No MIS in Kray 3?

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the3dcie
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No MIS in Kray 3?

Postby the3dcie » Thu May 24, 2018 9:59 pm

Hi there, the title of this thread says it all, I'm trying to do some renders of interiors with Kray3, only lit by an external HDRI (for a friend of mine who will be launching a new HDRI website...) and it the renders are grain as hell whatever samples I put in the quality settings panel!
To be precise, if I put something like 25000 samples it starts to look decent (!!) but the rendering times go through the roof!!

I'll try to put some samples of the renders if I can, but in the meantime the question is addressed to Grzegorz and/or Janusz, is there any MIS (Multiple Importance Sampling for those who don't know what it means...) in Kray 2 or Kray 3?

Thanks in advance, hopefully there is, because without that using HDRIs to light a scene is some sort of a "No Go", unfortunately. :(

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Janusz Biela
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Re: No MIS in Kray 3?

Postby Janusz Biela » Thu May 24, 2018 10:25 pm

Definitely you do something wrong. Post here basic scene with problem.
There some commands are not actual because they are bulid in core....maybe you used old command which override correct one in Core.

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the3dcie
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Re: No MIS in Kray 3?

Postby the3dcie » Fri May 25, 2018 6:06 pm

Hi Janusz, and thanks for your reply, I'm preparing the scene with another HDRI as I can't share the one I'm using for my scene, but here are 2 renders with the new HDRI which shows the effect (less than with the original HDRI but it's still noticeable) and what I'm talking about.

Image

Image

I'll send you a private message with the link to download the scene (don't look at the surfaces, it's a WIP...) as I can't share it publicly.
Thanks in advance, I hope I did a mistake in the settings and thta the noise from the HDRI can be eliminated without going too high in the illumination settings, as it defeats the purpose of using Kray, when all the other parts of the scene are great! :)

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Janusz Biela
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Re: No MIS in Kray 3?

Postby Janusz Biela » Fri May 25, 2018 8:24 pm

If you use HDRi as light source for interior then you choose the worst scenario. But send me scene via PM (wetransfer)

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the3dcie
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Re: No MIS in Kray 3?

Postby the3dcie » Fri May 25, 2018 9:04 pm

Yes I know there are better way for that but about all render engines now have MIS implemented (even LW2018 or LW2015!) and it does a great job at creating a non grainy lighting source from HDRI while keeping every aspect of the lighting contained in that kind of map.
Unfortunately those render engines aren't as good as Kray when it comes to deal with GI, by far!
So that's a tricky situation, for sure... :(

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Janusz Biela
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Re: No MIS in Kray 3?

Postby Janusz Biela » Fri May 25, 2018 11:00 pm

In my opinion HDRi as light source is very bad solution and no...physical correct. Modern light source is Physky Hosek.

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the3dcie
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Re: No MIS in Kray 3?

Postby the3dcie » Sat May 26, 2018 12:04 am

Probably, but in the meantime Physky is just a synthetic model of what the sky can look like and a very limited one, even more when it comes to extreme situation, like sunset or sunrise where it falls short to produce anything believable. And I have personally experienced skies when the "old" Preetham model was far more right in the colors proposed than the Hosek one, even if the later is 99% the better model...

Anyway, just to point out that PhySky alone is not the ultimate solution, and, for what it's worth, having MIS for background lighting (i.e. HDRI lighting...) is now so common that I really hope Kray 2 or 3 (i have both...) have it as well, that would be a big mistake, in my opinion, to have such a great render engine that doesn't have this "basic" feature! :(

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Janusz Biela
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Re: No MIS in Kray 3?

Postby Janusz Biela » Sat May 26, 2018 10:34 am

Personally I do NOT use HDRi as light source at all. It has all bad aspects...even reflection is not realistic (sic!). I mentioned it before in one topic why is so bad.

Correct lighting model for interiors are:
- light source: Physky/Hosek (I must put to G. one feature for de-saturation - this will be perfect for studio interior system)
- Skyportals (we do not need them in K3, we use LEM)
- correct tone map (we do not have this yet in K3)
- reflection boost option (my idea - I will discuss about it with G.)

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the3dcie
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Re: No MIS in Kray 3?

Postby the3dcie » Sat May 26, 2018 10:23 pm

Thanks Janusz for having a look at it!

As I said in the PM I just sent you, PhySky isn't an option for this scene (and the other ones I'm doing with the same HDRIs...) because the purpose of the scene is to show how good my friend's HDRIs are and how well they can light a scene!
So PhySky can't be an option in that particular case...

And it's really too bad if Kray 3, as advanced as it is, doesn't feature MIS as it's so common by now that I think every render engine out there does have this feature!
And given Kray 3 is a "pure' render engine with a quite high price tag already, it would be a pity if it didn't have that feature.
Rendering is as much about having choices as it is about great core engine.
I think I'll render those scenes in LW 2015 as it does have MIS, even if the GI can take a very long ti;e to clear from noise...

Thanks again for having a look and for your time! :)

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Keraressi Abdelkarim
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Re: No MIS in Kray 3?

Postby Keraressi Abdelkarim » Sun May 27, 2018 2:47 am

there is small trick in k3 hdri i found it last 3months.


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