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

[jeremiah_jones]

Hi Guys, newbie here (don't know if this is the right place to ask this question below)

CLAMP OUTPUT QUESTION: -guys, how to unhide CLAMP OUTPUT in Vray 5 render settings (3DS Max) using a maxscript?
(it's hidden by default says chaosgroup -for I have problem with jagged edges on bright area of an object (it's easily solve before by SubPixel Mapping and Clamp Output)

I'm looking for the same thing here. How do I access this maxscript so I can see the clamp output settings?

[lassysilvestre]

Hi Guys, newbie here (don't know if this is the right place to ask this question below)

CLAMP OUTPUT QUESTION: -guys, how to unhide CLAMP OUTPUT in Vray 5 render settings (3DS Max) using a maxscript?
(it's hidden by default says chaosgroup -for I have problem with jagged edges on bright area of an object (it's easily solve before by SubPixel Mapping and Clamp Output)

[^Lele^]

It won't make bloom and glare impossible, not to worry.
Thresholds may have to be adjusted a bit depending on the specific situation, but it will leave overbrights in the scene, so that all that stuff will work fine.
I haven't experimented with the tech enough to give you a general rule of thumb for what happens to values.
vlado will know.

[seandunderdale]

What are you ping / highlight values once you've gotten a result you're happy with? Anything in compositing (or vray glare glow) that needs values above 1.0 always suffer when clamping is applied. Do you find you dont need those values and anything that might need them can just be eyeballed and approximated just as well?

[Spatial]

Wow, that's very promising and awesome to hear that this issue is already being addressed and working in builds.
It is hard to roll out an indeterminate version to the whole team like this and keep the pipeline reliable.
We haven't moved to 5 yet so it would be good to know how where this build sits in relation to our 4.30.02 build 00001 installs.

I wonder what the roadmap looks like seeing this in official releases as we get this issue nearly every project we do.

Thanks heaps for the update Lele. I will keep this build handy in a pinch.

[Joelaff]

Great to see some progress on this.

[^Lele^]

This is rendered from the original file, without any modification (besides turning off denoising, and setting the output to an EXR), with the fireflies suppressor build mentioned before.
Renders were below 5 secs per frame.

This is the internal build, should you want to try it, for max 2020.
A few caveats apply:
a) This is from well before the release of v5. It should be used *exclusively* to try out the firefly suppression qualities in scenes which were problematic.
b) It *requires the bucket sampler*. And more than one AA Sample (as usual, defaults will serve you well.)
c) It should be representative of speed for the firefly suppressor only.
d) The feature is always on in the build, if you use buckets. Install in place of the old one, switch to bucket sampler, render away.
To compare render times and looks, simply switch to the progressive sampler.

If a build is needed for another max version, Vlado would be kind enough to make you one.

[^Lele^]

Sure, open a ticket if you want, i'm not gatekeeping, i'm merely helping to sort out the amount of data the forum produces for busy coders.
Either way, this is no news, work's been going on on this for a long while, now.

[Spatial]

Yeah 0 is the default which = highlight clamping off.
The higher you go you eventually reach fully unclamped again though, so somewhere in the middle gives a really sweet result with no artifacts. It's a beautiful thing.

Cheers Lele, I might put a ticket in anyway. Hoping the forum would help, but this is just something v-ray needs to be better at under the hood I think.

[^Lele^]

The statement is correct if you set clamping to 0, ofc.
EDIT: not even. 0 is a special value which renders unbiased, reading the manual. But it's clearly not so. Things have changed from what's written in the helpdesk.
I may sound testy, but i always flag stuff, even if i personally don't like the approach, to the relevant people (which ain't support, here.).
You are being read.

[Spatial]

That is an incorrect statement.

Its just clamping the highlights from peaking out way past acceptable ranges before it gets to the frame buffer.
I just read up a little Corona documentation and my theory was right about that.

The highlights are still there. They're just not insane

I've since done a range of tests with highlight clamping values. 1.0 is pretty extreme in the first test. (still infinitely better than the alternative and close-ups of materials still look beautiful with just the smallest of pixel highlights being clamped out:

Example: (middle click to compare in browser tabs)
Highlight clamping = 0
Highlight clamping = 1

It gets really interesting when you set the highlight clamping value quite high.

Check out what a value of 100 does:



This is it! That's the holy grail right there. A visible specular highlight that is smooth and looks great. No crazy pixelly dancing firefly shenanigans or white hot pixels that flicker on and off constantly. No insanely high settings and long render times required to fix it. Just works.

Avoiding this like the plague is a bit silly. This option is in Corona to fix a very long standing problem and it does it spectacularly.

Please let this be the same tech you are talking about in the nightlies and not the "highlight killer" you are describing.

side note: do I need to actually make a formal support request or are support actually looking at this?

[^Lele^]

Eh, it entirely kills highlights, basically turning your shaders to diffuse.
If you like this, your best bet is to wait for our version of a similar tech (there should be a build lurking somewhere in the max 5 beta forums.).
I would stay away from this like if it was the plague, because those highlights *need* to be there, in one form or the other, to marry those parts with the rest of the scene, but i can see the usefulness if you're pressed for time.

[Spatial]

Thanks for the response Ali, unfortunately i have already tested those values and they do not change anything with this issue.

Wow Lele, thanks for such a detailed response with test cases and videos! I really appreciate the help.
AA makes no difference to this issue. I've cranked min and max subdivs to astronomical levels as well as increased LC subdivs to very little effect.

Lowering burn has a far different effect to Corona's fix which appears to leave the image completely intact while only removing hot pixels. It's a bit of magic I wish v-ray had. This whole thing also keeps us away from glare and bloom which only makes this problem even more in your face.

I know reducing gloss and reflection helps this issue but that's a huge task. We also have quite a few forest pack packs that exhibit this behavior with leaf spec and gloss and its prohibitive to go changing all those libraries too.

As far as I can tell after years of dealing with this one, is that while v-ray is being "entirely correct" it's mostly being in the category of entirely unwanted and completely undesirable which is the last thing a busy studio needs.


As requested, here is the Corona test case on the same scene.

01.) - Corona also renders it the same "correct" way by default with sparkly highlights




02.) - Highlight clamping value in the system settings



03.) - Clean as a whistle



These are 15 second frames showing that high AA settings are not required, plus i didn't have to go changing all the materials in our prop libraries

Corona Scene: Onedrive link

Maybe switching to Corona is the answer but that's a whole other kettle of fish and would be like trying to turn the titanic during a busy production schedule.
I just hope Chaos can do something similar to Corona instead of asking the customer to change years worth of materials and libraries.

The only quick fix at this stage seems to be the 2 sun method(One sized at 100 but only affecting specular contribution) + some attention to detail in scene management.
Even if v-ray sun had some sort of option to disable this flickery pin-point specular behaviour or something. Or a mega v-ray sun that retains hard shadows by default haha.

Thanks for all the help so far!

[Joelaff]

Maybe you could try to decrease the Max ray intensity with subpixel mapping checked or with the clamp output to 0.95, it will darken the scene a little bit but it will reduce the hot spots

Is this what corona is doing? Or do they do something different?

[Ali Essawy]

Maybe you could try to decrease the Max ray intensity with subpixel mapping checked or with the clamp output to 0.95, it will darken the scene a little bit but it will reduce the hot spots