V-ray Next 4.30.02 - Extreme "dancing" white pixels on any material at a distance with glossy reflections

[^Lele^]

Your AA at 1-6 is way too low.
Your LC subdivs should be at least 3000, with a retrace of at least 8.

Reset the settings to their default, select the bucket sampler, set min AA to 3 or more (so it'll find the detail), select the LC preset named "Animation" (or follow the guidelines above), and render with motion blur to get the correct result.

V-Ray is doing it right, in this case.
The longer the blur length, the smoother the transitions of highlights across the discontinuous geometry will look.
If you render without motion blur, there is no correlation between frames (and your camera is trucking in, ensuring angles change at each frame, for all pixels.), and with a highly discontinuous surface like the bonnet and various glasses, this behaviour is wholly expected, and entirely correct.

If you prefer to kill the highlights, a-la Corona, feel free to turn on SPM and lower burn to some very low value.
It will not help here, however.

The reason has to do with shaders setup: make those glasses (Multi-sub, ID 5) something like 0.8 gloss: at this distance no difference will be perceivable anyway, but thew broader gloss tracing cone will smooth the transitions of the highlight.
Likewise, there is no need to set a reflection color to white.
The same applies to the headlights reflectors and glasses (those too catch a glint. again, it's the correct thing to do for V-Ray.), ensure they aren't total reflectors (no fresnel, no gloss in yours), or once the angle is right, they'll shoot the sunlight back at you (think a hung mirror turning in the wind, far in the distance. That's what's happening here.)

Attached, four videos (not denoised):
a) a video of the sequence rendered like suggested above,with motion blur at defaults, but without any clamping of the highlights or changing shaders.
b) No motion blur, but with a Reinhard burn of 0.01 and SPM activated.
Both still exhibit discontinuities.
c) I lowered gloss marginally on the windows glasses, and on the headlights chrome reflectors and glasses for the blue car (I haven't changed all the shaders accordingly, so something still glints. I'm sure you get the gist.).
You'll notice that is the most coherent so far.
d) Lowered gloss for shaders and motion blur with a length of 1 frame. Glinting is reduced to nothing at all for the shaders i changed.
I didn't compress highlights for the last two videos.

As a side note, i am *very* interested in studying the Corona version of this scene which managed frame-by-frame continuity by simply rolling the highlights intensity back.
I'd be grateful if you shared that one as well.

[Spatial]

Hi Joelaff, great suggestions. We had considered using 2 suns moving forward but was hoping for v-ray to just...work. To simplify procedures for all staff. You know what its like, someone updates the traffic xref because of a client comment right before renders and in the rush the new cars don't get added to the include and exclude lists in the suns. Nightmare.

I had also considered creating distance blends for glossy materials that reduces the gloss amount by x when the camera was y distance away, but this is a bit of a library overhaul and who has time for that.

The 2 sun hack might have to be the way to go for now until V-ray can catch up to Corona though :/

Maybe our studio which outputs a huge number of high fly through videos in giant infrastructure projects tends to get this hot pixels issue more frequently than others who tend to do closer, smaller scenes. I don't know. But we're usually working in many km's of project space and usually flying high above which is when this problem presents itself the most.

I have definitely tried cranking subdivs. I even went up to 24/24 and the giant 4 pixel square white hot highlights were not subdued even a little bit.
on a side note 2/16 is too much overhead on our average 3000 to 5000 frame outputs. That would get very expensive very fast.

I will try the soften image filter and see how that goes! thanks for the suggestion!
Hopefully a more permanent solution under the hood is on the cards. Talk to the Corona devs! They fixed it

[Joelaff]

Thanks for the reply Aleksandar.

Sun size to 100 creates ultra soft shadows so it's not a tenable solution.
Unless you have another hack that allows a massive sun size but retains sharp shadows?

The link you provided has the same old suggestions that I outlined in my initial post and I have never been able to get them to work.
If you can get those tips to work on the test scene I provided, I'll be extremely happy to be wrong.

Hopefully support can take a longer look as this happens to us in nearly every single project and it has been very frustrating for a very long time.

Corona nailed it with its highlight suppression setting. Is v-ray just not capable of handling this?

You could use two VRaySuns. One affecting only specular which is large. The other affecting everything else which is small.

Also, depending on the severity this may help or not, but it makes the best dang looking tiny specular highlights, and that is to use the Soften Image filter around 2.98-3.98.

Also increasing minimum subdivs (2-16) usually helps tremendously.

[Spatial]

Thanks for the reply Aleksandar.

Sun size to 100 creates ultra soft shadows so it's not a tenable solution.
Unless you have another hack that allows a massive sun size but retains sharp shadows?

The link you provided has the same old suggestions that I outlined in my initial post and I have never been able to get them to work.
If you can get those tips to work on the test scene I provided, I'll be extremely happy to be wrong.

Hopefully support can take a longer look as this happens to us in nearly every single project and it has been very frustrating for a very long time.

Corona nailed it with its highlight suppression setting. Is v-ray just not capable of handling this?

[hermit.crab]

This topic has some tips about similar issues. Another thing that significantly reduces the fireflies is increasing the Sun Disc size through the Size multiplier ( a high value like 100 seems to eliminate them completely on your scene without a drastic lighting change).

[Spatial]

800% zoom in showing issue:




This one has plagued our studio for years and we've always solved it just by turning off v-ray sun specular.

This primarily happens with our car materials and any material that has a glossy value above 0.8 or more where the meshes are quite some distance from the camera in sub-pixel land.

I have methodically tried every single v-ray setting under the hood (have searched extensively through the forums) and nothing prevents these bright white pixels from occurring except for two things:

1.) turning off sun specular (sun is always set to invisible by the way)
2.) turning off or lowering gloss or reflection amounts on materials. (even this can just cause softer dancing hotspots)

Annoyingly, I installed Corona as a test and it has a simple highlight compression setting that when set to 1.0 instantly solved the problem!

I cannot find the equivalent setting in v-ray if it exists.
I have tried every combination of color mapping, clamping, burn values, sub pixel mapping, color mapping types...and on and on...literally cranking, lowering, checking or unchecking every single setting possible in v-ray

I have uploaded the above simple test scene here:
https://tinyurl.com/y5mbw4qc

Any insight would be greatly appreciated.

Thanks,
KG