I have also flickering problem, but in my case, I think it’s the reflections. I’m using built in V-Ray tempered glass material and it seems to render every frame a bit in a walk through animation. The light and the reflections are coming from high re HDR-mapped domelight.
It’s likely the HDR has too high values for reflections.
It’s not uncommon to have HDRs with values in the tens of thousands floats (or more. We’ve seen some in the *million* float. And one even at +inf.), which while helpful for GI, are the principal culprit for fireflies.
You can very quickly check this inside max, if you can’t reliably clamp the HDR elsewhere.
*) Make your current dome only affect diffuse.
*) Make a copy of it, make it only affect specular and reflections.
*) Make a new vrayCompTex, set its mode to “Minimum”.
*) In slot A put a copy of your HDR map, in slot B a vrayColor map, set to white, with the RGB multiplier set to something like 1000.0. <--- This is how one clamps an image to 1000.0 float from inside max. It doesn’t *scale*, so it’ll lose the hue of the values above the clamp level, and produce white.
*) Put the vrayCompTex in the dome affecting reflections and specular.
*) Render.
If the fireflies are gone, you’re golden. 
Notice this *will* change the look of reflections and specular highlights, sometimes more, sometimes less, depending on what are the HDR contents.
It will also avoid fireflies, however, in the vast majority of cases.
Thanks a lot Lele,
Actually I’m not seeing fireflies. The problem is seen on planar glass. The reflection is not image, its a color, which changes in every frame making the glass flicker. Curved glass is working fine with reflections.
Clamping may help regardless, have you tried it?
p.s.: shouldn’t it help, please share the offending piece of scene and the HDR with support, and we’ll look into it.
I have not tried clamping. In fact, I don’t know where to do that in animation.
I have explained it above.
Animation should pose no problem, be it camera, geo or lighting.
Feel free to send me a part of the offending scene, i’ll set it up for you.
OK, I see it now. I created the lights as suggested. On still image rendering I don’t see slightest difference. I will put this to rendering queue and see what happens with the flickering in animation.
Just out of interest, does your glass have ‘reflect on back side’ ticked?
There is an issue I just re-posted about, that has existed for a very long time.
Maybe this is similar so thought to mention it. Sorry if not.
I tested the suggested set-up and flickering became even worse. I try next rendering without HDRI map.
Reflect on back sides is not ticked; I’m using the tempered glass from built in library. Should I try another.
I find this very odd.
Reflect on back sides is not ticked; I’m using the tempered glass from built in library. Should I try another.
The glass preset is a very valid shader, nothing strange about it.
I’d think we’d need a piece of the scene to figure it out, the possibilities are endless.
Thanks again Lele,
I have one idea. My audience doesn’t like perspective very much so I often render with orthographic camera - this animation being one of those. This might explain why the reflection changes so much between the frames when moving the camera. I switched back to default camera with 105 mm lens setting. I’ll let you know if this is better and if it is, I might test shortening the Focal length even more.