interior render, from FG to QMC

[brownie]

Hello all,

I'm currently trying to switch from FG renders to QMC. With the help of Janusz and some other Kray users, I manage to get some good result for studio renders.
But for Interiors, I can't get clean renders : images are always noisy even with what supposed to be high setups.

Now I really want to reach a new step in quality, and go from not bad to very good.

here is the full FG version and a part of the QMC one :

[Janusz Biela]

The noise should be almost clean with FG 100/800 (of course it`s small still but using Denoiser II in After Effect or standard denoiser in Photoshop you will clean up it)

Your noise comes from low reflection blur set-up.
Now You have to choices:
1. Increase quality of blur (for example min/max 500/2000) - bad choice
2. keeping blur quality around min/max 200/500

To keep low quality of blur and still get good effect you need keep light in small power especially Luminescence. Never put luminescence over 200-300%. Also same situation with Physky or another source of light from outside. Keep all sources of physical lights (Area, IES) also low - it will prevent noise also.
Setup for QMC - there is nothing to setup actually, only two thinks: FG min/max and Path Passes (important!)

Setup for Final Gathering.

[brownie]

Thank you so much, Janusz.

If I keep a low level of light, well...It's getting dark of course. I've seen in a previous post that you mentioned that we have to add lights, which is a bit disturbing for me : do I have to dub existing lights, add ceiling lights, or what I call "camera" light in other words a light panel from behind ?

And for the windows : areas or lumi (I know it's been debated a hundred times here !) ?

[Janusz Biela]

Thank you so much, Janusz.

If I keep a low level of light, well...It's getting dark of course.

Yes! and this is the biggest problem: how to bright up scene. You can:
1. Use Area Lights in windows (you must)
2. turn ON all lights
3. Use sometimes area light from ceiling (you must)
But by this you will get soft light and no problems with blur.
Because Area Lights are simulated in Kray you will get some noise, especially when light is close walls - so be careful with that. Area light doesn`t be size of widows - it can be much slower. Kray 3 has now new system for Area Light without noise and fast render but about this, later.

I've seen in a previous post that you mentioned that we have to add lights, which is a bit disturbing for me : do I have to dub existing lights, add ceiling lights, or what I call "camera" light in other words a light panel from behind ?

And for the windows : areas or lumi (I know it's been debated a hundred times here !) ?

Yes this is the most difficult problem in renders: how to deal with light sources. I suggest Area Lights, slower but I think better.

[brownie]

Hi,

This is where I am. I've applied most of the settings suggested by Janusz, except for Tonemapping, 1.6 , 5.0 gave me washed render.

Now I get a rather clean QMC render with 50% areas in windows, 5% areas on ceiling. I think I should reduce all that.
With Area light I had to set the falloff and choose inv2 with 5m, I don't know if it's good.

With QMC I get very good contact shadows, and avery natural overall lighting.

But I have to keep on pushing to get an excellent render, advices are welcome.

[Janusz Biela]

Hi,

This is where I am. I've applied most of the settings suggested by Janusz, except for Tonemapping, 1.6 , 5.0 gave me washed render.

Be careful with that high values. Keep close gamma 2.0. Problem is that when you rise too much gamma (I know you want brighter scene) you lose color levels: white start be over bright , dark start be gray .
I suggest keep gamma around 1.6 .
If you add also Exponential - keep it also low (2.0)
I add some exponential values to render because is hard too keep light in good acceptable level. Most users use only Exponential because is easy with light but after that colors are bad (it is very strong tone map).

Now I get a rather clean QMC render with 50% areas in windows, 5% areas on ceiling. I think I should reduce all that.
With Area light I had to set the falloff and choose inv2 with 5m, I don't know if it's good.

This Area Light where is curtain should be size of window but before curtain inside room - is important just receive light from this region (Do not put this light between window and curtain!)
Keep this light also far from walls (this noise comes from not tone mapped strong light and it is changed all ready in Kray 3.0 , no noise any more form Area Lights and finally fast render from them! It is special code in Kray which interpolated better this function from Lightwave)
Keep always inv2 for physical lights , second parameter with distance is less important. I try keep non stop same level for windows light (5 meters) because using non stop same values I have no doubts what level of Area Light should be in next scene - save time for prerenders.

With QMC I get very good contact shadows, and avery natural overall lighting.

But I have to keep on pushing to get an excellent render, advices are welcome.

Actually is no differences between QMC and Final Gathering in general light. The difference is only in sampling - in QMC doesn`t exist interpolation so samples are perfect. Of course QMC take information from photon map and if this map is bad it can appear Light Leaks (error in wire, error from Node). Important is to get clean photon map - this can give only Skyportals system and keeping soft light levels especially luminosity levels. For Skyportals we must wait for K3 when Physky light will be visible by this system.


The time render is very long. It is low end CPU? For i7 12HT this scene and resolution should take around 10-15 min.

[brownie]

Hello Janusz,

I've tried to follow your guidelines, and... it's getting worse.

I'm a bit puzzled. PLease consider that I don't want to bother you, but any further help would be appreciated.

(long Rentertimes are due to low-end computer, so that point is not an issue.)

[Janusz Biela]

You did not write what is your CPU.
I am on the forum to "bother me" ...so do not be afraid asking whatever you want (I am not Alpha and Omega but if I do not know something I dig for information or I make just a couple tests in renders)

Please confirm me what CPU you have because I suspect something wrong in your set-up but first I have to know CPU.
In extreme situation you can send me scene (without furnitures) via www.sprend.com to janusz.biela@gmail.com

[brownie]

Thank you Janusz

My CPU is a Core2duo 2.Ghz.

I'll send you my scene, it should clarify most things.

[Janusz Biela]

Thank you Janusz

My CPU is a Core2duo 2.Ghz.

I'll send you my scene, it should clarify most things.

I am not sure but score for this CPU in Cinebench (CPU) is ~1.3...so very, very slow.
Standard Dual Xeon (16 core/32 HT) has 24 pts, i7 CPU (6 core/12 HT) around 8.5 pts
...but still in my opinion time render is long
Also I suggest not to use QMC with this hardware.

one from many web pages with scores:
http://www.stenoweb.net/wiki/index.php? ... ch_Results

[brownie]

Hi Janusz,

I've uploaded on Sprend my zipped folder containing my scene. As previously said, my wish is to switch my basic method from FG to QMC, no matter my CPU is (sooner or later I'll get a brand new super fat Mac ).

Any help is appreciated and precious for me and some of other users. Thanks for that.

[Janusz Biela]

Here my fast test. Interior is pretty much difficult to render: there are very small windows and very few. For that scene must be small trick: Area Lights in windows must be bigger then windows holes.
Test in QMC mode.

[brownie]

A big, big thank to Janusz for the help. Now I try to understand each parameter, and I'm sure I'll switch to QMC workflow asasp.

I will post my updated renders soon

[Chumarin Ruslan]

I had a scene with QMC settings Kray She was lost. Janusz Biela please send a link to where I could see the scene QMC

[Janusz Biela]

Here update

- Instead Area Lights I used LEM lights
- if you want ultra quality you must setup FG min/max over 2000/0...but time will be horrible ...is just QMC (not interpolated GI). Of course much faster then Path Tracing.
- for preview images you can setup FG 100/0 with no AA (example in file) This is enough to see scene and light
- when QMC is selected, FG tab has only one thing working there: FG min/max. rest options are disabled (you can change values but they do not work)
- more FG - better quality - longer time render. Example: FG 100/0 big noise and fast render, FG 500/0 acceptable noise slow render, FG 1000/0 very small noise - long render...etc.
- minimum AA Grid 3, but better Grid 4 or even 5. This helps reduce noise.
- because QMC is not interpolated method the Global Illumination always is perfect (very close to Path Tracing) but: GI samples in QMC method are calculated from Photon Map and if Photon Map is bad also GI calculated by QMC engine can be bad (light leaks). doesn`t exist Splotches effect in QMC method! Splotches errors comes from not enough samples in Final Gathering so in QMC always we have maximum GI samples (infinite) which are determinate by level of noise. This Light leak effect comes from bad wire, too strong LEM or Physical light, not supported Node. These bad things determinate quality level of photon map and even QMC (calculation comes after shooting photons) can not help.
In the end: QMC is something between Final gathering and Path Tracing.
QMC is around 2-4 times slower then Final gathering with almost the same quality.
QMC is around 5-10 faster then Path tracing
Final gathering is around 10-20 times faster then Path Tracing

Selected method strongly depends from hardware

...but is one hope: K3 has NEW and very accurate Photon Map engine and comparing to old one will it be revolutionary.
This is very important because having very accurate Photon Map solution we can render in Final Gathering with quality of QMC or even Path Tracing ...of course without noise.