo, but when you look at a real photo, it is difficult to confuse it with computer graphics.
Is there a problem with the physics of light? Problem with textures? In AA filters? Is the problem in the elaboration of objects? . But even objects created using photometry do not look 100% realistic. 99.98% of the works are not given out by realism, and 0.02% are recognized if they are compared with reality. Where is the Achilles' heel and why is there still no render that would realistically be able to render an empty room without details and at the same time it looked like a photograph, even if it was just a white clean room?

2021-10-10, 15:20:13
Reply #1

burnin

  • Active Users
  • **
  • Posts: 1200
    • View Profile
For commercial work "good enough" is it. Those who seek better, know it only gets more expensive the more detail is added, so demands lower. 

Then, on creator's side, there just aren't many willing to take the path and, I also think while walking, observing, realizing more & more...
most ask same question....

Guess everyone has different priorities.

Once upon a time...


2021-10-28, 05:10:03
Reply #2

sebastian___

  • Active Users
  • **
  • Posts: 192
    • View Profile
I think one of the problems are the shaders/materials. And I don't mean they are not programed well, or at least I don't think so. But a material + maps have tons of parameters. PBR made everything simple, but even those few parameters have a range of possibilities. And everything gets much more complicated when it comes to choosing good values for SSS.
For example the attached pics, a simple material for murky or muddy water. But I spent so many hours adjusting, and I'm still not sure it's completely right.

That's why when you mentioned that even objects copied with photogrammetry can look off. Because the shape is photorealistic, if it has enough details, but photogrammetry doesn't copy the shaders.

2021-10-29, 10:45:34
Reply #3

agentdark45

  • Active Users
  • **
  • Posts: 577
    • View Profile
I'm going to ring the tone-mapping bell again.

Assuming everything "under the hood" is 95-100% physically accurate, light bouncing, materials e.t.c they can all be undone by bad tone-mapping. Think back to bad Vray renders of old with gross burnouts - the underlying GI simulation was still ok, but translating the dynamic range/colours as a DSLR/the human eye would wasn't up to scratch. I still believe it's one big area that overlooked in everyday CGI.

It also explains why even with a photo-scanned object, the rendered version in an good HDRI environment still won't look "right" in some cases. Another example; take a minimalist interior with next to no textures, different tone-mapping approaches can make the output look photoreal, and other implementations would make it look completely "fake".
Vray who?

2021-10-29, 12:50:32
Reply #4

sebastian___

  • Active Users
  • **
  • Posts: 192
    • View Profile
Sure, tone mapping is important to make the image pretty, or to emulate the look of good cameras.

But what about bad photos ? Made with cheap cameras ? They still look realistic.

I did a quick search for these:




2021-10-29, 15:26:14
Reply #5

agentdark45

  • Active Users
  • **
  • Posts: 577
    • View Profile
I see your point, but I would argue that even bad cameras are doing something different with how they process reality than how most baked in solutions work.

Couple of examples attached, note with the interior the "fake CGI gradient" effect on the walls - you just don't see that IRL.

With the two exterior examples, while both have great materials and model complexity, the white building image just has something about it that is head an shoulders above the brick building image in terms of realism. Note also that fake gradient effect creeping into the building on the far right in the brick building image.
Vray who?

2021-10-31, 13:05:18
Reply #6

sebastian___

  • Active Users
  • **
  • Posts: 192
    • View Profile
Maybe there is something about the tone-mapping too, I don't know, I can't say that I studied that too much, but in my eyes, I constantly see the shaders as a problem. And who can blame the artists ? Choosing the parameters for shaders is completely arbitrary.
  I would say if a renderer would implement a great tone-mapping, it could help more for realism, because a tone-mapping would be largely automatic. While the shaders would continue to leave lots of room for errors, because they will continue to rely on the user tweaking lots of parameters.

And in the images you posted I also see another constant problem which hinders realism. The world is far too perfect. Every line is impossibly straight, all the bricks are symmetric and identical down to the millimeter or even atom. Most surfaces are perfectly clean and uniform.

So to recap, I think these weigh heavily when it comes to realism:
 - shaders
 - the world is too clean and perfect

Even when it comes to "dirty" worlds, or nature or for example forest grounds things can look off, because again the user needs to make lots of decisions. The scale of the leafs and stones, scale of the bump map or displacement, reflectivity and glossiness of things and so on and on.

A good painter, or someone with a good eye would get better results in these cases.
I remember seeing a vfx reel for The Spiderwick Chronicles and they rendered with a low quality renderer with Vue, and as far as I know they also used low poly, low quality trees, and the images still looked photorealistic.

2021-10-31, 17:29:15
Reply #7

lupaz

  • Active Users
  • **
  • Posts: 678
    • View Profile
even if it was just a white clean room?

Because even a white clean room has billions of imperfections.
With unbiased render engines, if you add all that detail, you can fool anyone.

2021-10-31, 17:57:25
Reply #8

lupaz

  • Active Users
  • **
  • Posts: 678
    • View Profile
Look at the renderings of this guy.
If he crops certain areas, they look like photos. There's always something in the rendering that tells it's not a photo. But that's a matter of adding more detail IMO.

https://www.facebook.com/groups/1537914613171618/user/670182615/