Tips to speed up the rendering of an outdoor scene?

[Karol.Osinski]

Hey everyone, I have a little problem with the rendering times of the scene I am currently working on. I attached one of the frames.
Render settings:
Max subdivs 48
Treshold 0.008
Render region 26x26 with HilbertCurve
GI : 2x BF with 3 bounces for Secondary BF

Scene size is just 200mb.

Render time: 6 hours per frame using i9 7900X, although for this night I wanna render with all four of our i9 7900X and hope that there won't be any problems with DR and proxies.

I already changed the plants opacity to Clip and will probably do BF + LC this night.


P.S I know, despite the render times it is still looks crap - it is my 4th month in ArchViz.

Thanks in advance and have a good evening everybody.

Do you have any tips how can I improve the render times any futher

[Neilg]

Max subdivisions at 48 is way too high for that scene, drop it to 16 and climb from there with the aid of the sampler element.
you have to use bf/lc, bf/bf is a waste of time.
your render region is incredibly small and thats a slow filter - make it 64x64 if you plan to use that filter.

that should be a 15-20min render, max, on an i9.

[MANUEL_MOUSIOL]

Since you can't look inside the building as far as I can see I'm not sure if you even need the second gi pass. Maybe not even the first... Test it out and see if there is any difference. Most of the light might bounce into nothing...

[Karol.Osinski]

your render region is incredibly small and thats a slow filter - make it 64x64 if you plan to use that filter.

that should be a 15-20min render, max, on an i9.

I should have mentioned that the resolution is 3508 x 2480. The reason of the bucket size was that I indeed forget to change it from 56 x 56 (26x26 I used for half resolution), and that size I got from some forum where someone suggested a formula of width x 1.6 / 100 for an optimized bucket size + usage of Hilbert Curve sequence type. Neilg, by slow filter do you mean a Hilbert Curve right? In fact idk why I blindly followed that forum suggestion since the documentation states to just leave it as Triangulation…

Thanks for the answers guys I am gonna give it a try today and post the results later! Have a great day!

[Karol.Osinski]

Frame no. 3
Changed max subdivis to 16,
Render region to 64 with Triangulation sequence method
BF + LC 1500 subdivs

Render time: 1h 40 min. on 2x i9 7900x + W 2150B (12core iMacPro).

Is it normal?

[MANUEL_MOUSIOL]

Did you see if there is any difference between no gi and with gi?

[Neilg]

usage of Hilbert Curve sequence type. Neilg, by slow filter do you mean a Hilbert Curve right?

Ha, I got mixed up and thought hilbert curve was an AA filter. Using an AA filter with a super small bucket size slows it down. Nevermind...


Your newest result is still slow, i'm surprised you didnt get more of a speed up - at this point it has to be the lighting or materials. Are the leaves using SSS materials, or simple 2-sided ones?

Standard process to find out what's tripping you up is to eliminate things - Put a grey override material on the scene and check a render with no materials. Then disable all the lights and add a sun/sky - check with no materials, then with them. You should have a pretty good idea after that if it's materials or lights. Once you know it's one of those, you can continue to eliminate things - turning on only half the lights, using override exclude to bring some materials back etc.
You may have refractive gi caustics turned on - and if your lights are built into a housing in a 'correct' way, you're lighting the entire scene with caustics instead of direct lighting. That can be made more efficient and faked if you still need it like that. The glass material might also be contributing. Maybe you are using mesh lights with a ton of geometry subdivisions. Lots of things it could be.


Basically - make a copy of the scene and spend some time ripping it apart. Keep all the settings the same at low res so you can write down the render times and at some point you'll find the culprit presents itself to you.

[MANUEL_MOUSIOL]

What neilg said.... Too

[Karol.Osinski]

Thank you very much guys. I am gonna check all those things and do some testings as soon as I have some free time (lol)…

[Neilg]

Don't fall into the trap of not having enough time to solve problems - half an hour invested now will save you a lot more than half an hour down the road.
Everyone in 3d does it, it's a universal thing - it's easy to think of detours like this as wasted time but they're very much part of the job.

[Karol.Osinski]

Damnit I totally forgot about this topic. That project seemed like it will never end. However I did manage to cut the render times with your tips guys.
1. It turned out the biggest was the tree line on the side of the house, they were done with 2 sided material and it was the opacity which was slow to compute. I changed the type from Stochastic to Clip and in V-Ray override tab I changed the max material transcluency to something like 20 (from 50).
2.I excluded the curtains from GI
3. Obviously increased the bucket size to 64.
4. I ended up creating a mask for all the trees just to be able to reuse them with endless iterations and updates of this project.
5. Last big factor was a the scene being dark and V-Ray seems to always struggle with shadow areas so I lit the scene a bit more, changing the sun angle as well.

Render times went down to something like 40min - 1.2h on a single i9 7900X.

Cheers guys!

[damaggio]

Glad you found a work around, when you know how to optimize a scene from the very beginning is very easy to keep a render time to a short amount , Vray Next is very fast now .

[squintnic]

still too slow.
try default settings a lot of the things you are fiddling with are not really necessary