Specs flicking during a shot

[luan_simonin]

Hi, for a project I'm rendering a shot with a creature. It's in a layer of it's own, and during the shot the specs on the creature flick almost every second frame in a few spots (eyes and side of the jaw). I've checked the rawlighting AOV and the lights stay consistent there, so I'm assuming it's directly to do with the specular. It's also interesting that I've already rendered other shots of this same creature without any issues of that sort, it's really just happening on this one shot. Has anyone ever encountered this issue before?

[Dubbie99]

We had it come up on a job. We tried everything we could think of to solve it to no avail. We were rushing for a deadline at the time and didn't have time to work with support.

[viktor_angelov]

Hi luan_simonin Thank you for contacting us! Is this the only geometry the issue flickering appears with? What V-Ray build and Houdini version are you using?

Could you share the scene with us so we can investigate further ( V-Ray > Pack Scene ) You can send us the files here or by Submitting a request to our system.

[luan_simonin]

Dubbie99 That's so unfortunate... I'm also on a somewhat tight deadline for this shot, so I hope that the problem will be solved in time. If a fix is found, I will forward it to you!

Hi viktor_angelov , I've submitted a ticket, thanks!

[Joelaff]

Sounds like fireflies. If it lights have a lot of directionality to them (or you are using a VRaySun) try reducing the directionality.

You can duplicate your light and disable specular for the original, directional version, and disable diffuse, etc for the duplicated light. Then reduce the directionality of this duplicate.

Raising Min AA may help as well, of course. The Intel denoiser can also sometimes help, if you can tolerate it.

[viktor_angelov]

luan_simonin Thank you for the files, we have received them. I will take a look and let you know what we find.

[luan_simonin]

Hi Joelaff, I'm aware of what fireflies are, but this seems way too big to be it, right? (see video attached). My lights are also fairly diffused, and I don't think it's a matter of denoising. I will still try to separate my lights and give it a go, thanks for the suggestion.

[Joelaff]

As you say, that doesn’t look like fireflies. Do you have two lights touching or overlapping at all? Do you have any overlapping geo in the eye that could be doing it? Also check the shadow bias perhaps.

Also, I have seen some bugs, at least with standalone, where render elements can cause some weirdness like this. (They have either been reported, or I can no longer reproduce.)

I am sure support will figure it out.

[tobiasroesli]

Hi luan_simonin, I just read your post and I was thinking that maybe one or more rendernodes don't have OCIO or something like that enabled. Or textures which are locally and not on a network path or something like that?

I mean, that only is a possibility if you're using rendernodes

[luan_simonin]

Joelaff Thank you so so much, I had 2 lights that were overlapping which was actually what was causing the issue! I moved one of them ever so slightly and now it renders just fine. Now that I'm writing it it makes complete sense why it would be an issue, but it didn't cross my mind somehow. I'll make sure to never do that again! Also, thank you to everyone who interacted with this thread and tried to help.
Best,
Luan

[Joelaff]

Glad it helped. I have gotten a lot of random errors if VRay lights touch each other at all. Usually if they just touch a little bit it is OK, but I have had two rectangle lights just touching their corners cause issues such as this. A lot of time just making the lights invisible helps, but safest just to avoid any light to light contact.