I know there was talk about improvement, but I think things are getting worse. I am getting some awful noise when using an HDRI in my V-Ray SkyDome. There has always been more noise to clean, but as of lately, it is 2-3 hours to get an image that is pretty noisy still. I haven’t changed my workflow.
Not all HDRI’s are equal. Is your workflow BF/LC, auto sampling, denoise?
I buy the best ones I can find, mostly from location.com. Yes, BF+LC with denoise and auto sampling.
Hmm. For exteriors I’m using AA 1/12 or 1/16 with a threshold of 0.01 and MSR of 6 or 12. Super clean even before denoising. Interiors can be noisy depending on how much of your HDRI gets in through openings. GI is usually the culprit of the noise which I boost the MSR to 24-32
Man, I haven’t messed with setting in a year. I can still control the MSR, even when I am using Auto Sampling, correct? I thought about this last night, but I though I remember Vlado saying it wouldn’t change anything.
Is the sun still in the HDR? Sometime it helps to paint it out and add a direct light or VRaySun instead.
Yes, the sun is there. I’ll try that and see if it helps. Thanks!
No problem!
For lighting (not sharp reflections) it helps to blur and scale down the HDR to say 256x126 for example. Might work with setting the VRayLight resolution lower as well but haven’t tried to see if it’s the same result. This will reduce noise with usually the same look as sky lighting/GI tends to be very blurred in general anyway. I usually paint out the sun and replace with a directional light.
Tried lower res hdri but the same result.
If you’re using the map in the environment slot the try using it in a VRay light instead. And it also looks like the sun is still in the HDR image, painting it out and replacing it with a directional light should help.
I use it in a dome light. I have a forest hdri which has several areas of bright light, but that’s what I like about it 
so that’s the problem
You could clamp the bright areas down. Using the vray comp tex in minimum mode and a vray color which is giving the maximum color. So you won’t need to paint them out. (can get pretty tricky if you have many of them)
Then add a sun to get directonality and high energy light back. That should help a lot with the noise.