noisy enviroment fog

[leabum]

I want to render volumetrics and therefore created a extra renderlayer with black surfaceshader on everything.
My lights mainly consist of mesh lights and rect light and an HDR. The hdrs subdivs are set to 128 as well as the meshlights subdivs in the region I am currently testrendering.
The treshold of the DMC and Imagesampler are set to 0.01 both and Max Subdivs to 50 with Min Shading Rate of 100. The enviroment fog has subdivs of 128 as well with fog distance of 50000 and stepsize of just 1. Shouldn't there be enough samples? The result is okay but not 100% noise free. Esspecially cranking up the AA samples helped, whereas changing the lightsamples did't have that big of an effect. Isn't Max Subdiv of 50 high enough? Thank you!

[leabum]

okay I decreased the AA threshold even more and lowered the other parameters again and the result is getting better. Still not 100% noisefree. Is it right that the Enviromentfog needs so many AA samples?
Obviousely the rendertimes are very high now. Is there a way to use the areal perspective without vray sun or a different and faster method to get something like a volumetric bloom effect around lights?

[svetlozar.draganov]

A very quick and effective way to add bloom effects around the lights are Lens Effects.
Those effects are applied on post and they add no additional time to the current render times.

Environment Fog would be needed if you would like to render areal perspective effect or volumetric lights. Those effects are not very cheap in term of render times and their calculation depends on scene setup and complexity. May you attach the scene or a part of it so we could check if there is a way to optimize it even further?

[leabum]

Yeah, it is supposed to look like it just rained and there and the lights are catched in by the particles in the air. So not necessarily a typical lens effect. I tried to use the denoiser but it creates some kind of artifacts. Otherwise getting it noisefree seems only be possible with a very low AA threshold and high max subdivs, while adding 20 Min Shading Rate helps quiet a bit. Here you can get the file, I would appreciate any advices. https://www.dropbox.com/s/48tfrvm3zv...etrics.mb?dl=0

(textures are missing obviously, just concentrate on the volumetrics renderlayer. Maya 2016)

[Komposer]

hi...I made some tests with your scene and set the focus to only the 3 downlights in the front! (switch off all other lights and meshlights)
Set the image sampler settings to classical "use local subdivs" !!!! (the "new way" never helped me to archive better or faster results!!!)
Testet many different settings while using the original meshlights - nothing helps, not possible for me to archive better results.
Then I set 3 new Rectlights at the bottom position of the original meshes (same temperature, Watts - 0.2 intense!!! - your meshlights have 150 Watts!)
The rendertime shrinks fom 9min43 (very bad result) to 2min30 (much better result).
See the attached images...
It seem to be not possible to archive good fog-results with mesh lights!!!! (Or chaos??)
I hope it helps a bit.
BTW, when rendering fog, you need minimum 2 subdivs, otherwise you get black tiles!
BTW2, the meshlights renders errors - don´t know why...

[leabum]

Thanks, I will replace the meshlights for this renderlayer. Yeah I also tried the use local subdivs approach first but had no luck as well. Then I tought I let vray figure out what the best values are. Thanks for the worksround.