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JLopezVFX
12-30-2011, 12:41 PM
How do you remove banding in Mental Ray renders?
I'm rendering at 16bit half / OpenEXR
No G.I. / final gather


https://lh3.googleusercontent.com/-Je44xZGzFRg/Tv2wqw3eWlI/AAAAAAAACqg/18CdP6fpQrI/s960/Banding%252520Render.jpeg

Please Help,
Thank you.

beaker
12-30-2011, 07:34 PM
If your already rendering at 16 bit float, then a good chance it is just your monitor. Remember that your monitor is typically only 6 or 8 bit. So the file format can store many more levels of color then your monitor can actually display.

Bitter
12-30-2011, 11:52 PM
Also be sure the file type in your render view is set to 32-bit in Maya (requires restart)

JLopezVFX
12-31-2011, 07:43 AM
If your already rendering at 16 bit float, then a good chance it is just your monitor. Remember that your monitor is typically only 6 or 8 bit. So the file format can store many more levels of color then your monitor can actually display.

My monitor is displaying 32bit color.

JLopezVFX
12-31-2011, 07:43 AM
Also be sure the file type in your render view is set to 32-bit in Maya (requires restart)

I made sure I did that as well.

Bitter
12-31-2011, 07:45 AM
Monitors tonemap to sRGB generally because they don't actually display all the information, hence the tonemapping.

JLopezVFX
12-31-2011, 07:56 AM
Monitors tonemap to sRGB generally because they don't actually display all the information, hence the tonemapping.

What do you suggest? I'm rendering in a linear workflow. Would any particular light cause banding? I'm using mostly area lights and one spot.


Update: It turns out I only get banding anytime I use a light that has falloff or in dark shadows.

Any fix for this?


https://lh3.googleusercontent.com/--zXpcsn-Nhs/Tv74b2TNbbI/AAAAAAAACrU/pi6oVRSvOlA/w531-h299-k/Banding_Bad_FallOFF.jpeg

stew
01-01-2012, 09:33 AM
What do you suggest? I'm rendering in a linear workflow. Would any particular light cause banding? I'm using mostly area lights and one spot.


Update: It turns out I only get banding anytime I use a light that has falloff or in dark shadows.

Any fix for this?


https://lh3.googleusercontent.com/--zXpcsn-Nhs/Tv74b2TNbbI/AAAAAAAACrU/pi6oVRSvOlA/w531-h299-k/Banding_Bad_FallOFF.jpeg
When converting from 16 bits/channel to 8 bits/channel, you need to add dithering. If and how you turn on dithering depends on the program that you use to do that conversion.

JLopezVFX
01-01-2012, 10:23 AM
When converting from 16 bits/channel to 8 bits/channel, you need to add dithering. If and how you turn on dithering depends on the program that you use to do that conversion.

Hi, Thank you for your response. I'm using Maya 2012 and dithering is on by default.
Any other ideas?

stew
01-01-2012, 07:10 PM
Hi, Thank you for your response. I'm using Maya 2012 and dithering is on by default.
Any other ideas?
If you're rendering to OpenEXR, Maya/MR is most likely not applying dithering. Whatever it is that turns your OpenEXR into PNG/TIFF/JPEG or other 8bit format needs to do the dithering, as the very last step in your pipeline.

JLopezVFX
01-02-2012, 01:07 AM
If you're rendering to OpenEXR, Maya/MR is most likely not applying dithering. Whatever it is that turns your OpenEXR into PNG/TIFF/JPEG or other 8bit format needs to do the dithering, as the very last step in your pipeline.

If anyone knows how to do that in Maya, PLEASE let me know.

I only see a check box in the render settings under framebuffer that says dither.
With that checked, nothing improves.

Bitter
01-02-2012, 01:12 AM
Can you post an example file of your workflow? This isn't something that should be a problem. For me it can be the result of a badly calibrated monitor with the brightness too high. But it should't be in the image itself like above.

Bitter
01-02-2012, 01:14 AM
Sidenote look at the blog in my signature at the latest post and there are similar images there. There is no banding.

ndeboar
01-02-2012, 03:26 AM
My Fix: Add a touch of noise in comp, even like 1% noise removes almost all banding from my renders.

JLopezVFX
01-02-2012, 10:10 AM
UPDATE: I dug deep into it and found out that I only get more banding when using 16bit - 32bit Frame buffer. There is not much banding in 8bit. This is a problem since I need to render with a 16bit frame buffer.

Bitter
01-02-2012, 10:13 AM
That makes no sense to me.

Use a 16-half framebuffer.

LEAVE THE GAMMA SETTING ALONE IN THE RENDER SETTINGS

Set your render view to use floating point (32-bit) and restart (required).

Then use the color management to select linear srgb as the image profile and srgb as the display. (renderview window)

Calibrate your monitor.

JLopezVFX
01-02-2012, 10:14 AM
Sidenote look at the blog in my signature at the latest post and there are similar images there. There is no banding.

Did you render those images in 8bit? I do see little banding on the dark end of the image.

Bitter
01-02-2012, 10:15 AM
They were saved to 8bit, what is your monitor brightness?

Bitter
01-02-2012, 10:17 AM
If you render to 8-bit you need to bake in the tonemapping with a lens shader, but then post operations won't work correctly.

JLopezVFX
01-02-2012, 10:17 AM
They were saved to 8bit, what is your monitor brightness?
Brightness is at 100% Why would that matter. You can see banding in my images right?

Bitter
01-02-2012, 10:20 AM
Brightness at 100% will enhance anything converted to display on your screen. (Meaning you will force artifacts in viewing)

In your area light examples it's very obvious but I think you're doing something strange or there's a bug.

Do you have that simple scene? I'd like to see what I can do to reproduce it.

JLopezVFX
01-02-2012, 10:20 AM
That makes no sense to me.

Use a 16-half framebuffer.

LEAVE THE GAMMA SETTING ALONE IN THE RENDER SETTINGS

Set your render view to use floating point (32-bit) and restart (required).

Then use the color management to select linear srgb as the image profile and srgb as the display. (renderview window)

Calibrate your monitor.

Exactly what I did.

JLopezVFX
01-02-2012, 10:22 AM
Brightness at 100% will enhance anything converted to display on your screen. (Meaning you will force artifacts in viewing)

In your area light examples it's very obvious but I think you're doing something strange or there's a bug.

Do you have that simple scene? I'd like to see what I can do to reproduce it.

Where can I send you .ma file?

Bitter
01-02-2012, 10:24 AM
You can zip a small one and put it on a file service. More people can get a looksee that way.

Mediafire, hotfile, whatever.

JLopezVFX
01-02-2012, 10:30 AM
You can zip a small one and put it on a file service. More people can get a looksee that way.

Mediafire, hotfile, whatever.

ok, on its way. Give me a min. and Thank you so much for your help.

JLopezVFX
01-02-2012, 10:35 AM
Sent to your email

Bitter
01-02-2012, 10:41 AM
Why are you using a portal light as a sky portal without a sun & sky system?

JLopezVFX
01-02-2012, 10:47 AM
Why are you using a portal light as a sky portal without a sun & sky system?

I set the Advanced Attribute to use Custom Environment with Lookup using FG Rays (Off)
I don't have to worry about ray traced shadow samples with this light.

Bitter
01-02-2012, 10:48 AM
http://hotfile.com/dl/139501050/7df4d0d/tiffComparison.zip.html

Few odd things going on here. Some of your settings are odd or unnecessary but shouldn't necessarily cause banding. However, look at the comparison with more normal settings and you'dd see banding is gone (at least on my monitor)

Bitter
01-02-2012, 10:49 AM
It's possible this is the cause of your banding but not sure. I relied on actual shadow settings and Unified Sampling.

Worked fine. Where did you get the idea to do that as a shadow hack?

JLopezVFX
01-02-2012, 10:54 AM
Yeah, I don't see banding on your image. Although the falloff is different. What settings did you change?

Bitter
01-02-2012, 10:58 AM
I ditched the portal light and just used the area light and changed the setting to quadratic. There's a bit of difference in intensity with that versus the portal light.

The portal light is useful for a lot of things and I know people use them for things. . .other than their intention. But in this case it causes artifacts. I wouldn't call it a bug because of how it is being used. In fact, that might be expected behavior when used like this.

I tend to follow the manual because I can't afford to miss a deadline for something odd. :shrug:

Bitter
01-02-2012, 11:01 AM
Sidenotes:

Your framebuffer is 16 short, that is incorrect. Make it 16 HALF
Your anti-aliasing is -1 1, that's low for a production test and might cause artifacts from aliasing.
Your filter is mitchell, it's strict. Good for print. Not really for animation or regular viewing on a screen in most cases. You need more samples to really make a strict filter work better and the payoff isn't always worth it.

If this is for a high quality still, then sure, but be sure you are getting enough samples.

JLopezVFX
01-02-2012, 11:02 AM
I ditched the portal light and just used the area light and changed the setting to quadratic. There's a bit of difference in intensity with that versus the portal light.

The portal light is useful for a lot of things and I know people use them for things. . .other than their intention. But in this case it causes artifacts. I wouldn't call it a bug because of how it is being used. In fact, that might be expected behavior when used like this.

I tend to follow the manual because I can't afford to miss a deadline for something odd. :shrug:

Can you send me the scene you did with no banding? I just tried the changes you've made and I still get banding.

Bitter
01-02-2012, 11:10 AM
Hold on, trying something else. . .

Bitter
01-02-2012, 11:15 AM
Ok, I think I see a problem. There's something odd in the Autodesk light shader. (color me surprised)

They do an odd trick that might cause this problem. (iRay doesn't do this, it's a shader by ARC)

If you're in Maya 2012 I'd suggest Unified Sampling and brute force (or nearly, lower the area light samples to 1-16, somewhere in there) and let Unified do the work. Looks better. The file attached has the options added automatically in the miDefaultOptions

Send the original file to AD and mark it as a deficiency in the light shader.

But the recommendation above with Unified is what I would do anyway.

http://hotfile.com/dl/139505016/2553beb/Banding_SceneB.mb.html

Bitter
01-02-2012, 11:30 AM
I know the next response to this will be "it takes longer" well yes, sphere on a plane will take longer at brute force. Switch off Unified and you'll see how nasty the regular AA looks, so you have an idea how much better Unified is by default.

I am currently rendering things that look like this (except CG, sorry, once the commercials are out I can point to them hopefully)Car Interior (http://images.newcars.com/images/car-pictures/original/2011-Hyundai-Equus-Sedan-Signature-4dr-Rear-wheel-Drive-Sedan-Interior.png) :

In about an hour a frame at HD resolution with brute force sampling, motion blur, and area lights. So it can be done and it looks good.

Rendered with Unified with a 10-15% savings per frame when we switched to brute force: http://www.hotwheels.com/videos/hot-wheels-action

I REALLY wish there was a high rez somewhere. If someone finds a high rez, please tell me! (It was rendered at 1080HD)

JLopezVFX
01-02-2012, 11:36 AM
What do you mean Unified? Where do you see switch for that?
And, what do you mean Brute force in this scene? Brute force is a term when dealing with G.I.

Bitter
01-02-2012, 11:47 AM
Brute Force can apply to other things than just GI. It means that sampling is done on a more 1 to 1 scale. Each sample taken takes one sample for say, reflection. Instead of 16 or 64, or whatever you have it set to. Even an area light where each ray traced back to the light is 1 at a time instead of 128 like your original scene.

Use this UI from Hans: http://forums.cgsociety.org/showthread.php?t=1018119

It exposes some things that will make your life much easier.

There are some changes we'd like to see made to this UI, but for now it works well to get people using more contemporary techniques. It automatically adds the options you would need to see these controls.

And it's 4am here, time for bed!

http://elementalray.wordpress.com/2011/11/30/unified-sampling-visually-for-the-artist/

(Unified Sampling)

JLopezVFX
01-02-2012, 11:57 AM
Awesome! Thank you for all your help.

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