Optimising Brute Force for clean interior image

[coolhand78]

has anyone here needed to set the subdivs for brute force to 500 and above in order to produce a clean image for an interior shot?

i'm having a great deal of difficulty in getting brute force to produce an image that isn't ridiculously noisy? even when using both the universal settings and grant warwick's optimising methods the renders are coming out incredible noisy after render for some 20 odd hours... (single machine i7 5820, max 2016 vray3)...

[Morbid Angel]

That does sound high, are you using lightcache for secondary? is your scene complex?

[vlado]

Like Dmitry said, that doesn't sound right. It would be best if you can post more some images or send some part of the scene to support@chaosgroup.com so that we can check what's wrong.

Best regards,
Vlado

[mdcvis]

How's the scene lit for starters? Are you using a dome light with HDRI for ambient, natural light and that's it or do you have interior lights on and light planes in the windows etc?

I only ask as literally last week i spent an hour trying to clean up and interior scene until i realised i'd loaded a jpeg environment instead of the hdri file next to it

[coolhand78]

The scene is lit by a single HDRi (peter guthrie), not an overly complicated scene at all - this was a test render at 1500px that took a couple of minutes shy of 5hrs which is an exceptional amount of time in my opinion. I've played around with everything I can think of, even merging the whole scene into a clean file and resetting the render settings, but to no avail. The only thing I haven't tried is turning off divide shading subdivs and going through Grant's method for that... but I don't know that if I went down that rabbit hole it'd yield the results I'm after.

I'm rendering on my single i7 5820k 32Gb Ram GTX970...

[super gnu]

but.. which version of vray are you using? you are using an old methodology of very high subdivisions rather than letting vray do it all for you.

you mentioned resetting vray, does this mean entirely to the new 3.3 defaults with subdivs greyed out?



i cannot explain your massive rendertimes, but i would say

a) your aa max rate is too high for a still image. for a print res. image id not imagine over 12 was necessary. animation is obviously a different story.

b) 5000 subdivs for lightcache is unnecessary. the default is usually fine, or cranked a bit.. but i very rarely go above 2000.


c) you could run into issues if your interior is lit only by an hdri through a small window, and youve cranked the exposure to get it bright enough in there.

in this scenario either add some internal lighting, or a vraylight set to environment portal in the window.

d) is an hdri really necessary for a bit of light coming through a window? hdris are rather harder to sample, and id doubt it was much of an advantage over the standard vraysky, or even a vraylight in the window with a flat colour or gradient on.

[stevesideas]

Have you tried a vray sun system to rule out the HDRI ? Also, are you using any exposure tweaks in VFB or is it default ?

[mdcvis]

Yeah I can see you've been pushing settings very high to try clean this up which makes me think there's something going on with the HDRI maybe. This noise is very much in the secondary bounce category as well so you need to concentrate on this area, not your min and max AA values.

I'd be tempted to reset your vray render settings and try Vlado's recommended default. You don't look to be on vray3.3 yet so you would need to set your global subdiv multiplier to 0.0 to wipe out your adjusted material and light settings and then, if i remember correctly its 1 and 24 (min and max AA) and increase min shading rate up to 6 (to increase samples in the secondary bounce area) and then leave GI on brute force 8 (doesn't technically matter anymore as your global subdiv set to 0.0 overrides this) and LC left at 1000. Your noise and clr thresh down to say 0.006 and noise thresh lower at say 0.003

If these still give you really bad noise it's a lighting / HDRi issue. This includes not getting enough light into the scene. A few vrayplane lights in the window would help.

I'll try find Vlado's orignal post on this but there are plenty of examples of this out there now, seem generally the way to go these days. Lele has lots of posts on it if you have a quick search but they relate more to the latest Vray.

Good luck!

EDIT: link to Vlado's sampling post...first post in thread http://forums.chaosgroup.com/showthr...ettings+global

[khoross]

if you are using the old methodology.
there is a flaw in your method, in interior it's the minimum shading rate and the minimum sample that should be high like MSR 6 and min sample 16.
and the AA should be lower , cause basically your noise should be solved by shading. not by direct sampling.

[coolhand78]

Thanks for the replies, I'm using vray 3.2 currently.
I've tried the new 3.3 settings (in 3.2 however) and it didn't really make much difference tbh...

There's a massive glass window that runs the length of the room and returns down one side so no issues with letting light in...
I was still under the impression that portal lights were old school and not really used any more... maybe I'll give that a go and see what happens.

As the images show, the subdivs on the materials are quite high (200 in the case of the cabinetry) and I've attempted increasing MSR and min samples as suggested...

I never usually use LC subdivs of 5000 usually I'd just opt for 1500 or 2000 and it's normally not an issue, but I thought it worth trying.

I do have a colour correction on the HDRi to reduce the saturation, the gamma is also set to .7...

There are no tweaks in the VFB it's all set to default.

the first real test i did of this scene (using settings different from above but producing a very grainy result) was a 3k and took 21hrs...
i'd have expected it to render in at least half that time and be as sharp as knife...?

I'll take some of the suggestions here and see how i go...

[mdcvis]

Out of interest do you get the same noise with all the furniture hidden and an override material (mid grey) on? Window excluded obviously to allow the light in.

[coolhand78]

The other thing to note, is that in order to render out a clean image I've reverted to Irrandiance Map, once again with stupidly high settings and extreme render times, but it does render clean...
it takes forever but it does actually get there...

I'm only rendering the image out at 3k as it is purely for web, but would rendering it larger in some way be better option?

[coolhand78]

Out of interest do you get the same noise with all the furniture hidden and an override material (mid grey) on? Window excluded obviously to allow the light in.

I cant test it at present as it's just over half way through rendering, but i will test it as soon as it's finished.

[coolhand78]

the scene renders quite well with an override material set to medium grey - what really seems to be killing it is the forest pack.
I haven't cleaned it up completely but it does render much faster and i'd feel more confident that I could clean it up using the usual methods that have worked for me in the past...

on my test scene at 1500px without the forest pack trees it renders in just under 10 mins (with override mat on) unhide the forest pack - over 30mins...
that's a 300% increase...!

any advice?

i'm just using forest pack lite with some R&D iTrees and HQ plants...

[mdcvis]

Try setting the individual subdivs on the forest pack objects down to 0.0 This will give them only one secondary bounce and should limit how they effect the rest of the scene and cut render times.