Cleanup noise in Elements: Reflection and Shadow - Also LOOONG render times

[Morne]

My understanding is that its a clean interior, why would you need a dirt pass? Dirt/ao gives unnatural darkening in areas you normally would not have.
For the lighting i would not use mesh light either. Mesh lights produce more grain then regular lights. In this case, you are better off just using gi in that area from light mtl.
In terms of render time, any time you render with bruteforce expect your time to be high.
I will show you a diff setup when im home later today.

Thanks I look forward to your setup. As for the ligthmtl, I'm using direct light option as in the past I had splotches by not using it. The direct light fixed this, but ok that was a while back so things may have changed, I'll try without "direct light" option in light mtl. So you saying I shouldn't use AO as Brute Force already produces correct contact shadows?

- vrlightmtl with direct checked: do you really need it? ...from my test I'll say a big no, go with GI only
- ao pass: that one it's easier, just raise subds a bit

IMHO I'll switch to IR/LC + AO (with extra text could be better); it's a fake but it's faster; at the end the final decision will be based on the real complexity of the scene (if your renderfarm could afford long render time then go with brute forcr, otherwise stay with IR/LC

I'm hoping to permanently switch to Brute force so want to fully understand how it works. Also see the comments and questions I replied to Morbid Angel's response. Upping the subdivs in the AO is something I will try, but if Brute force already gives me the contact shadows etc then I geuss I dont need the built in fake AO or the extra text? I've never used extra text so not sure how to make use of it.

UPDATE:
In the meantime I've changed the multiplier from my "camera flash" hehehe (the vray light behind the camera) from 30 to 45. I changed the vraylightmtl multiplier down to 3 (but considering putting it even further down to 1). I've changed camera exposure shutter to 225 and iso 200. I brought DOWN brute force subdvis from 64, down to 16. Strangely bringing down brute force subs didn't effect the noise much and it looks almost a little less noisy (maybe due to the other settings I've changed that I mentioned)
AND
render times so far is DOWN from 1 hour 29 minutes, down to 28 minutes. So now just to clean the noise it seems. In the GI render element there is more noise however, but in beauty pass it looks slightly cleaner than before.

So to clean the beauty pass what do you suggest? maybe this:
- INCREASE material subdivs
- remove direct light from vraylightmtl
- decrease dmc and sampler from 0.005 down to 0.003
?

Your thoughts?

P.S. Most of the interior scenes I do nowadays consist of places being lit mostly by CURVED COVE lighting, that's why I use VRayLightmtl. It takes too long to devide a 50 meter curve into a hundred 500mmX40mm vraylights especially if the curve isnt a normal curve, but some irratic curve going all over the place. Then there are also mutli level cove lights sometimes up to 4 or 5 steps one above another (not in this scene however)

[zeronove]

so, here it is my attempt so far:

main changes without touching the core of the scene (mtl glossiness, lights intensity and position etc.)
- totally reset vray importing geometry, lights and camera in a new scene (I had issues with your file, I don't know why)
- lightmtl without direct light (only GI)
- ao subds raised
- various mtl subds raised
- global subds raised
- new image sampler set up
- clamp output and subpixel mapping checked
- "flash light" is now visible in specular and reflection (I like it more)

there are still problems with the glossiness of glass panels on the left, maybe tomorrow I'll double check them

sorry, no brute force but IM/LC

a quick note about cove lights, just remember that in general they are mainly decorative; in real life it's very hard to light a space in a good way only using that kind of fixture

[Morne]

Thanks, lets also see what Morbid Angel comes up with. I'm still hoping to get to the bottom of Brute Force inner workings and avoid clamp output and subpixel mapping. Doesn't it defeat the purpose of using LWF?
On a side note, how is the VRaySampleRate Element useful? I'm guessing the main idea is to a get a blueish image? I remember on my main large scene (the 1st image I posted in this thread) that there were a LOT of red parts in the samplerate element and I'm geussing that's bad?

@zeronove: I'll take a look at the scene you modified when I get to work tomorrow...

[zeronove]

Doesn't it defeat the purpose of using LWF?

In theory yes, actually no if you are not planning an hard postprocess stage.
one of the problem with your image is that it has some area with overbright colors and this is an additional work for the image sampler that waste time trying to antialiasing; you can try unchecking them to verify what has changed; to me not so much. It's true that the maths behind goes bad.

how is the VRaySampleRate Element useful? I'm guessing the main idea is to a get a blueish image?

I think the same, IMHO almost blue is the way to go; it means that image sampler it's not working so hard. Red means that it's working hard and needs an higher max value before turning to blue (or raising the clr threshold)

I would like to look at the Morbid findings as well

[Morne]

ok my material subdivs already gone to 512, brute force 64, and I'm STILL getting noise in GI and Reflection elements.
If I switch to light cache for primary and secondary, the GI element is clean. So does that tell me I need to up my BF even more to 128 or even 256??? That sounds excessively high!!??? or is that pretty standard?
I'm really trying to get to grips of using a brute force workflow, so far I'm not getting very far.

Any more suggestions?

[Morne]

no man this is getting rediculous now. Now I've changed dmc from 2,6 (or 2,100 cant remember what it was) to 2,256 and render times have gone DOWN from almost 2 hours to 18 minutes just by doing this! Noise levels still looks more or less the same. So render times comes down by increasing settings, but noise levels persists.

it's getting more weird by the minute!

[Morne]

ok now I have ALL subdivs on 512! (except for my "flash")
material reflection subdivs 512
light subdivs 256 (this light is my "flash" behind the camera)
BF 512
dmc 2,512 and 0.005
dmc sampler 1, 0.005
light cache 3000, 0.02 and use for glossy rays ticked. prefilter 100, trace threshold ticked and on 1
AO off
direct light for cove lighting off, warm yellow colour, vraylightmtl multiplier 3

with these settings it took only 21 minutes to render at 720p on my i7 2600K with 16GB Ram!
render times are BRILLIANT and noise is a little less visible in RGB beauty but still there! Do I really have to change subdivs for everything to 1024?
This is alsmot impossible to comprehend. One would think that with these settings it will render for weeks. WEIRD! Can anybody explain this?



maybe I need to restart my pc

[zeronove]

Do I really have to change subdivs for everything to 1024?

It seems to remember that maximum subds value is 1k and the big issue with ultra high subds is that mat editor become laggy; a workaround is the global subds multiplier

[joconnell]

Yep - hit the same thing yesterday trying to clean up the floor! You can set the subdivs to higher values with maxscript but the ui is locked to 1000 max.

The code for it is select the object with the material you want to change, and then type $.material.reflection_subdivs = 2000 in the listener (note, only works for objects with normal vray materials assigned)

[Morne]

is it a common thing to have such high subdivs?
I now also have global subdivs on 4.
Does that mean my 512 subdivs on my materials, the 512 BF etc all is now 512X4?
hardly does any changes to render times now and no changes to noise, but STILL noise!
the sample rate element is already flat blue
so what else to do? put global subdivs higher and higher and higher?

It's almost like I have an override on settings and no matter what I do, it stays the same

[Pixelcon]

Wasn't the "about noise in general" thread reaching some conclusions to do with render times not necessarily respecting dmc min/max settings and that just going crazy with subdivs everywhere isn't the answer? That the dmc is a very complicated beast and the literature linked from that thread while confusing, is the way forward in understanding how and where the dmc distributes samples across your scene? I may be way off... Fyi I think i read bertrand has started using IM/LC due to BF noise in vray 2

[Morne]

Wasn't the "about noise in general" thread reaching some conclusions to do with render times not necessarily respecting dmc min/max settings and that just going crazy with subdivs everywhere isn't the answer? That the dmc is a very complicated beast and the literature linked from that thread while confusing, is the way forward in understanding how and where the dmc distributes samples across your scene? I may be way off... Fyi I think i read bertrand has started using IM/LC due to BF noise in vray 2

no conclusion has been reached as far as I can tell. In Vlados quick tests he could not find a problem with dmc in VRay 2.0. So the question still remains. How to cleanup an image (this particular one), using BF
Just setting the subdivs higher and higher does seem a bit odd to me, which makes me think I'm doing something else wrong somewhere.

[super gnu]

imho, whilst BF is great for animated geometry and exquisite stills, its still prohibitively slow for flythrough stuff.. your scene there is very simple. if you add textures and shop interiors etc, you might find no amount of tweaking will get your rendertimes down with BF. its simply not fast...

Dmitry seems happer than most with long rendertimes, but i remember reading somewhere about his rendering hardware.. i dont thing many have access to such a pile of kit without paying for render services.

if you ARE doing flythrough stuff ( and you dont actually specify so this might be a pointless post) then the rendering speed gains from using nicely detailed precalculated imap and lc well, far outweigh the time needed to set up. (again imho)

[zeronove]

but STILL noise!

I suppose you already know about this
http://www.interstation3d.com/tutori...yfing_dmc.html

if that content is correct your noise is caused by high image sampler values: your high mat and light values are dropped down by the high value coming from the sampler that probably now has a threshold too high to be engaged (this cause the flat blue sample rate element and fast but noisy render)

[Morne]

so then how do you suggest I fix it? Right now I just want a clean BF render (and I'm less concerned with the times)
I'll try and get a clean image 1st with BF, and then worry about times I think

(with my current settings on my MAIN BIG scene with global subdivs on 4, the render takes 58 minutes which is acceptable, the noise isnt)