Flickering in animations with recommended settings

[uforis]

Thanks for the tips Lele. Are there any other factors for why BFBF for interiors are ill-advised, other than render times going up? I am basically just trying to formulate an ironclad backup plan should the recommended BFLC settings produce undesirable results.

It seems in my case, calculating the high res (less flickering) LC increases the render time substantially per frame. As I mentioned, with 16 lights or so, it was taking between 5-10 minutes per frame already to produce the LC. On BFBF, I was between 1000-2000 passes already by the same point, and with mild denoising, I had a great frame before the LC would have been finished. It's a real head scratcher for me, because I can't imagine that my project is more complicated than those you've worked on in the film industry, so figuring out what's going on with the LC has been quite a run around. It must have something to do with overlapping faces or something else, which BFBF with the secondary ray bias set to your recommending 0.001 has all but eliminated as an issue (it was still an issue with my BFLC test).

Regardless, you guys have really helped me learn a lot more about VRay throughout this struggle, so I thank you both (and Slizer). The more I learn about VRay the more I love to use it!

[^Lele^]

No, other than rendertimes going up, BF is the most accurate of methods available.
If you could share the scene with me, i'd be curious to give it a whirl and try and find good settings for it.

p.s.: https://youtu.be/-DP6e9UsxtI?t=40
The whole canyon sequence is a per-frame LC plus BF.
That includes topology-varying geometry found in both the destruction and the meshed fluids.
Raindrops on the (spherical!) cockpit are animated v-ray displacement with water level.

[uforis]

Very cool.
I'll continue to use BFLC for sure, but it's great to know of a backup plan that works.

I'd be happy to package it up for you. Do you recommend using the VRay Scene exporter? Is there some guide somewhere about sharing rather large projects?

[^Lele^]

you could try the max archival function.

[jeffkrigstein]

Thank you for this thread. I was having exactly this same problem while using the recommended BF-LC settings for animation (objects and camera both moving). This thread was a big help to advise me to just use BF-BF. I honestly didn't think my scene was that complicated though; just an area light, directional light, and a piece of equipment in an open space. Gotta learn when it's most appropriate to use each GI configuration.

[JuhaHo]

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.

[^Lele^]

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.

[JuhaHo]

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.

[^Lele^]

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.

[JuhaHo]

I have not tried clamping. In fact, I don't know where to do that in animation.

[^Lele^]

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.

[JuhaHo]

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.

[fixeighted]

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.
https://forums.chaosgroup.com/forum/...by-brdf-change

Maybe this is similar so thought to mention it. Sorry if not.

[JuhaHo]

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.

[^Lele^]

I tested the suggested set-up and flickering became even worse. I try next rendering without HDRI map.

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.