curtain ans some 2 sides material... help

[oren]

i dont want any faking solution
i want to put curtain on windows (2 side material) and go render without to find that i add a full of noise to my scene

im sorry but i must to understand why corona engine can do it easily??

vray - dome light - hdri - setting bf - lc the rest is out of the box

corona - hdri on environment - setting - out of the box

its just like that or what wrong?
link to image :
https://postimg.org/image/8jifkb1sv/

[viscorbel]

Somehow I get a feeling that 2sided mtl curtains are slowing the scenes down way more than they used to.
I don't have any proof or comparisons, just a general feeling that in past they worked well and now I have to fake and cheat until getting a decent speed, even though the current pc is much faster than the ones before.

[Morne]

In a recent one I had to exlcude the curtain from casting shadows otherwise it was just too noisy and taking too long to render

[Oleg_Budeanu]

Post your scene ? Or you don't want any "faking solution" ?

[oren]

no i dont want "faking solution" i will post the simple scene and i really want to understand why other engine deal with 2 side material so well

the scene
https://we.tl/TMcsj2hg01

[Oleg_Budeanu]

can you post full resolution corona render to compare ?
Also what i see from first sight is that you are not using Simple VRay Portal. You can also enable clamp and enable subpixel mapping - that will reduce rendertime thus image will be cleaner. Also you can disable reflective and refractive caustics.
These are different renders and different approaches - this was discussed million of times, you have to have different approach when rendering with VRay - that's my opinion.
Also tell if you are using denoiser in Corona and VRay ?
This is what i got with denoiser and some tweaks https://dl.dropboxusercontent.com/s/...127_201517.png
rendertime with denoiser is 1 minute 40 secs on my weak laptop.
Yeah also it is a good idea to exclude curtains from VRayPortals, so you will have "cleaner" samples going inside.

[oren]

oleg
look at your test
its full of glitches and splotches
its better to have noise and not things like that man

denoiser ans irradiance map kill your test man

[Oleg_Budeanu]

Well this is not irradiance map, this is bruteforce with denoiser. But you wanted crystal sharp image for one minute ? You live in a dream world, mate
And yeah, show please full size corona image, i want to compare noise levels i got with corona.

[oren]

no i l know it can be sharp but i try to find the best way to create curtain without create noise... i think opacity will make more noise

what software can measure noise?

[Oleg_Budeanu]

https://dl.dropboxusercontent.com/s/...128_202642.png
This is what i get without denoiser.

This is without curtains
https://dl.dropboxusercontent.com/s/...128_202832.png

This is with curtains excluded from shadow casting of light portal
https://dl.dropboxusercontent.com/s/...128_203231.png

The same as above, but using VrayOverride material and in GI slot - simple VrayMaterial with VRayColor in opacity slot
https://dl.dropboxusercontent.com/s/...128_203627.png

Last one is the cleanest image and is just slightly noisier than example without curtains.

[FLP]

Had a very brief look at your scene.

A. I don't believe you need to use a plane light set to portal with an HDRI dome. Use a plane light or HDRI dome or Plane light set to portal with HDRI in enviroment slot.
B. There is almost no direct light as your opening is obscured by the curtain. The default progressive settings (1/100, MSR 6) are trying to solve the GI with AA.

So, lowering your max subdiv while raising your MSR will tell Vray to use a lower ratio imaging samples and greater amount of shading samples.
Try (progressive mode) AA 1/12, 0.005. MSR 28 it looks closer to Coronas noise level.

Cheers

[Oleg_Budeanu]

Had a very brief look at your scene.

A. I don't believe you need to use a plane light set to portal with an HDRI dome. Use a plane light or HDRI dome or Plane light set to portal with HDRI in enviroment slot.
B. There is almost no direct light as your opening is obscured by the curtain. The default progressive settings (1/100, MSR 6) are trying to solve the GI with AA.

So, lowering your max subdiv while raising your MSR will tell Vray to use a lower ratio imaging samples and greater amount of shading samples.
Try (progressive mode) AA 1/12, 0.005. MSR 28 it looks closer to Coronas noise level.

Cheers

Actually yes, i forgot that first thing i did is i raised MSR to 30

[LudvikKoutny]

I do not think the point here is to get down to tweaking of all sorts of parameters, but rather that Corona simply seems to handle this (in archviz quite common) case a bit better by default.

There is no reason V-Ray should not be able to handle such cases better without need to tweak settings or introduce things like denoiser to cover the problem up.

I've made very similar scene from scratch to avoid possibility of trying to debug a scene from inexperienced user who flipped some obscure switch somewhere, and yet I was able to reproduce the behavior:
This is V-Ray 3.40 with 100% defaults at 1 minute:


And this is Corona 1.5 with everything default except time limit changed from 0 to 1 minute:


The slight brightness difference is due to the slight differences in CoronaSky vs VraySky, non the less it's not nearly as much different to attribute to such performance difference.

Now, I suspect that this is related to something I've reported some time ago. Not an issue of 2sided mtl but rather that DomeLight is generally inferior to Corona's IBL when sampling deeper interior scenarios. I tested that hypothesis by removing curtains and instead narrowing down the window opening:
V-Ray 3.40:


Corona:


It is something I've already reported here: http://forums.chaosgroup.com/showthread.php?89808 but it did not get much attention. Generally, I think that the problem is the dome light by default is not sampled enough, and with universal settings + global subdivs approach, there is no way to increase for DomeLight specifically. Corona for example, has global sampling multiplier for all light sources set to 2 by default. That could be the culprit here. So maybe it would be a good idea for dome lights to be generally sampled twice more. It would not slow things down much in simple scenes, but could boost them up in cases like interiors.

Scene is attached here:2sided_Noise.zip

[Oleg_Budeanu]

To be honest i think VRay is created that way, that it has to be tweaked. I achieved the same amount of noise (1% difference i think) in my last comparison by tweaking some settings which are obvious, if you spend a bit of time to understand how VRay works.
About your idea - it may be so and i think there is always room for improvement. In thread you linked one of Chaosgroup team asked you for scene, did you send it ?

[oren]

for tons of tests in all kind of topic
its show the corona is much more cleaner in same time of render

im not talking about iraddiance map ... i always mean brute force and light cache vs path tracing and uhd cache