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/
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.
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
Post your scene ? Or you don’t want any “faking solution” ?
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
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/7p056pd799ypod9/shot\_161127\_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.
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.
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?
This is what i get without denoiser.
This is without curtains
This is with curtains excluded from shadow casting of light portal
The same as above, but using VrayOverride material and in GI slot - simple VrayMaterial with VRayColor in opacity slot
Last one is the cleanest image and is just slightly noisier than example without curtains.
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
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 ?
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
By checking your scene in VRay looks like you do not understand how VRay works. My advice is to read manual, check tutorials and after that return for testing.
You are totally right. ChaosGroup moves towards that direction, though i am not sure that is niche that they want to dominate in. They want to be attractive in that field, but definitely not dominate, as they will need to make another product - VRay for architects
if we look into small company of corona… the guys there release every week at least 2 videos to their channel!
chaos group came with new options.. new adaptive engine… lots of options.. come on guys (chaos group)! release video tutorials to your users!! show them how to deal with things.. i talked to many corona user that even dont know that vray is now auto subdive!!
chaos group didnt release videos to show the user the way how to use the power of vray! its not good and its make many user to see the channel of corona and heyy they talk about any options there …
for example .. now i want video of chaos group that can show me how to handle animation with brute force and light cache… nothing… nada… thats not good guys…
and i already told them that 
i use to think like that too but now i got full of flickering from light cache… i guess i need to bake the light cache
Yes, try to bake it with “use camera path” or render frame by frame with higher values for subdivs and retrace (like 6-7-8).
