linear workflow banding issues


#10

I’m not sure, but this may be the issue you guys are coming across:

When converting a floating point image to 8bit, if you don’t introduce any error diffusion (or dithering) you can end up with banding, which is really rounding issues on subtle gradients. It’ll look like this:

[](http://imageshack.us/photo/my-images/507/image1wcj.png/)[u]

[/u] However once you introduce some some error diffusion/dithering (which is really just noise), before converting to 8bit, it will fix the rounding issues and get rid of the banding:

A lot of programs like nuke do this inside the viewer (when its set to 8 bit), but I always add a dither node to clean it up for final output.


#11

Mercutio: Thank you for pointing that out. It seems that I have had dithering enabled the whole time, yet enabling it and disabling it between renders seems to make no noticeable difference.

My goal is to render out either RGBA 4x32bit float or RGBA 4x16bit half.

I think I have everything set up correctly, but Maya seems to be rendering in 8 bit regardless.

Either I have my settings wrong or Maya is ignoring them.

Is my set up wrong? If not do you guys know of a work around?

Thanks again!


#12

The dithering setting in maya seems to have no effect, in my example above, the renderview showed banding. The EXR file is actually fine with no banding. Take it into a compositing app, add dithering before you save it out to a 8bit format and it will be all good.


#13

Hi
I’m not sure if this can help, but do you have tiffLoader.mll and openEXRloader.mll loaded in your PLug-in Manager? also when saving as 32-bit-floating point HDR format, mental ray return this warning

// Warning: (Mayatomr.Scene) : output data type “rgba_fp” not directly supported by image format hdr, conversion performed by mental ray //
but the image is saved as 32 bit format, and no warning msg when saving other format like exr or tiff.
/Rachid


#14

The linear workflow system that it giving me banding problems is this one:

  • Use a 8bits texture with a full range from 0 to 1 (tiff, tga, png, jpg…).
  • Use a normal spotlight, or a physical sky (remember to change the gamma to 1 in camera lens)
  • Enable maya color management in the render settings, from sRGB to Linear. Change the framebuffer settings to RGBA Float (32bits), in the quality tab.
  • In the render view, in display, turn on 32 bits, and change color management to Linear to sRGB.
  • I notice banding effects and compression color artifacts in dark colors, with a value around 20-25%. In the render view and in batch rendered 32bits EXR.

To fix it, I have different possibilities:
First disable color management, and use one of those solutions:

  • EXR 32 bits textures instead of 8bits ones
  • use gamma correct node with the 8bits texture
  • Mental Core color management

Tomorrow I’ll post images and maybe a simple scene so you can try and check if I’m the only one having this problem.


#15

maybe this is a silly question, but just to be sure… did you set the framebuffer in the quality tab to rgba 4x32 float? (or half)


#16

Yes I did (forgot to write it in the description, I’m fixing that :wink: ).


#17

Well I’m glad at least that MentalCore solves this for you :thumbsup:


#18

Batch render is saving 32 bit tif files now, still seeing banding.

nookie: yep!

Archory: Yes I do have those plugins running, I’m not seeing that error, thanks for the input!

Mercutio: Thank you for the suggestion, adding dithering in after effects does seem to help a bit. Is there a way to smooth the noise?

What is mental core? Is there a demo available for mac?

chafouin: Thank you. I have noticed the banding is particularly strong in the darks of my ramp and in the darks of physical sky. We may have the the same problem. A scene set up would be particularly helpful, if you get a chance to put one together I would very much appreciate it.


#19

Here is an image to show the different results:

I redid the scene almost 10 times to be sure it wasn’t a stupid mistake from me. So either I just don’t know how to use maya color management (but this should be pretty straight forward), or there is a real bug here.


#20

If this is the most recent service pack of Maya 2012 you should report this as a bug to AD.

If you have a small test scene I’d like to test and send to my sources too for future builds.


#21

Would you mind sending me one of your 32bit files? Would be interesting to see.

Also if you want to check out mentalcore, goto http://core-cg.com - there are 30day trials avaliable for windows Mac and Linux


#22

You can get the scene file and the texture here: http://www.mediafire.com/?bwc3e21vce1pizq

Let me know if you find any mistake. I’m using maya 2012 with the Service pack.


#23

good to know!

here are my two most recent test files:

https://rapidshare.com/files/506605522/bandingTest5_persp.0.exr
https://rapidshare.com/files/952446803/bandingTest5_persp.0.tif

both are rendered using batch render, Maya’s color management and a gamma correct node of .454.


#24

Ok so I tested your scene, and the exr rendered out with Maya’s colour mangement is perfectly fine - even though it appears to be banding in the view port. This is the issue I was talking about earlier, obviously the renderview isn’t applying any dithering for floating point files.

If it take the rendered exr into nuke and switch the viewer to 32bit mode (8bit mode automatically applies dithering so you wont see banding) then I can clearly see the banding, applying a dither node at the end of the comp with really low values immediately makes the banding disappear.

[](http://imageshack.us/photo/my-images/198/dither.png/)

So the simple answer would be to say you can safely ignore any banding like this that you see in the renderview. It is not baked into the rendered file, its just how its being displayed - there’s no dithering being applied.


#25

Hey mercuito, thanks for having a look at the files.

Looking at rondobloodcannon images I totally agree with you that it is dithering problems, and I think you’ve got the solution to his problem.

But regarding my images, I’m not sure, but I think you misunderstood it :smiley: If you look at the top and at the bottom of the sphere you can see some terrible color artifacts, that only appear when using maya color management.


#26

Ah your totally right! I see it now! Sorry, my bad, I thought you were talking about the banding. Those colour artifacts are rather odd indeed!


#27

If you are suffering these banding issues when displaying your renders in Photoshop, turn of opengl drawing in your Photoshop prefs. That should remove all banding (display) issues.


#28

Dithering seems to be working quite well, thanks guys!


#29

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