What the heck is QMC?

General disscusion about Kray
obo
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What the heck is QMC?

Postby obo » Sat Dec 31, 2016 7:22 pm

Hi.
What is qmc?

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Janusz Biela
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Re: What the heck is QMC?

Postby Janusz Biela » Sun Jan 01, 2017 1:12 am

obo wrote:Hi.
What is qmc?

QMC = a brute force GI that samples every pixel.
Quasi Monte Carlo.
So if we have in Kray PM+QMC it means:
1. first phase is shooting interpolated photons and create map on which is based QMC
2. second phase is calculating GI samples as brute force (QMC)

This method is very close Path Tracing accuracy but much faster.

thomas
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Re: What the heck is QMC?

Postby thomas » Mon Jan 02, 2017 11:30 am

To put it simply:

With QMC, a number if rays is shot from every pixel to calculate the shadow and global illumination for that pixel. It is a "brute force" method because the process is not smart, but very simple: the more rays you shoot for every pixel the better the calculation becomes, and the less noise you have.

So with QMC it is:
general visual quality: accurate (with detailed shadows) but noisy if set at low quality
pro: perfectly exact result given enough rays fired
contra: no optimisations. Rendering for twice as long will make your result twice as accurate - no more, no less.


Photon mapping and Final Gathering methods are much smarter, will interpolate between results with smooth gradients, and generally do a lot of pre-processing or scene analysis to see where more rays need to fired, or more smoothing can be done between fewer data point.

So with PM it is:
general visual quality: smooth and noise-free, but lacking shadow or GI detail (and sometimes "splotchy")if set at low quality
pro: faster than QMC, and quickly noise free for large surfaces like walls and floors in Architecture Visualisation
contra: less shadow detail because some stuff is smoothed out. The faster the render, the more details are lost.

I hope that helps out a bit.

If you are going to make top-quality work I would suggest using QMC for now, if you have the time. The biggest advantage to interpolated methods is speed.

Cheers,
Thomas

obo
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Re: What the heck is QMC?

Postby obo » Thu Jan 05, 2017 1:37 am

Thank you.

But can someone post some setup? Just basics.

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Janusz Biela
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Re: What the heck is QMC?

Postby Janusz Biela » Thu Jan 05, 2017 9:15 am

Here basic scene with PM+QMC with good universal settings:
Interior_K2.png

GI_test.7z
(2.74 MiB) Downloaded 121 times

obo
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Re: What the heck is QMC?

Postby obo » Thu Jan 05, 2017 5:54 pm

Thanks a lot Janusz!

I'have only Kray 2.61 demo, I'm playing with it just for fun, but my time was above 12 minutes. Is that because demo or my pc? I have i56600K and 16GB Ram 2400

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Janusz Biela
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Re: What the heck is QMC?

Postby Janusz Biela » Thu Jan 05, 2017 7:35 pm

obo wrote:Thanks a lot Janusz!

I'have only Kray 2.61 demo, I'm playing with it just for fun, but my time was above 12 minutes. Is that because demo or my pc? I have i56600K and 16GB Ram 2400



Here is Cinebch R15:
http://http.maxon.net/pub/benchmarks/CI ... 15.038.zip
Download, unpack,test your CPU and post here your score.

obo
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Re: What the heck is QMC?

Postby obo » Thu Jan 05, 2017 8:58 pm

606

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Janusz Biela
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Re: What the heck is QMC?

Postby Janusz Biela » Thu Jan 05, 2017 9:09 pm

obo wrote:606

4700 here, so your times render is correct.

obo
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Re: What the heck is QMC?

Postby obo » Thu Jan 05, 2017 9:24 pm

Ok. Thank you very much.

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promity
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Re: What the heck is QMC?

Postby promity » Fri Jan 06, 2017 8:43 am

Strange thing - first time render was about 2 minutes, then i close all background programms and ta-da - 9 minutes, then i press render again - white render window for 5 seconds and crash.

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vgabex
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Re: What the heck is QMC?

Postby vgabex » Fri Jan 06, 2017 11:42 am

Janusz Biela wrote:
obo wrote:606

4700 here, so your times render is correct.


Janusz, is your config a dual E5-2697 v4?
I'm planning to step up from my 1700 cinebench point (i7-5960X @ 4.4) to a higher level.
Can you please help with your exact pcu, mobo and ram specs?

Thank you!

obo
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Re: What the heck is QMC?

Postby obo » Sat Jan 07, 2017 2:11 pm

I have a scene with these presets and it renders great, but than when i change lem luminoisty and hit render, result is the same. Why is that happening?

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Janusz Biela
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Re: What the heck is QMC?

Postby Janusz Biela » Sat Jan 07, 2017 3:04 pm

vgabex wrote:
Janusz Biela wrote:
obo wrote:606

4700 here, so your times render is correct.


Janusz, is your config a dual E5-2697 v4?
I'm planning to step up from my 1700 cinebench point (i7-5960X @ 4.4) to a higher level.
Can you please help with your exact pcu, mobo and ram specs?

Thank you!


This what we have in office:
CPU.png

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Janusz Biela
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Re: What the heck is QMC?

Postby Janusz Biela » Sat Jan 07, 2017 3:12 pm

obo wrote:I have a scene with these presets and it renders great, but than when i change lem luminoisty and hit render, result is the same. Why is that happening?


Ah I see now: inside are two lws (old and new one)
Use this one:
room.lws
(38.47 KiB) Downloaded 100 times


LEM panel is hidden from ray-tracing (only gives light, similar behavior like Area Light).
To do that you must put LEM to separate layer and setup unseen flags in this way:
ScreenShot008.png


and enable in Kray: Unseen by Rays...
ScreenShot009.png


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