Best optimization tips for rendering Archviz scenes in Arnold?

[jnvfxartist]

Hello Arnold Community.

I'm just about 99% done making all the 3D models for my first Archviz scene (the first floor of an entire house) and before I actually slap on my materials and hit render, I'm wondering what is the best advice for optimizing HYPER photorealistic scenes with Arnold?

I should mention I do have experience with the PBR pipeline, I know how to unwrap/texture, digital sculpt and displacement etc, but I want to bring my portfolio quality up so as to match actual professional Archviz work in the industry.

For reference, this is the type of target I want to hit:

https://www.artstation.com/artwork/6aOkDr

https://www.artstation.com/artwork/aRd3lL

And this is my current Kitchen/ground floor I want to render (still has a mix of placeholders)

So far I've attempted the following:

-I will use a lot of instances

-I will swap out low poly models for high poly ones saved out as procedurals

-After doing several lighting configurations, I found using Quad Lights + Distance Sun offered the best trade off in noise vs render speed

-I optimized the house geometry so the first floor of the house gets the most lighting

-I've included light portals for every window

-I will make use of .tx file format over jpeg textures

Sorry if this sounds like a really long write up.

[madsd]

Put in some lamps and make some test renders and post those.
Do note that 99% of the light comes from the environment in those examples you posted, the artificial lamps contribute very little to the over all lightning.
It's hard to tell if you got windows to the exterior, or you are going to utilize artificial lamps entirely.

Else there is not a lot to it, shaders and models can very easily throw off the perception of the nice factor regardless of light quality.

[jnvfxartist]

Here is a test render using just lamps

Here is a test render I did using just quad lights (outside windows)

And here is a test render using quad lights + distance sun (apologies for low resolution. It took the longest to render)

In terms of windows, there are 3 at the back, 1 near the staircase on the second floor, and 1 at the front entrance.

[madsd]

- Check if you got 3 diffuse bounces in the render settings, default is 1. 3 gives a lot more illumination in the same exposure range.
- Crank the exposure up significantly and dial down "highs" to control overexposed areas where you dial them back. You need to pack the exposure levels more tight, right now they are very seperated.
- Feed in the artifical lamps after than from the bottom up, meaning low light and add more till they look right based on the above light model.

Right now, you got too big of a difference and contrast going in the light model, the sun is over 1.0 and surfaces which are not directly lit are very dark.
- You crush the blacks in the end to make the shadows pop.

Try run through the first 3 items first.

[madsd]

Are you grading with max frame buffer or VFB+ ?
If max framebuffer enable Photometric exposure control which gives you high, mid and lows. The VFB+ Framebuffer has a lot more grading options.
Grading and calibrating lights are part of the same equation.

[madsd]

See difference, I stole your jpg file and cranked mids and lowered the highs and crushed the blacks a bit and lifted the blacks ( using levels in post, but you got those at disposal at render time as well )
You'd want to go down that route just at render time

[jnvfxartist]

For the exposure, I used the Physical Camera with mostly default settings. There are also 3 bounces.

Here is the retweeked version. Am I doing it correctly?

[madsd]

That would be over the top.
Keep the mids at 1.0 and just lower the highs from default .2 to something lower till the burnouts disapear.

[madsd]

Use active shade so whenever you do something, you can see the change realtime.
Ideally for look dev, use a GPU + OptiX denoiser, the combo is insane, interiors renders in mere seconds.
I just opened a working case here.
0.01
0.5
1.0

Not saying it will work for you but its a starting point ~

[jnvfxartist]

So here I've made the changes to the exposure again,

Here is also the same scene but the distance sun turned on. Is this correct?

I'll admit, it was suppose to be a sunset so I changed the quad lights to a blue temperature instead of the more overcast grey. Or can I reuse these exposure settings under any lighting condition?

The hardest part is juggling the sun's exposure intensity. I'm not sure if the sun should be 8 or 16 (to match the sky).

[madsd]

It's better.
You should play with the sun so it does not nuke everything it touches. It's too strong IMO.
But, now - shaders comes into play, so shade everything, so you can get back to light model and tweak the details up.
In general you would want to do the final grading with the shaders all done, do the final tiny adjustments on skylight, sun power, and colors of both items, in junction with master grading.

So, don't get too caught up in the light model now. But you are now able to do some reasonable quick renders with textures and shading going.

Then in end, pack the contrast up a bit more, so sun sits closer to the skylight, so we dont get supermans lazor eyes effect going from sun in an underexposed environment.
We genrally actually want to push the 2 very close together and make the sun feel like its behind a haze soft light, then raise it from there.
Always in general, when it comes to lights, turn them off and dial them UP, dont start at a random intensity and try move around ~

Master light is always Skylight.
Child light is a potential sun.
Sub child lights are artificial lamps.
In these kind of cases, that is.
So dictating master light is always Skylight, its your base, turn everything else off, and make that look HOT. Introduce the Sun. etc --->
There is a fixed hirachy and you trim UP not down, to this hirachy, in all cases.
This way you add the light layers in a preictable non-destructive fashion where you would end out with something that looks very OFF. It is impossible if you honor the hirachy.

Also, I would not use any kind of fancy lights, keep it simple.
- Skydome with a hint of blue. No portals realy needed. ( they optimized skylight greatly recently )
- Direct light hint of yellow

I would not use any build in or physical sky models, but thats just me, I like simple stuff the less that moves the fewer things can go wrong, the easier and simpler it is to tweak.

The angle of the sun is also very important, long nice very long shadows often looks great, the longer the more yellow and so forth, soft edges. The sun has to be tamed, so start out with zero intensity and push it up gradually until it clicks in with the skylight.

Also consider to aviod shooting camera shots with the sun in the back of your neck. Then rather remove it. You just can't visually make a flash light look great, you can make it flash light'ish and thats cool, fine fine, but it wont pop anything than INFO, use it to paint art.
Blitz light is same, used for registration, no blitz image has apealing shadows.
Crazy cool from the side shadows makes everyone tear down the room jumping around all pumped up.
It's needed to manipulate for each shot unless you can get your camera in places where composition is apealing and a fixed sun does not render as a blitz.

[jnvfxartist]

So would you recommend I light my scene in this order?

1. Master Skydome that serves to fill both the interior and exterior with lots of light

2. Lamps that are meant to serve as proxies for lightbulbs/fluorescents

3. Distance sun which is just barely visible in the final render.

Also, no more placing arnold quad lights behind the windows? Let the Skydome do the work instead?

Edit: Maybe it's because I don't have the most powerful CPU but my computer struggles hard when I try to light the interior with just a skydome. Using the quads and placing them behind the window puts less stress on my system and can better deal with the noise.

For reference, I used the same Render settings for both, but the Skydome light is massively way behind in image quality vs the quad lights.

[madsd]

Then use the quad lights.
Do note you can crank skylight samples up on the light it self to get improved quality at same speed as in old days.
But if your system struggles, do the quads for sure. I just don\t have this problem.

[madsd]

Another aspect of optimizing for speed.
Use the 2 denoisers at your advantage, you don\t need a 100% clean render to get a clean image, the noice.exe denoiser is very powerful for finals, the OptiX works very good for lookdev * and finals for some cases *

[jnvfxartist]

Oh wow, you're right. Cranking up the skydome samples helps clean up the noise better. Without it, it's pretty much unusable for interior scenes. The Arnold documentation should be updated to mention this.

https://i.imgur.com/2WarGKH.png

Edit: However, I must still point out, the skydome samples only help in the areas that are exposed to light. The ceiling remains just as noisey whereas the quad lights manages to clean the entire room.

Of course, anyone who wants to use the skydome light can still do it. I'm just bringing up my experience with it.

https://i.imgur.com/pv9ArGC.png

[CiroCardoso3v]

@Jordan Nelson

How many samples did you use? I am also in the Archviz, and like @Mads Drøschler said the the denoiser does miracles. Although it doesn't clean the AOVs.

[jnvfxartist]

@Ciro Cardoso

Are you referring to the image with the skydome lighting? I updated it to include the samples for both the light and the actual render rays/samples.

[madsd]

I just spotted one of your newer images.
Camera AA5 is a showstopper.
Dial it down and increase the individual samples that causes the noise instead. Like diffuse in this example.
You want camera AA to be as low as you can as it magnifies everything across the table and render times can take a huge blow, where a calibrated diffuse will render much faster or less noisy in same time.

[madsd]

I would also like to point out that you should try go with the Skylight if possible.
You can have several practical "glitches" using area lamps, such as the general distribution can be biased, shadows looks differently and general illumination will be geared towards the look of quad lamps illuminating the set very easily if you dont take safety precautions to place them very accuratly.
ALSO -> lets say you want to look outside, and build a couple of trees or whatever, now you need to deal with a new unlit situation out there with yet another batch of custom lamps, which all can lead to production issues or final image issues.
Just a thing to think about.
If you use the skylight, you are essentially done, you cover both interior and exterior with a single unit.
And you can sleep well knowing the illumination model is "perfect"

[aaronfross]

Yes, skydome / Physical Sky with higher samples, plus higher Diffuse samples in Render Setup, will go a long way toward fixing the noise issues. Adaptive Sampling also helps. Rendering Denoiser AOVs and post-processing the result with Denoiser (Noice) also helps.

And yes, if you have to look outside to see actual terrain / geometry rather than a backdrop / matte painting, then Physical Sky is your obvious solution. But it does get more complicated than that if you are trying to art direct the lighting. Film shoots often place gels over the windows... you can simulate this by lighting the outdoors separately from indoors. Light exclusion is per object in the Arnold Properties modifier.

The important thing to think about if you *DO* use area lights to simulate ambient light from the sky... intensity decay. In the real world, there's going to be almost no decay of light across the short distance of an interior space. If you place an Area light right outside the window, you're going to get massive decay from the position of the window to the other side of the space. The area near the window will be overexposed and the room will be too dark.

Your options here are limited. You can reduce the Spread of the Area light, reducing decay, but this causes the light to be more directional. You can move the Area light very far away from the window and increase its size. Both size and distance need to be in the realm of tens of meters. But then you get sampling issues again, just like with the skydome.

My experience is that the Area light solution is most viable in the context of image based lighting... if you're using a texture on that area light, and you want the color and pattern from that texture. A big, distant Area light with a texture and a high Spread gives a decent approximation of environmental ambient light coming from the exterior.