Help with banding issue in fog...
 

Hey guys I am wondering if anyone can assist...

I am doing an underwater scene in Maya using Mental Ray with Maya's Physical (water) fog.

I am getting banding in the water environment fog. I have tried everything I can think of in Maya and googled and search but coming up short on how to solve this issue.

The link will hopefully show what I am getting...appreciate any help...tia.

http://dragonflystudioproductions.com/fogbands.jpg

Hi Dabu, I moved your first post on the forum as soon as it came up on the site as it belongs here in the mental ray section, and I just noticed you posted it here as well now. Please don't double post on the forum as all lounges get viewed and post only once in the section which is relevant to the question.

I don't know the answer to your problem but I'll have a dig in my mental ray archives and see if I can come up with something useful. hopefully someone else can offer some help as well.

Thanks,
Nilla

Sorry you might not have double posted I just noticed it could be a system error making it repeat but I just wanted to mention it in case because it appeared twice on the front page:)

Thanks for the move Nilla...I assumed since I am a Maya newb it should go in the newbie section.

And yep I didn't double post. NP either way though. I understand.

And thanks for taking the time to consider the question...

I'd make the same assumtion I think a lot of people do that's why I've been moving threads around from there. I'm gonna try and make the description a bit better for what should go in there because it's not clear and as I normally search forums myself when I'm stuck I know it's easier to find answers if they're where you expect them to be.

I'd say you're doing pretty well for a newbie:) that image looks really nice to me so far I like the water. I've never used the node you're working with which is why I can't help but I render a lot in mr so I might be able to figure out where to find some info on it. You can get some strange results especially with final gather and banding artifacts when you have your quality settings too low a lot of the time so adjusting these in your render settings is always worth a try but it might be something in the node itself that needs adjusting. Something tells me as this is fog it's more likely the case. It does look similar to a problem I had a while back though which was fixed when color corrected and increased quality I seem to remember, so take a look at your render settings.

What is your output format? It looks like the image went through some pretty brutal compression.

Thanks again....

I'm outputting HD1080 Maya IFF....I compressed in photoshop to make the image easier to upload and view...

I tried the MR quality at 16bit...but didn't see an improvement over 4 bit minimum 16bit max...

I'm trying to mess with the settings in the environmentfogShape1 node...it seems to make somewhat of difference...but as of yet still can't get rid of the bands....I'll keep trying.

Appreciate it...

Nope...I was hoping it may have controlled the fog resolution...:( oh well...

so close....lol.

Did you find an answer to the problem somewhere yet? I read up a bit on physical fog, and I can't really think of what in the node itself would cause the banding pattern. You try a volumetric mental ray material for fog instead, but that's not really the correct fix to the problem:)

Another thing that struck me is that you might be able to get some help on a site called CG Architect if you posted it there, your scene is an exterior and they have a lot of arch viz professionals that give you some good anwers. Most people on there use max and vray, but there's a lot of mental ray and a bit of maya so someone there might know what it is straight away.

Nilla

Thanks Nilla,

No solution yet...although I found a weird way to duplicate the problem using Maya Software render lol...

And a weird thing happened on a movie rendered out of Shake with a Maya Software render....The image sequence looked fine in Shake.

When I exported the movie out of Shake and opened it in QT 7, the fog layer was gone lol. Closed and opened it again in QT7 and the fog layer appeared after a second.

Interesting...something funny about the environment fog and perhaps something corrupted on my system...

I will however try your suggestion and see if I have any luck...I was hoping it may have been a setting I missed...with a common solution.

Will try some Maya maintenance, or a re-install if no one seems to know...

K>

Try it because there's definitely a lot of people there who render with fog. It's most likely some simple setting that would fix it, usually is. If you upload your scene somewhere or e-mail it we can have a look at it as well, not sure we'd get it but it's more difficult to guess without seeing exactly what's in the scene file.

It seems to be your bit depth. I did a 8 bit and 16 .iff comparison and the fog started banding.

That still makes sense, because it looks more like a technical issue than anything else. And especially since you get it replicated. Upload the scene dabu if it doesn't work, it sounds to me like Genny should be able to fix it for you.

Wow somehow I missed your post Genny...

The bit depth makes perfect sense to me....

So here is where the newb in me is the issue....I googled for the answer but could not find it...I did however, see a lot of reference's to banding and as a photographer I understand the banding issue from 8-bit. But....

How do I change the bit depth in my MR renders? lol....

My settings are Preferences>Rendering>32-bit floating point.

MR>Quality>Framebuffer>RGBA (Short) 4X16 Bit.

I found one strange reference for creating a text file and saving it as a Maya.env with the text:

IMF_TIFF_COMPRESSION = none

And placing it in the Maya project folder and restarting....

lol...sometimes Maya seems so strange to newbs...

ack.....:help:

Can't believe I got past Expressions.....:P

Well so far no matter what settings I use in MR framebuffer quality; 16/32, or format type .iff, tiff, exr, etc....everything renders out at 8-bit...:playfull:


omg....:ninja:

Ok I didn't realize the render in Maya is 8-bit....Once I rendered a frame in Qmaster I was able to get a 16-bit image out....so Duh on my part and much thanks for the suggestion....

I still have banding but I will play with the quality settings now that I know how to get it out of Maya at a higher bit depth...

I think the problem lies in the Water Light Decay setting of the Physical Fog (Water).

Because if I set the Water Light Decay to zero...banding is not an issue...

The problem is without using the Water Light Decay I am unable to create the same underwater effect.


Here are my settings if anyone wants to see if they can get rid of banding with these settings

http://dragonflystudioproductions.com/envwater.jpg